Vintage Ford Intake Manifold CFM flow numbers

[shelbydoug]

I'm fairly certain from my conversations with Larry Ofria when I worked for him that Valley Head Service flowed the cylinder head intake manifold combination for the C6OE-A dual quad manifolds. Not necessarily for the numbers as to how well they were flowing but to make sure that they actually got the flow improvement that Shelby was paying for.

Later on in my conversations with Dan Case regarding the C6OA-E T/A intake he seemed to think that Mondello's head intake combination for the T/A intake was flowing better than the VHS combination.

The intakes were available in limited numbers to the Shelby people, definitely not available for Bud Moore's LM Cougar cars. The intakes provided to Shelby privateers were not modified by either VHS, Mondello, Charlie Slover or Ken Sperling. But out of the box.

I think that some of the numbers you are looking for are based on conjecture as the flow benches were not consistent with each other. Larry's VHS flow bench took up a whole room and was a magnificent piece of equipment. I never saw Mondello's or Ken Sperling's flow benches I saw Charlie Slover's bench but I doubt that the machines were as consistent as a modern flow bench mass produced. Even the modern flow benches have to be calibrated to get consistent numbers. For in house usage back in the day you could see on a port to port basis if the work you accomplished was a good result or not. However if you wanted to compare the intake manifold from this group to that group you would have had to choose one bench to use.


So even if you found the information you desire it would be junk compared to what you you could achieve today.


John

I appreciate the input.

In a recent/distant conversation with Curt Voght, in regards to the 620hp 292 "vintage" engines he was building, he mentioned that he was using the Blue Thunder Cobra high rise and extrude honing them.

A single 4v intake is a different animal, particularly when compared to the C60A.


The C60A in and of itself, is rather unique. It is a large port manifold, with equal length runners. The "tunnel ran" intakes were not yet in existance, but this manifold has some of the qualities of what would come to be common in tunnel rams.

In private discussions with "Randy", who was instrumental in me obtaining mine, we were discussing "desirable combinations" that would fall into the "desirable vintage" combinations.


One of the subjects was what effect on HP air flow had. Within that discussion were discussions of parts that at the time only "select race teams" like Shelby had access to.

One of those were the iron "GT40 heads". Something I still haven't seen in person and at the time I did not know existed?

Well to cut to the chase, the discussion revolved around what stock 289hp heads flow. 190cfm. What they flow race ported and dangerously thin, thought to be around 220cfm.

Then we had the iron GT40. Thought to be in the 240 vicinity as cast.

We never got to Webers or what that manifold could flow so no need to go there but I asked if he had an idea of the number a stock as cast C60A would show now and he thought 240. So complimentary to a GT40 head in his mind.


So we can get into what are good flow numbers are, etc., but with Curt's comments about extrude honing the "repro" Blue Thunders and considering how even "Vintage racers" attempt to "extend their advantages" and keep those largely unseen and the fact that Cobra Automotive dynos those engines at 620hp, the combination of all of this stirred my interest even more.

So knowingly that there are some reasonably accurate tested flow numbers available for heads now, I was just looking for those done on intakes. As always for comparative reasons.

Flow numbers are key indicators of the likely horsepower potential available. They are not ultimate's. There is enough "feeling in the field" for the adage that potential horsepower is often directly proportional to two times the cylinder head flow of one intake.

That much like the NHRA horsepower factors based upon vehicle weight, ET and trap speeds often seems more accurate then any advertised numbers.

I have only a limited experience with those factors but two comparisons that I remember were stock Boss429's being factored at 275hp and 428cj's at 400 usinf NHRA factor charts at the track.


I would say that my observation now is suspiciously indicative that the intake numbers even at this point are proprietary. Simply put, no one wants to talk about it even now. It is still a small group of numbers nerds? Very curious indeed. 

[JohnSlack]

I'm fairly certain from my conversations with Larry Ofria when I worked for him that Valley Head Service flowed the cylinder head intake manifold combination for the C6OE-A dual quad manifolds. Not necessarily for the numbers as to how well they were flowing but to make sure that they actually got the flow improvement that Shelby was paying for.

Later on in my conversations with Dan Case regarding the C6OA-E T/A intake he seemed to think that Mondello's head intake combination for the T/A intake was flowing better than the VHS combination.

The intakes were available in limited numbers to the Shelby people, definitely not available for Bud Moore's LM Cougar cars. The intakes provided to Shelby privateers were not modified by either VHS, Mondello, Charlie Slover or Ken Sperling. But out of the box.

I think that some of the numbers you are looking for are based on conjecture as the flow benches were not consistent with each other. Larry's VHS flow bench took up a whole room and was a magnificent piece of equipment. I never saw Mondello's or Ken Sperling's flow benches I saw Charlie Slover's bench but I doubt that the machines were as consistent as a modern flow bench mass produced. Even the modern flow benches have to be calibrated to get consistent numbers. For in house usage back in the day you could see on a port to port basis if the work you accomplished was a good result or not. However if you wanted to compare the intake manifold from this group to that group you would have had to choose one bench to use.


So even if you found the information you desire it would be junk compared to what you you could achieve today.


John

I appreciate the input.

In a recent/distant conversation with Curt Voght, in regards to the 620hp 292 "vintage" engines he was building, he mentioned that he was using the Blue Thunder Cobra high rise and extrude honing them.

A single 4v intake is a different animal, particularly when compared to the C60A.


The C60A in and of itself, is rather unique. It is a large port manifold, with equal length runners. The "tunnel ran" intakes were not yet in existance, but this manifold has some of the qualities of what would come to be common in tunnel rams.

In private discussions with "Randy", who was instrumental in me obtaining mine, we were discussing "desireable combinations" that would fall into the "desireable vintage" combinations.


One of the subjects was what effect on HP air flow had. Withing that discussion were discussions of parts that at the time only "select race teams" like Shelby had access to.

One of those were the iron "GT40 heads". Something I still haven't seen in person and at the time I did not know existed?

Well to cut to the chase, the discussion revolved around what stock 289hp heads flow. 190cfm. What they flow race pported and dangerously thin. 22cfm.

