Vintage Ford Intake Manifold CFM flow numbers

[Zelda]

Hi! Finding CFM flow data for '60s intakes is tough. Cobra Automotive did offer Extrude Hone on high-rise intakes, so reaching out to them might help. As for published results, most seem to come from individual testing, like dyno runs—specific publications are rare.

Adding: Try checking Mustang or Shelby forums—folks there sometimes share custom test results. Extrude Hone really improves flow consistency, so it's worth exploring. Let us know if you find anything! 😊

[FL SAAC Team Leader]

Hi! Finding CFM flow data for '60s intakes is tough. Cobra Automotive did offer Extrude Hone on high-rise intakes, so reaching out to them might help. As for published results, most seem to come from individual testing, like dyno runs—specific publications are rare.

Adding: Try checking Mustang or Shelby forums—folks there sometimes share custom test results. Extrude Hone really improves flow consistency, so it's worth exploring. Let us know if you find anything! 

Zelda
Big plus one

[shelbydoug]

The lac

Hi! Finding CFM flow data for '60s intakes is tough. Cobra Automotive did offer Extrude Hone on high-rise intakes, so reaching out to them might help. As for published results, most seem to come from individual testing, like dyno runs—specific publications are rare.

Adding: Try checking Mustang or Shelby forums—folks there sometimes share custom test results. Extrude Hone really improves flow consistency, so it's worth exploring. Let us know if you find anything! 

The lack of any response from them was a key motivator to initiating this post to begin with.

If and when I get any response I intend to share but don't feel encouraged so far.

[pbf777]

     In my observations, the "Extrude-Hone" process and resultant effect, as generally practiced, presents little more than a surface smoothing result; handy for manifolding that is of greater lengths and complexity than true hand or CNC porting would permit for, but not effectively capable of all of that which one generally expects from a properly ported for best performance manifold example. 

     In my opinion, the best application of the extrude-hone process would be as a final treatment, this 'after' conventional porting work had been done where selective material arrangements are made and afterward all is then "polished-up". 

     Scott.

     

[pbf777]

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.

      A couple of dozen and more years ago we were building "truly legal" F.I.A. 289's that 'were' durable and clearing 450+ H.P..  But today there has been a significant increase in the availability of specialty "replacement" parts and rule adjustments that are permitting greater sums of power; not to mention, it seems no one is actually building "truly" legal examples, or at least not anything that would represent a "truly vintage" example these days! 

      This is not to say that all of the numbers being toss around are accurate; but then, when in history did anyone actually believe any of the horsepower numbers ever having been bantered around as being accurate and not having been "adjusted" for one reason or another?   

      Scott.

[shelbydoug]

Your point is well taken by me.

The only reason I even brought up the subject was the mentioning of it in a discussion with Cobra Automotive.
In it, it was mentioned that with the Blue Thunder version, on their flow bench, the before and after was a plus 10%.

So if that is in fact accurate and not just bluster, the suggestion is that the Blue Thunder went from an average runner flow of 240cfh to 264cfm. That is a nice increase but I'm not sure if I would consider it economical at $750 for the process? Now that wasn't part of my initial question and rather then the COBRA single 4v, I was more interested in the various flow numbers on the T/A versions.

Those runners volumes are more generous in cross sectional area already, shorter and more direct in WOT mode. So first of all, the only base number that I have is what Randy thought they would be as cast at right around 240cfm, which is what he had documentation on for the iron GT40 heads.

Extrude hone on a C60A may just be more effective on the T/A's simply because of the differences in the runner designs? All speculation on my part but it is pretty cold and snowy here now so what better things do I need to do to keep busy?

[shelbydoug]

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.

      A couple of dozen and more years ago we were building "truly legal" F.I.A. 289's that 'were' durable and clearing 450+ H.P..  But today there has been a significant increase in the availability of specialty "replacement" parts and rule adjustments that are permitting greater sums of power; not to mention, it seems no one is actually building "truly" legal examples, or at least not anything that would represent a "truly vintage" example these days! 

      This is not to say that all of the numbers being toss around are accurate; but then, when in history did anyone actually believe any of the horsepower numbers ever having been bantered around as being accurate and not having been "adjusted" for one reason or another?   

      Scott.

620hp is a big claim. A "True Grit" one in fact. And just like in "True Grit", "it's mighty big talk for a one eyed fat man!" 


So really if I consider the adage of hp = 2 x air flow, at 450 and 240 your resulting numbers tend to agree.

To get to 620 the air flow should be more like 300cfm? As I said, "mighty big talk".

I'm not blind and fat enough YET to make those kind of claims.


I did see the #1 C/A car run until it blew the engine in practice. Then saw the back up car and there was a big difference.
Whereas the #1 was leading the pack, the backup had difficulty keeping up. There was more then witchcraft involved in that. I don't get involved in that. I already have enough curses cast on me. I don't need more.

[pbf777]

............ it was mentioned................., on their flow bench, the before and after was a plus 10%.