Then we had the iron GT40. Thought to be in the 240 vacinity.

We never got to Webers or what that manifold could flow so no need to go there but I asked if he had an idea of the number a stock C60A would show now and he theough 240. So complimentary to a GT40 head.


So we can get into what are good flow numbers are, etc., but with Curts comments about extrude honing his "repro" Blue Thunders and considering how even "Vintage racers" attempt to "extend their advantages" and keep those largely unseen and the fact that Cobra Automotive dynos those engines at 620hp, the combination of all of this stirred my interest even more.

So knowingly that there are some reasonably accurate tested flow numbers available for heads, I was just looking for those done on intakes.

Flow numbers are key indicators of the likely horespower potential available. They are not ultimates. There is enough "feeling in the field" for the adage that potential horsepower is often directly proportional to two times the cylinder head flow of one intake.

That much like the NHRA horsepower factors based upon vehicle weight, ET and trap speeds often seems more accurate then any advertised numbers.

I have only a limited experience with those factors but two comparisons that I remember were stock Boss429's being factored at 275hp and 428cj's at 400.


I would say that my observation now is suspiciously indicative that the intake numbers even at this point are proprietary. Simply put, no one wants to talk about it even now. Very curious indeed. 

I used to have a Superflow 600 bench. I can use per the deal of when I let it go to the new owner anytime I want. However now it is a 1,000 mile trip to where it is. I'm currently working on port matching a C6OE-A intake to a set of AFR cylinder heads for a 352" build on a Dart block. So I was pleased to see there was enough material to make the intake ports roughly a consistent 0.050" smaller all the way around.


We'll see how it goes.


John

[68countrysedan]

Two observations.

I suspect that NASCAR Cup teams have been all over intake manifold flow efficiency but I doubt they would ever reveal details.

As for selling magazines, one editor who I would trust to accurately explain flow details would have been Hot Rod's late Marlan Davis. Why he never did will never be known.

[shelbydoug]

I'm fairly certain from my conversations with Larry Ofria when I worked for him that Valley Head Service flowed the cylinder head intake manifold combination for the C6OE-A dual quad manifolds. Not necessarily for the numbers as to how well they were flowing but to make sure that they actually got the flow improvement that Shelby was paying for.

Later on in my conversations with Dan Case regarding the C6OA-E T/A intake he seemed to think that Mondello's head intake combination for the T/A intake was flowing better than the VHS combination.

The intakes were available in limited numbers to the Shelby people, definitely not available for Bud Moore's LM Cougar cars. The intakes provided to Shelby privateers were not modified by either VHS, Mondello, Charlie Slover or Ken Sperling. But out of the box.

I think that some of the numbers you are looking for are based on conjecture as the flow benches were not consistent with each other. Larry's VHS flow bench took up a whole room and was a magnificent piece of equipment. I never saw Mondello's or Ken Sperling's flow benches I saw Charlie Slover's bench but I doubt that the machines were as consistent as a modern flow bench mass produced. Even the modern flow benches have to be calibrated to get consistent numbers. For in house usage back in the day you could see on a port to port basis if the work you accomplished was a good result or not. However if you wanted to compare the intake manifold from this group to that group you would have had to choose one bench to use.


So even if you found the information you desire it would be junk compared to what you you could achieve today.


John

I appreciate the input.

In a recent/distant conversation with Curt Voght, in regards to the 620hp 292 "vintage" engines he was building, he mentioned that he was using the Blue Thunder Cobra high rise and extrude honing them.

A single 4v intake is a different animal, particularly when compared to the C60A.


The C60A in and of itself, is rather unique. It is a large port manifold, with equal length runners. The "tunnel ran" intakes were not yet in existance, but this manifold has some of the qualities of what would come to be common in tunnel rams.

In private discussions with "Randy", who was instrumental in me obtaining mine, we were discussing "desireable combinations" that would fall into the "desireable vintage" combinations.


One of the subjects was what effect on HP air flow had. Withing that discussion were discussions of parts that at the time only "select race teams" like Shelby had access to.

One of those were the iron "GT40 heads". Something I still haven't seen in person and at the time I did not know existed?

Well to cut to the chase, the discussion revolved around what stock 289hp heads flow. 190cfm. What they flow race pported and dangerously thin. 22cfm.

Then we had the iron GT40. Thought to be in the 240 vacinity.

We never got to Webers or what that manifold could flow so no need to go there but I asked if he had an idea of the number a stock C60A would show now and he theough 240. So complimentary to a GT40 head.


So we can get into what are good flow numbers are, etc., but with Curts comments about extrude honing his "repro" Blue Thunders and considering how even "Vintage racers" attempt to "extend their advantages" and keep those largely unseen and the fact that Cobra Automotive dynos those engines at 620hp, the combination of all of this stirred my interest even more.

So knowingly that there are some reasonably accurate tested flow numbers available for heads, I was just looking for those done on intakes.

Flow numbers are key indicators of the likely horespower potential available. They are not ultimates. There is enough "feeling in the field" for the adage that potential horsepower is often directly proportional to two times the cylinder head flow of one intake.

That much like the NHRA horsepower factors based upon vehicle weight, ET and trap speeds often seems more accurate then any advertised numbers.

I have only a limited experience with those factors but two comparisons that I remember were stock Boss429's being factored at 275hp and 428cj's at 400.


I would say that my observation now is suspiciously indicative that the intake numbers even at this point are proprietary. Simply put, no one wants to talk about it even now. Very curious indeed. 

I used to have a Superflow 600 bench. I can use per the deal of when I let it go to the new owner anytime I want. However now it is a 1,000 mile trip to where it is. I'm currently working on port matching a C6OE-A intake to a set of AFR cylinder heads for a 352" build on a Dart block. So I was pleased to see there was enough material to make the intake ports roughly a consistent 0.050" smaller all the way around.


We'll see how it goes.


John

I'm a C60A-A on a 347 with AFR heads. Somehow this monster likes BC-BD Holleys better then 2 1850's? I suspect there is quite a better flow in the as cast manifold then Mr.Gillis suggested to me of 240cfm per cylinder?

Kind of difficult to take a virtually new intake and risk an Extrude Hone, especially if there is no reason to do it.

If you are talking about the wall thickness of the intake runners on the C60E-A, at .050" thick, that is my concern with touching anything but gasket matching them. In my case with my combination, as cast on the manifold and as delivery CNC ported by AFR, that is not necessary as is.

In leu of comparative flow numbers for either of those intakes (presuming the C60A-A and the C60E-A are identical) the only reasonable place to improve them seems to be in smoothing the plenum to port transitions internally. For me, best to leave the thing alone.

[JohnSlack]

I'm fairly certain from my conversations with Larry Ofria when I worked for him that Valley Head Service flowed the cylinder head intake manifold combination for the C6OE-A dual quad manifolds. Not necessarily for the numbers as to how well they were flowing but to make sure that they actually got the flow improvement that Shelby was paying for.

Later on in my conversations with Dan Case regarding the C6OA-E T/A intake he seemed to think that Mondello's head intake combination for the T/A intake was flowing better than the VHS combination.

The intakes were available in limited numbers to the Shelby people, definitely not available for Bud Moore's LM Cougar cars. The intakes provided to Shelby privateers were not modified by either VHS, Mondello, Charlie Slover or Ken Sperling. But out of the box.

I think that some of the numbers you are looking for are based on conjecture as the flow benches were not consistent with each other. Larry's VHS flow bench took up a whole room and was a magnificent piece of equipment. I never saw Mondello's or Ken Sperling's flow benches I saw Charlie Slover's bench but I doubt that the machines were as consistent as a modern flow bench mass produced. Even the modern flow benches have to be calibrated to get consistent numbers. For in house usage back in the day you could see on a port to port basis if the work you accomplished was a good result or not. However if you wanted to compare the intake manifold from this group to that group you would have had to choose one bench to use.


So even if you found the information you desire it would be junk compared to what you you could achieve today.


John

I appreciate the input.

In a recent/distant conversation with Curt Voght, in regards to the 620hp 292 "vintage" engines he was building, he mentioned that he was using the Blue Thunder Cobra high rise and extrude honing them.

A single 4v intake is a different animal, particularly when compared to the C60A.


The C60A in and of itself, is rather unique. It is a large port manifold, with equal length runners. The "tunnel ran" intakes were not yet in existance, but this manifold has some of the qualities of what would come to be common in tunnel rams.

In private discussions with "Randy", who was instrumental in me obtaining mine, we were discussing "desireable combinations" that would fall into the "desireable vintage" combinations.


One of the subjects was what effect on HP air flow had. Withing that discussion were discussions of parts that at the time only "select race teams" like Shelby had access to.

One of those were the iron "GT40 heads". Something I still haven't seen in person and at the time I did not know existed?

Well to cut to the chase, the discussion revolved around what stock 289hp heads flow. 190cfm. What they flow race pported and dangerously thin. 22cfm.

Then we had the iron GT40. Thought to be in the 240 vacinity.

We never got to Webers or what that manifold could flow so no need to go there but I asked if he had an idea of the number a stock C60A would show now and he theough 240. So complimentary to a GT40 head.


So we can get into what are good flow numbers are, etc., but with Curts comments about extrude honing his "repro" Blue Thunders and considering how even "Vintage racers" attempt to "extend their advantages" and keep those largely unseen and the fact that Cobra Automotive dynos those engines at 620hp, the combination of all of this stirred my interest even more.

So knowingly that there are some reasonably accurate tested flow numbers available for heads, I was just looking for those done on intakes.

Flow numbers are key indicators of the likely horespower potential available. They are not ultimates. There is enough "feeling in the field" for the adage that potential horsepower is often directly proportional to two times the cylinder head flow of one intake.

That much like the NHRA horsepower factors based upon vehicle weight, ET and trap speeds often seems more accurate then any advertised numbers.

I have only a limited experience with those factors but two comparisons that I remember were stock Boss429's being factored at 275hp and 428cj's at 400.


I would say that my observation now is suspiciously indicative that the intake numbers even at this point are proprietary. Simply put, no one wants to talk about it even now. Very curious indeed. 

I used to have a Superflow 600 bench. I can use per the deal of when I let it go to the new owner anytime I want. However now it is a 1,000 mile trip to where it is. I'm currently working on port matching a C6OE-A intake to a set of AFR cylinder heads for a 352" build on a Dart block. So I was pleased to see there was enough material to make the intake ports roughly a consistent 0.050" smaller all the way around.


We'll see how it goes.


John

I'm

I'm fairly certain from my conversations with Larry Ofria when I worked for him that Valley Head Service flowed the cylinder head intake manifold combination for the C6OE-A dual quad manifolds. Not necessarily for the numbers as to how well they were flowing but to make sure that they actually got the flow improvement that Shelby was paying for.

Later on in my conversations with Dan Case regarding the C6OA-E T/A intake he seemed to think that Mondello's head intake combination for the T/A intake was flowing better than the VHS combination.

The intakes were available in limited numbers to the Shelby people, definitely not available for Bud Moore's LM Cougar cars. The intakes provided to Shelby privateers were not modified by either VHS, Mondello, Charlie Slover or Ken Sperling. But out of the box.

I think that some of the numbers you are looking for are based on conjecture as the flow benches were not consistent with each other. Larry's VHS flow bench took up a whole room and was a magnificent piece of equipment. I never saw Mondello's or Ken Sperling's flow benches I saw Charlie Slover's bench but I doubt that the machines were as consistent as a modern flow bench mass produced. Even the modern flow benches have to be calibrated to get consistent numbers. For in house usage back in the day you could see on a port to port basis if the work you accomplished was a good result or not. However if you wanted to compare the intake manifold from this group to that group you would have had to choose one bench to use.


So even if you found the information you desire it would be junk compared to what you you could achieve today.


John

I appreciate the input.

In a recent/distant conversation with Curt Voght, in regards to the 620hp 292 "vintage" engines he was building, he mentioned that he was using the Blue Thunder Cobra high rise and extrude honing them.

A single 4v intake is a different animal, particularly when compared to the C60A.