So if that is in fact accurate and not just bluster,.............. That is a nice increase but I'm not sure if I would consider it economical at $750 for the process?

      Well, if one wants to be competitive, porting work is a requirement! 

      And as one whom has been in the business of executing porting work in the past, a 10% port flow increase is an aggressive, but not necessarily unreasonable expectation (here); that with the proper effort put forth.  But stop, and think about the time element involved in accomplishing this?  And at $750., I can't pay a guy to sweep the floors for the resultant hourly rate that would be commensurate with the number of hours I'd have invested in accomplishing this task properly!   

      So, what are you actually getting, for what is actually a pittance of a charge, for the effort (supposedly) being put forth?   

      Scott.

[shelbydoug]

............ it was mentioned................., on their flow bench, the before and after was a plus 10%.

So if that is in fact accurate and not just bluster,.............. That is a nice increase but I'm not sure if I would consider it economical at $750 for the process?

      Well, if one wants to be competitive, porting work is a requirement! 

      And as one whom has been in the business of executing porting work in the past, a 10% port flow increase is an aggressive, but not necessarily unreasonable expectation (here); that with the proper effort put forth.  But stop, and think about the time element involved in accomplishing this?  And at $750., I can't pay a guy to sweep the floors for the resultant hourly rate that would be commensurate with the number of hours I'd have invested in accomplishing this task properly! 

      So, what are you actually getting, for what is actually a pittance of a charge, for the effort (supposedly) being put forth? 

      Scott.

That was the original selling point of the extrude hone. I have done a bit of porting myself.

The last set of heads that I did sold for $500 with new bigger valves, a couple of days or more worth of grinding plus the customary competition valve job.
Ultimately the selling price was just to move them out of the way since they were old news and I had moved on.

Thinking of people like Kaase, in order for him to be competitive in these engine building competitions, he can't even pay himself I'm very sure.

It is the nature of the beast even if you now have a CNC robot?


I've already acknowledged that much of this development work was done initially in the mid '60s and likely the payday back then per man was in the $150 a week area, even though being funded (in this case) by Ford. It kind of easily justifies buying aftermarket cnc'd heads even if the advertised flow numbers are over stated some. They are done as they come in the door and you can just bolt them on.



I am largely agreeing with you on all written but this really is all academic at the moment? Since I am hearing crickets on my intake inquiries, not numbers so far? But just base numbers, tested as cast, even old ones would help in explaining even old approaches and maybe emphasize how lucky we are now to get even old tech, high performance items for less then what dirt costs now? But I already have realize how fortunate I have been in even having owned some of this "King of the Hill" stuff even momentarily.

Even carburetors are to the point of being museum pieces.


Here's an artists drawing of me as a boy walking my dinosaur. It was a Tyrannosaurus Rex. Even then I had the biggest and meanest. It is actually a photo of the art which was done on the wall of the cave where I was brought up in. It isn't black chalk. It is a cooled burnt piece of charcoal wood from the fire place. Cameras and art supplies didn't exist then yet.

[JohnSlack]

Doug,
Ford learned a whole bunch between the C6OA-A intake and the stillborn no part number BOSS 302 intake manifolds, I put them on the bench together for the first time. As I'm doing work on the C6OA-A intake manifold I took my Depstech camera and wandered through the ports, including the balance tubes. The balance tubes are well finished in typical casting finish. I would describe them as generous in proportion. I think I have to disagree with you on the "equal length" I can see similar length for #s 1,5,7 & 3, with much short and more direct lengths on #s 2,4,6,& 8. However I can agree with you on that Randy Gillis put me on to both of these intake manifolds (The C6OA-A and BOSS 302 T/A Std. Flange dual plane 2x4 intake) as the best in class by far for each head configuration. The Ports in the BOSS 302 intake manifold and the balance tube area are of course "cavernous" in proportion to the C6OA-A intake. And the BOSS 302 intake is actually pretty darn close to equal lengths in the runners. The down side of that is the need for additional rare hardware in the offset distributor.


I'd also love to get flow numbers on the intake manifolds, but I'm guessing that with all of the balance passages the only real answer is to meter the air going through the engine actually on a dynamometer. Which adds more questions than answers... correct?

Glad to see you had a T-Rex as a child, however all of our FE friends laugh at us when we consider any small block a beast... probably for good measure, eh.


John

[68countrysedan]

Filed under if anyone knows:

Did NASCAR teams (then or now) do manifold flow testing, not that they would reveal what they found, but details might have eventually leaked.

In discussing manifold flow, does reverison into the runner when the intake opens have any flow impact or is it too small to notice.

per Zora Arkus-Duntov: ". . .one man's thinking aloud on the subject."