The C60A in and of itself, is rather unique. It is a large port manifold, with equal length runners. The "tunnel ran" intakes were not yet in existance, but this manifold has some of the qualities of what would come to be common in tunnel rams.

In private discussions with "Randy", who was instrumental in me obtaining mine, we were discussing "desireable combinations" that would fall into the "desireable vintage" combinations.


One of the subjects was what effect on HP air flow had. Withing that discussion were discussions of parts that at the time only "select race teams" like Shelby had access to.

One of those were the iron "GT40 heads". Something I still haven't seen in person and at the time I did not know existed?

Well to cut to the chase, the discussion revolved around what stock 289hp heads flow. 190cfm. What they flow race pported and dangerously thin. 22cfm.

Then we had the iron GT40. Thought to be in the 240 vacinity.

We never got to Webers or what that manifold could flow so no need to go there but I asked if he had an idea of the number a stock C60A would show now and he theough 240. So complimentary to a GT40 head.


So we can get into what are good flow numbers are, etc., but with Curts comments about extrude honing his "repro" Blue Thunders and considering how even "Vintage racers" attempt to "extend their advantages" and keep those largely unseen and the fact that Cobra Automotive dynos those engines at 620hp, the combination of all of this stirred my interest even more.

So knowingly that there are some reasonably accurate tested flow numbers available for heads, I was just looking for those done on intakes.

Flow numbers are key indicators of the likely horespower potential available. They are not ultimates. There is enough "feeling in the field" for the adage that potential horsepower is often directly proportional to two times the cylinder head flow of one intake.

That much like the NHRA horsepower factors based upon vehicle weight, ET and trap speeds often seems more accurate then any advertised numbers.

I have only a limited experience with those factors but two comparisons that I remember were stock Boss429's being factored at 275hp and 428cj's at 400.


I would say that my observation now is suspiciously indicative that the intake numbers even at this point are proprietary. Simply put, no one wants to talk about it even now. Very curious indeed. 

I used to have a Superflow 600 bench. I can use per the deal of when I let it go to the new owner anytime I want. However now it is a 1,000 mile trip to where it is. I'm currently working on port matching a C6OE-A intake to a set of AFR cylinder heads for a 352" build on a Dart block. So I was pleased to see there was enough material to make the intake ports roughly a consistent 0.050" smaller all the way around.


We'll see how it goes.


John

I'm a C60A-A on a 347 with AFR heads. Somehow this monster likes BC-BD Holleys better then 2 1850's? I suspect there is quite a better flow then Mr.Gillis suggested?

Kind of difficult to take a virtually new intake and risk an Extrude Hone, especially if there is no reason to do it.

I'm fairly certain from my conversations with Larry Ofria when I worked for him that Valley Head Service flowed the cylinder head intake manifold combination for the C6OE-A dual quad manifolds. Not necessarily for the numbers as to how well they were flowing but to make sure that they actually got the flow improvement that Shelby was paying for.

Later on in my conversations with Dan Case regarding the C6OA-E T/A intake he seemed to think that Mondello's head intake combination for the T/A intake was flowing better than the VHS combination.

The intakes were available in limited numbers to the Shelby people, definitely not available for Bud Moore's LM Cougar cars. The intakes provided to Shelby privateers were not modified by either VHS, Mondello, Charlie Slover or Ken Sperling. But out of the box.

I think that some of the numbers you are looking for are based on conjecture as the flow benches were not consistent with each other. Larry's VHS flow bench took up a whole room and was a magnificent piece of equipment. I never saw Mondello's or Ken Sperling's flow benches I saw Charlie Slover's bench but I doubt that the machines were as consistent as a modern flow bench mass produced. Even the modern flow benches have to be calibrated to get consistent numbers. For in house usage back in the day you could see on a port to port basis if the work you accomplished was a good result or not. However if you wanted to compare the intake manifold from this group to that group you would have had to choose one bench to use.


So even if you found the information you desire it would be junk compared to what you you could achieve today.


John

I appreciate the input.

In a recent/distant conversation with Curt Voght, in regards to the 620hp 292 "vintage" engines he was building, he mentioned that he was using the Blue Thunder Cobra high rise and extrude honing them.

A single 4v intake is a different animal, particularly when compared to the C60A.


The C60A in and of itself, is rather unique. It is a large port manifold, with equal length runners. The "tunnel ran" intakes were not yet in existance, but this manifold has some of the qualities of what would come to be common in tunnel rams.

In private discussions with "Randy", who was instrumental in me obtaining mine, we were discussing "desireable combinations" that would fall into the "desireable vintage" combinations.


One of the subjects was what effect on HP air flow had. Withing that discussion were discussions of parts that at the time only "select race teams" like Shelby had access to.

One of those were the iron "GT40 heads". Something I still haven't seen in person and at the time I did not know existed?

Well to cut to the chase, the discussion revolved around what stock 289hp heads flow. 190cfm. What they flow race pported and dangerously thin. 22cfm.

Then we had the iron GT40. Thought to be in the 240 vacinity.

We never got to Webers or what that manifold could flow so no need to go there but I asked if he had an idea of the number a stock C60A would show now and he theough 240. So complimentary to a GT40 head.


So we can get into what are good flow numbers are, etc., but with Curts comments about extrude honing his "repro" Blue Thunders and considering how even "Vintage racers" attempt to "extend their advantages" and keep those largely unseen and the fact that Cobra Automotive dynos those engines at 620hp, the combination of all of this stirred my interest even more.

So knowingly that there are some reasonably accurate tested flow numbers available for heads, I was just looking for those done on intakes.

Flow numbers are key indicators of the likely horespower potential available. They are not ultimates. There is enough "feeling in the field" for the adage that potential horsepower is often directly proportional to two times the cylinder head flow of one intake.

That much like the NHRA horsepower factors based upon vehicle weight, ET and trap speeds often seems more accurate then any advertised numbers.

I have only a limited experience with those factors but two comparisons that I remember were stock Boss429's being factored at 275hp and 428cj's at 400.


I would say that my observation now is suspiciously indicative that the intake numbers even at this point are proprietary. Simply put, no one wants to talk about it even now. Very curious indeed. 

I used to have a Superflow 600 bench. I can use per the deal of when I let it go to the new owner anytime I want. However now it is a 1,000 mile trip to where it is. I'm currently working on port matching a C6OE-A intake to a set of AFR cylinder heads for a 352" build on a Dart block. So I was pleased to see there was enough material to make the intake ports roughly a consistent 0.050" smaller all the way around.


We'll see how it goes.


John

I'm a C60A-A on a 347 with AFR heads. Somehow this monster likes BC-BD Holleys better then 2 1850's? I suspect there is quite a better flow then Mr.Gillis suggested?

Kind of difficult to take a virtually new intake and risk an Extrude Hone, especially if there is no reason to do it.

a C60A-A on a 347 with AFR heads. Somehow this monster likes BC-BD Holleys better then 2 1850's? I suspect there is quite a better flow then Mr.Gillis suggested?

Kind of difficult to take a virtually new intake and risk an Extrude Hone, especially if there is no reason to do it.

Agreed on the extrude hone, especially if you look inside and study what is there.


John

[shelbydoug]

Yes. What I am seeing is a very close to equal length manifold at wide open throttle The length from throttle plate to intake valve at what is now derived at as optimal and a very high quality casting (almost pressure cast) with close to perfect shape internal ports their entire lengths, port exit shapes with a near perfect gasket match as cast and last but not least, internal port passages that match the OD of the BC-BD Holleys/

The accuracy of the casting is amazing and it was not cast up in someones back yard sand box. The pattern probably belongs in a modern industrial art museum. This manifold is serious stuff.

I doubt that it could be improved upon. Only ruined.

Without having my own flow bench, it just raises my level of curiosity at exactly what I am dealing with? Maybe an Area 51, reverse engineered Alien design? I've never seen anything from that era that even approaches this kind of accuracy in a casting and anything coming close to optimization like this?

It is almost a shame to get it dirty but almost impossible to resist running this mutha'?


The issue of #5 running lean on the "turd" eliminated. The only possible area to mess with is the plenum balance tube which is reduced in size from the WOT runners. I wouldn't even mess with that since it probably is already a balance of compromises to make the thing acceptable for idle and part throttle. There I wouldn't be shocked if the other variants were experimented with and vary?

This was not arrived at by guessing. Someone had a flow bench and wasn't using just a slide rule to analyze the results.

But as suggested, it was analyzed as a system with the heads but there is a suggestion to me that it may be partially a variable flow design because of the balance tube? Aliens can be strange.

I'm guessing it is closer to 280 cfm (perhaps  more) as a system which would make sense of why it runs so well at just off idle and part throttle on the BC-BD's and plays well with the AFR heads? Those were also Randy's suggestion.

The fact that all of the original design considerations were for maximizing 289's and this is one is on a 347 doesn't hurt the equation either, just makes everything more responsive to throttle input. The increase in engine cubic inches from 289 to 347 works in bring down rpm peaks to a more streetable number and out of the 8,000 rpm stratosphere.


Some ask why use a dual 4 when recent dynos show little benefit over a single 4? Something like 15hp more. It may be that 2-4's gives opportunity to better runner layout that a single 4 can't and that shows in much less cylinder to cylinder flow variation as cast? That is why I would be interesting to see what the single 4v Cobra, etc., does on a flow bench, stock and then modified.

Look at how the Torker and the Rousch attempt to equalize the runner lengths on a single 4.

[Royce Peterson]

I searched everywhere with no results at all.

Have any of you found a source publishing tested results of '60s Ford performance intake manifolds CFM flow numbers? I can't find anything.

Head flow numbers are by comparison easy to find.

Have any of you done Extrude Hone on any of the intakes?


I seem to remember Cobra Automotive offering Extrude Hone on the Cobra high rise intakes but haven't talked to them recently about it.

I helped run dozens of FE intakes that Jay Brown used the results of to write his book "The Great FE Intake Comparo". If you use an FE in anything you need to read this book.

[pbf777]

The only possible area to mess with is the plenum balance tube which is reduced in size from the WOT runners. I wouldn't even mess with that since it probably is already a balance of compromises to make the thing acceptable for idle and part throttle.

    Yes, the "balance tube" is a compromise development particularly attributed to the progressive carburetor linkage function, but to some degree is also utilized in aiding in balancing the flow sums more equally particularly between the two carburetors but also thought the intake manifold at W.O.T.. 

    This probably indicating that if utilizing, say.............a pair of Holley List #4224, 660 C.F.M. "Center-Squirters", with 1 : 1 throttle linkage setup, and with testing, the balance or cross-over passage would probably be found to be excessively generous in size for "best performance". 

Some ask why use a dual 4 when recent dynos show little benefit over a single 4? It may be that 2-4's gives opportunity to better runner layout that a single 4 can't and that shows in much less cylinder to cylinder flow variation..........

    One would need to quantify the first sentence to some degree in order to avoid an argument; but the next is absolutely a contributing factor!   

The fact that all of the original design considerations were for maximizing 289's and this is one is on a 347 doesn't hurt the equation either, just makes everything more responsive to throttle input.

    Well yes,............ but if the induction were truly "maximized" for an engine capacity of 289 cu.in.'s, then mounting such on an engine of 347 cu.in. 'is' going to change the experienced performance throughout the dynamic range of operation; probably simply put, one would expect greater throttle response and torque in the lower R.P.M. ranges, but with lesser peak R.P.M.'s for useful power production, and in the end 'perhaps', though at a lower R.P.M. for the latter, both engine examples may prove only equivalent in peak horsepower numbers. 

    Scott.

[shelbydoug]

The only possible area to mess with is the plenum balance tube which is reduced in size from the WOT runners. I wouldn't even mess with that since it probably is already a balance of compromises to make the thing acceptable for idle and part throttle.

    Yes, the "balance tube" is a compromise development particularly attributed to the progressive carburetor linkage function, but to some degree is also utilized in aiding in balancing the flow sums more equally particularly between the two carburetors but also thought the intake manifold at W.O.T.. 