[shelbydoug]

Doug,
Ford learned a whole bunch between the C6OA-A intake and the stillborn no part number BOSS 302 intake manifolds, I put them on the bench together for the first time. As I'm doing work on the C6OA-A intake manifold I took my Depstech camera and wandered through the ports, including the balance tubes. The balance tubes are well finished in typical casting finish. I would describe them as generous in proportion. I think I have to disagree with you on the "equal length" I can see similar length for #s 1,5,7 & 3, with much short and more direct lengths on #s 2,4,6,& 8. However I can agree with you on that Randy Gillis put me on to both of these intake manifolds (The C6OA-A and BOSS 302 T/A Std. Flange dual plane 2x4 intake) as the best in class by far for each head configuration. The Ports in the BOSS 302 intake manifold and the balance tube area are of course "cavernous" in proportion to the C6OA-A intake. And the BOSS 302 intake is actually pretty darn close to equal lengths in the runners. The down side of that is the need for additional rare hardware in the offset distributor.


I'd also love to get flow numbers on the intake manifolds, but I'm guessing that with all of the balance passages the only real answer is to meter the air going through the engine actually on a dynamometer. Which adds more questions than answers... correct?

Glad to see you had a T-Rex as a child, however all of our FE friends laugh at us when we consider any small block a beast... probably for good measure, eh.


John

Actually it was a "family T-rex". My Father would tell me to take him for a walk after my Mother would yell," I'm not cleaning that up!".
It was actually the saber tooth tiger that was the problem. He would spray everything to mark his territory which included my personal possessions as well! Yuck. It stunk!

I'm not immune to big blocks. There doesn't seem to be much science involved in them though? My 67 GT500, you just kind of point and hang on and it just goes where it wants to.

It is kind of like Hulk Hogan, both in appearance and performance. Not much intelligence going on there at all? Like a Defensive nose tackle. I'm more of the "fake you out quarterback type". Often causing problems because I thought I was smarter then the defense? It is humbling to be out thought by a bunch of Neanderthals.


I actually took a cloth tape measure that I borrowed from my wife's sewing box and measured the length of the runners
internally on the C60A. That was enough evidence for me to call them equal length. That tape measure does not stretch at all. They are within an inch of each other along the top of the ports where the snug tape would sit.

Remember, you will never know with me if I made a misstatement about something intentionally or just unknowingly. I find I get more response from those because others need to correct me with the actual data.
Kind of like how Scarecrow gets the apple trees to throw apples at him.


The B2 version is really very curious. It would be very interesting to combine them with the "recent" C302 heads to see if they like each other?

Interesting that it would seem that the significant difference between that one and the Shelby script B2 version is the carb positioning. I do remember Randy saying that but I thought he was talking about the rear carb, not the front? He was talking about the rear carb secondaries hanging out the back too far to be useful, on the Shelby script intake. He never mentioned the front carb positioning as I recall?


On my C60A, I thought that I had noticed a closing down of the balance tube into the front plenum by around 50%,  which is why I am curious about variations like if the C60E is different? Maybe mine needs an angioplasty on the balance tube?


Do you have any of those Ford "Cleveland" aluminum heads out of the "Indy Program"? The ones with the cast in radical high port exhausts like Nicholson wound up with on the iron Pro-Stock heads?

Randy said he bought out Nicholson's stuff at some point. Mentioned the aluminum blocks but don't remember him mentioning the heads?


On the extrude hone, my thought initially was that was essentially just an internal polishing of the runners but in thinking about head porting, mostly, that is also. As Scott pointed out, a 10% increase is a nice number considering the alternative procedures available at a much greater expense?

[pbf777]

Did NASCAR teams [THEN] do manifold flow testing, not that they would reveal what they found, but details might have eventually leaked.

    I'd have to say that beyond the manufactures initial design stage of development where establishment of manifold function was being considered, the rest probably fell under the statement of:

author=JohnSlack link=msg=209911 date=1737434301]
I'd also love to get flow numbers on the intake manifolds, but I'm guessing ............. the only real answer is to meter the air going through the engine actually on a dynamometer.

     Or, just the resultant performance on the track! 

     Next:

In discussing manifold flow, does reversion into the runner when the intake opens have any flow impact or is it too small to notice.

    This issue does not appear in the typical flow-bench testing process, but has come to light to those whom start to consider the fact that:

the only real answer is ................................... actually on a dynamometer. Which [often] adds more questions than answers... correct?

    Correct!     

    Scott.

[shelbydoug]

When I went in this direction of the C60A the "feasibility study" that I did was that for a 8.2" Ford small block engine of the era, that I wanted to look at least period correct, that intake was pretty much the best that I was going find.

Everything else it provided, if anything, was just a bonus.

[pbf777]

    Also, I think here we're getting to enthralled with the existence and possible effects of the "balance-tube", as we're not truly designing or redesigning an intake manifold from scratch; simply consider it as the established necessary concession for better carburetor function and fuel distribution not really having any great effect on flow-bench testing.   

    And considering the dynamics, this probably is one of those things that are better "tested" in actual function, rather than on a bench or on paper.   

    Scott.