    This probably indicating that if utilizing, say.............a pair of Holley List #4224, 660 C.F.M. "Center-Squirters", with 1 : 1 throttle linkage setup, and with testing, the balance or cross-over passage would probably be found to be excessively generous in size for "best performance". 

Some ask why use a dual 4 when recent dynos show little benefit over a single 4? It may be that 2-4's gives opportunity to better runner layout that a single 4 can't and that shows in much less cylinder to cylinder flow variation..........

    One would need to quantify the first sentence to some degree in order to avoid an argument; but the next is absolutely a contributing factor!   

The fact that all of the original design considerations were for maximizing 289's and this is one is on a 347 doesn't hurt the equation either, just makes everything more responsive to throttle input.

    Well yes,............ but if the induction were truly "maximized" for an engine capacity of 289 cu.in.'s, then mounting such on an engine of 347 cu.in. 'is' going to change the experienced performance throughout the dynamic range of operation; probably simply put, one would expect greater throttle response and torque in the lower R.P.M. ranges, but with lesser peak R.P.M.'s for useful power production, and in the end 'perhaps', though at a lower R.P.M. for the latter, both engine examples may prove only equivalent in peak horsepower numbers. 

    Scott.

Well I have no idea if the manifold actually maximized intake performance for a 289 but considering how experimentation is progressive and I see no "bigger attempt" I ASSUME that there was no "next step up" UNLESS there is and that is the dual Dominators on the Boss 302?-


In my case since this is a street car and I don't need to fight  (or pay for) minute increases in horsepower to fend off the competition, reaching maximum power and torque at a lower rpm then the seeming suicidal T/A racers of the day is a definite benefit to me. That is why I selected 347ci instead of 331 (or 289 or 302).
I don't need an 8,000 rpm limit and certainly the repair bills that will come with attempting to use that.

On that subject, however, it seems likely to me, that this setup liking the BC-BD, 715cfm carbs may be because of the larger displacement? The inside diameter of the intake runners suggests at least to me that there was design consideration for something more then 1850's. These runners match the throttle bores of the 3300/3301's.


It may have wound up with a pair of 1:1 660 center squirters but that was a later development. Not the initial application. It wasn't designed for those carbs because they didn't exist when it was. It had a pair of vacuum secondaries. Drivers complained that the vacuum secondaries didn't respond fast enough to closing the throttle. So Ford brought in Holley to fix the issue and inventing the 660's was that solution.


I suspect that there can be a "sweet spot" where the larger runners will work for both the 289 displacement and something larger. Velocity and volume are both maintained. That could be accidental but this thing is no less then an Alien Device with properties where the sum of the parts is greater then the whole?

This manifold was inarguably created with data beyond the realm of even super human abilities. Possibly the formula was accidentally found in the Akoshic Records that the Hindus speak of?


If I had infinite time and financing to experiment endlessly, it certainly would result in more data available to suggest if not prove exactly what is going on and why, but needless to say, I don't.

So I'm happy with the positive results considering that it could have been a terrible mismatch.

Again, it would be enlightening to see flow bench results on this setup? Something good is going on here.



I suppose I am like the Wizard of Oz in that I just came here in a hot air balloon that someone else built, but I don't know how the thing works and can't fix it?

Life is strange. Me too.

[JohnSlack]

I agree that with a lower RPM limit theoretically on a larger engine you are playing in the same ballpark. As an example a 289 CID engine @ 8,000 RPM in theory flows as much at WOT as a 347 CID engine @ roughly 6,600 RPM. A much more reasonable number for a street car. However knowing you, you probably push another 400 RPM for a still reasonable 7,000 RPM redline.

The Harold Drost Holley carburetors (Sorry Randy, we must share the conversation with a larger audience now that you have passed. I kept my end of the bargain.) prior to the double pumper were a progressive linkage center squirter carburetor. These as you alluded to, work better than the vacuum secondary carburetors on deceleration and that is an important aspect of the functioning of the engine. In addition the Drost/Holley carburetors were smaller in CFM than the 660 carburetors, at around 590 CFM with bushed shafts and a special groove cut into the throttle actuating cam to provide a progressive linkage for increased on track drivability.  With a 20% larger engine and a 6,500 to 7,000 RPM redline my guess is that you are going in a great direction with the BC/BD carburetors.

As to "I ASSUME that there was no "next step up" UNLESS there is and that is the dual Dominators on the Boss 302?" That was really FoMoCo trying a work around on the "no Weber policy" the SCCA had with Trans Am. If you use the Weber formula with the 305 cubic inch 8,000 RPM input of the T/A BOSS 302 engine you will see that the big 1150 CFM carburetors fit the bill. Next step is to realize that in an IR application the depression on the venturing booster is roughly half of what it is in a plenum style intake system. Therefore those big old bad dominators are only flowing 575 CFM on the dual dominator intake manifold.... 🤔 Hmmm, pretty darn close to the 590 CFM carburetors I mentioned previously that were developed for the 302 Tunnelport and GT40 programs. So not actually as big a "Step Up" as it was a "how does this work" trial for the Trans Am series. As a side note Randy shared with me that in tests with multiple engines and intake manifold combinations in the same chassis after the 1968 season the drivers actually preferred the standard flange Holley dual plane/dual quad intake manifold with the 590 CFM carburetors on the BOSS 302 engine to the Dual Dominator equipped BOSS 302 engines. The theory is that the bean counters in Dearborn said that with all the funds invested in the Dominator system and since the max horsepower numbers were comparable the standard flange Holley dual plane/dual quad intake was not made a production part. Neither Randy or myself ever saw or knew of anyone who saw one of those intake manifolds with even an SK number cast into it. Only 10 were known to exist as of Randy's and my last big search. Yes it works far superior to the Shelby dual plane/dual quad BOSS 302 intake that more closely resembles the C6OE-A intake manifold that it was most likely developed from and requires an offset distributor as well.

In an unlimited time and money budget world I as well would be chasing more answers. For now I'm working on a 352 inch motor with the C6OE-A, an undetermined CID BOSS motor with the 1969 T/A intakes, and a 302 CID motor with Kelly Coffield's long runner IR Dual "B" Inline carburetor intake manifold. I'm sure I will still be looking for answers for a long long time. FoMoCo had more smarter folks than me, a bunch more of them than I do.


John

[shelbydoug]

I agree that with a lower RPM limit theoretically on a larger engine you are playing in the same ballpark. As an example a 289 CID engine @ 8,000 RPM in theory flows as much at WOT as a 347 CID engine @ roughly 6,600 RPM. A much more reasonable number for a street car. However knowing you, you probably push another 400 RPM for a still reasonable 7,000 RPM redline.

The Harold Drost Holley carburetors (Sorry Randy, we must share the conversation with a larger audience now that you have passed. I kept my end of the bargain.) prior to the double pumper were a progressive linkage center squirter carburetor. These as you alluded to, work better than the vacuum secondary carburetors on deceleration and that is an important aspect of the functioning of the engine. In addition the Drost/Holley carburetors were smaller in CFM than the 660 carburetors, at around 590 CFM with bushed shafts and a special groove cut into the throttle actuating cam to provide a progressive linkage for increased on track drivability.  With a 20% larger engine and a 6,500 to 7,000 RPM redline my guess is that you are going in a great direction with the BC/BD carburetors.

As to "I ASSUME that there was no "next step up" UNLESS there is and that is the dual Dominators on the Boss 302?" That was really FoMoCo trying a work around on the "no Weber policy" the SCCA had with Trans Am. If you use the Weber formula with the 305 cubic inch 8,000 RPM input of the T/A BOSS 302 engine you will see that the big 1150 CFM carburetors fit the bill. Next step is to realize that in an IR application the depression on the venturing booster is roughly half of what it is in a plenum style intake system. Therefore those big old bad dominators are only flowing 575 CFM on the dual dominator intake manifold.... 🤔 Hmmm, pretty darn close to the 590 CFM carburetors I mentioned previously that were developed for the 302 Tunnelport and GT40 programs. So not actually as big a "Step Up" as it was a "how does this work" trial for the Trans Am series. As a side note Randy shared with me that in tests with multiple engines and intake manifold combinations in the same chassis after the 1968 season the drivers actually preferred the standard flange Holley dual plane/dual quad intake manifold with the 590 CFM carburetors on the BOSS 302 engine to the Dual Dominator equipped BOSS 302 engines. The theory is that the bean counters in Dearborn said that with all the funds invested in the Dominator system and since the max horsepower numbers were comparable the standard flange Holley dual plane/dual quad intake was not made a production part. Neither Randy or myself ever saw or knew of anyone who saw one of those intake manifolds with even an SK number cast into it. Only 10 were known to exist as of Randy's and my last big search. Yes it works far superior to the Shelby dual plane/dual quad BOSS 302 intake that more closely resembles the C6OE-A intake manifold that it was most likely developed from and requires an offset distributor as well.

In an unlimited time and money budget world I as well would be chasing more answers. For now I'm working on a 352 inch motor with the C6OE-A, an undetermined CID BOSS motor with the 1969 T/A intakes, and a 302 CID motor with Kelly Coffield's long runner IR Dual "B" Inline carburetor intake manifold. I'm sure I will still be looking for answers for a long long time. FoMoCo had more smarter folks than me, a bunch more of them than I do.


John

If the 3300/3301 turn out to be unrealistic somehow, the 1850's are fine. It seems ironic that they actually idle much better and are smoother? Go figure?
I have them off right now and the 1850's on just because I can't believe that they can possibly be right? Even after driving the car, but the 1850' just don't pull as hard.


Randy did warn me about the Shelby dual 4 B2 intake. He said "it didn't work. Don't bother to go that way".


I'm not sure that anyone can prove why any of these work, just theorize why they do. I'm thinking that there was more development work needed to do to make the B2 version work with the balance tube. I think that is the tuneable part?


I'm sure that all of us are influenced by some of the  "racer's adages" simply because there is a lot of mileage and experience that went into those conclusions even though they couldn't work a slide rule.

Two that I can think of is that "air flow x2 = horsepower" and "carb cfm = 2x cid". Those numbers seem to agree more times then not?


Although I admit that you have correctly surmised my rpm thinking I am like the comedian Robert Klein in that "I can't stop my foot". It simply has a mind of its own so the only safe thing to do is an rpm limiter and "safe valve springs".

I miss Randy too. He was on my case to bring my car to the west coast. He wanted to see it run but I think he just wanted to race me. He kept threatening me with unrealistic classifications where essentially I'd be running against Pro-stock like modified cars. He said mine was just to modified to let run against stockish GT350's, the SOB! 


After "playing" with these cars for over 50 years, I've constantly had to reinvent myself to keep interested. At this point the C60A has just run fresh blood into the old veins. To think that the tech crews that designed, built, developed and immortalized things like this were living back then on probably a $150 a week pay day is just incredible.


Even Elton John dreamed about those days when he sang to Marilyn Monroe. "I would have loved to love you but I was just a kid". And he is gay. So those days fascinate many of us even in unrealistic ways?

It was just a fascinating time. It encourages me to realize that we are still living in a golden age and for me pulling something of this level out of a time machine gave me a new burst of energy?


I went with Webers on my Pantera. I had a B2 Doug Nash magnesium split intake but I couldn't nail down a pair of inlines. Kelly would buy them out from under me. Ancient history and sent me to the Weber route. That was 1978ish. No regrets.


I can say that what I found with the 351c, that a 4779 750dp was just a bit large for it. A 700dp was about right but the Boss 302 735cfm Holley with the vacuum secondary wasn't right either. It wasn't as responsive as the DP was.

Presuming that a 350ci engine is about right with a 700ish carb. Running with the BC/BD's I can see where they are working as a "700 something dp" with afterburners? I can hear the secondaries open and they make a heck of a racket when they do. You can see the nose of the car coming up. It's just a little bit violent, shudders the car and it kind of reminds me of how "slick shake", shakes the car? So I do not think it is over carbed at all.

IF we are speculating on why the big carbs work on the 347, 1.2 x 590 = 708. That is suggestive of what is going on and why the big carbs are working.
I can't think of an equation that predicts the level of my irrationality at this moment? Maybe someone else can?

Why the BC/BD idle better and have better part throttle manors was suggested by Drew in that they have the ideal ratio of venturi size to throttle bore.


Is there a difference between the C60A and the C60E besides the casting numbers and for that matter the SHELBY tagged no numbers version? Besides the casting ID's, the outside looks the same? Does the internal size of the balance tube vary?


I feel like Indiana Jones discovering a long abandoned "City of Gold" built by a higher level of technology that somehow has been lost over the decades?


All very interesting and definitely going to keep me busy for quite a while. Now it has me thinking if the camshaft is optimized and I think I am one level small on that? It never stops I suppose until you are dead?
Oh, this is an A/C car too. It's no wonder the neighbors are all terrorized by the old guy with the long grey hair. "Better be nice to him. Might be one of those radical '60s 'Hippies'?"

[pbf777]

Next step is to realize that in an IR application the depression on the venturing booster is roughly half of what it is in a plenum style intake system. Therefore those big old bad dominators are only flowing 575 CFM on the dual dominator intake manifold.... 🤔 Hmmm, pretty darn close to the 590 CFM carburetors I mentioned previously that were developed for the 302 Tunnelport and GT40 programs. So not actually as big a "Step Up" as it was a "how does this work" trial for the Trans Am series.

    John,

    I'm not sure that I'm reading this statement as you might have meant it to be understood (and of course, this may solely be me ); this as in the the "peak" depression value as experienced through the carburetor venturi, and hence acting upon the booster venturi, of the I.R. manifolding is generally significantly greater than that of the plenum style induction manifolds; but obviously isn't as constant, with reversals that often spike the pressure through the venturi's above atmospheric, again to sums far greater than that of the latter.

    But I suppose, if one were to average these values over a duration of time, then perhaps the meaning in your statement might prove more relevant.  As if the same engine produces approximately the same H.P., even with two different induction systems, then the total air flow sums here, in general, are considered pretty much a constant. But in the instance of the I.R. induction system, with the lack of a plenum effect and volume, this sum of atmosphere volume must pass through the venturi in less time.   

    Scott.

[NukeGT]

This video about flow testing a Shelby COBRA intake manifold although modified with porting may be of interest to some.

https://youtu.be/wZ-ZW2J3Occ?si=9A5TqrRl_Mb-qUj9

[JohnSlack]

Next step is to realize that in an IR application the depression on the venturing booster is roughly half of what it is in a plenum style intake system. Therefore those big old bad dominators are only flowing 575 CFM on the dual dominator intake manifold.... 🤔 Hmmm, pretty darn close to the 590 CFM carburetors I mentioned previously that were developed for the 302 Tunnelport and GT40 programs. So not actually as big a "Step Up" as it was a "how does this work" trial for the Trans Am series.

    John,

    I'm not sure that I'm reading this statement as you might have meant it to be understood (and of course, this may solely be me ); this as in the the "peak" depression value as experienced through the carburetor venturi, and hence acting upon the booster venturi, of the I.R. manifolding is generally significantly greater than that of the plenum style induction manifolds; but obviously isn't as constant, with reversals that often spike the pressure through the venturi's above atmospheric, again to sums far greater than that of the latter.

    But I suppose, if one were to average these values over a duration of time, then perhaps the meaning in your statement might prove more relevant.  As if the same engine produces approximately the same H.P., even with two different induction systems, then the total air flow sums here, in general, are considered pretty much a constant. But in the instance of the I.R. induction system, with the lack of a plenum effect and volume, this sum of atmosphere volume must pass through the venturi in less time.   

    Scott.

Scott,
My information as to depression differences based on a plenum intake manifold vs. an IR intake came from Dick Carr as a rule of thumb. Dick was a representative of Holley carburetors and one of the Unlimited Class Air Racing Tech inspectors when we were racing the Bearcat for a while. Dick was with Holley when the 4600 series of the really big Dominator was being developed. He offered me a pair of them when Holley gave up on them, but like Holley I couldn't imagine what to do with them either.....



John

[shelbydoug]

This video about flow testing a Shelby COBRA intake manifold although modified with porting may be of interest to some.

https://youtu.be/wZ-ZW2J3Occ?si=9A5TqrRl_Mb-qUj9

Nice. Thank you. I want to see the heads though? GT40's? I can't believe those could be stock iron 289 heads, even ported ones? Not with those numbers?

I'm a bit surprised at the stock out of the box COBRA single four with 240 runners, being that good but HP results of 425-475 ish is what I've seen in actuality with a single 4 no matter what carb was picked. Kiwi's dynoed at 425hp with 331 cubes. I don't recall at what rpm but maybe around 6,600 rpm?


At some point someone will discover the C60A numbers but I'd predict a 500+ hp with it. Maybe even 550? It seems kind of obvious that it has better runner layout for more equal flow balance?

There is a LITTLE bit of the high low runner issue in the plenums with it also like the single 4 COBRA intakes so that can't be eliminated unless you go to a straight tunnel ram or someone from the science fiction group can create a zenomorph intake that varies itself in form and shape as the situation demands. After all, the C60A is a hybrid. A bit of a platypus with characteristics of more then one species.
And how the "balance tube" varies from engine application to application has not been touched upon except to say that the "Windsor" configuration does not work on the "Boss heads" as a direct transplant. That is why I asked in a previous post about that.

Thin castings is something touched upon in the video and something that I am aware of in both the intakes and the heads themselves. The C60A looks even thinner then the COBRA and the only thing that might be possible on it would be an extrude hone but who would want to risk that?


Where Cobra Automotive is getting 620hp is a bit of a mystery to me but a nice number to dream about? With 292ci you probably have to turn it 8,000? 500hp would be a very nice but huge number in the day especially considering that published numbers from the Shelby engine shop claimed 366hp. Now 500 to 620 is quite a discrepancy.  Have alchemists switched from turning lead into gold to engine building?


It's amazing what you (me) can learn if asking the right questions and a key indicator is that I am irritating those in the know enough to the point that they can only hold their tongue for so long without bursting and posting a reply of corrections with what they know? Realize that these are leading questions by me and with statements to encourage that.

All very interesting gentlemen. Carry on please.