Carburetor Question

[rbarkley]

Hey Guys.

I am running a 67 date 427 Side Oiler - MR in my 67 Shelby GT500.   The carburetors are date matched C5AF-9510-BD/BC.  The primary carburetor has a provision for a choke plate, but does not have one installed.  The BC does not have one and is correct from the factory.

Is there an application (67 R code Fairlane or Cobra)  that did not use a choke plate on the primary or has this carb been modified?   What about the primary for the Shelby application BJ/BK. Does it have a choke plate?

Sending the carbs out for complete rebuild and want to know if I should have the choke plate added?

Thanks

Ron

[Royce Peterson]

I've owned several sets of those BC / BD carburetors. The primary carburetors always came with a choke. 

Hey Guys.

I am running a 67 date 427 Side Oiler - MR in my 67 Shelby GT500.   The carburetors are date matched C5AF-9510-BD/BC.  The primary carburetor has a provision for a choke plate, but does not have one installed.  The BC does not have one and is correct from the factory.

Is there an application (67 R code Fairlane or Cobra)  that did not use a choke plate on the primary or has this carb been modified?   What about the primary for the Shelby application BJ/BK. Does it have a choke plate?

Sending the carbs out for complete rebuild and want to know if I should have the choke plate added?

Thanks

Ron

[Bob Gaines]

FYI some of the BC BD have reported on very early 67 GT500's from the factory.

[Greg]

R code Fairlanes had the choke plate from the factory.

[shelbydoug]

The primary carb should have a choke. Mine does.

The only thing with those carbs is I can't get them to idle under 1,100 rpm and can't find the problem.

Drew thinks they will idle higher also but his experience is about 1,000.

[Greg]

The primary carb should have a choke. Mine does.

The only thing with those carbs is I can't get them to idle under 1,100 rpm and can't find the problem.

Drew thinks they will idle higher also but his experience is about 1,000.

My Fairlane is about 1000...  https://www.youtube.com/watch?v=O9RM0hGdks4

[Royce Peterson]

They are very docile carburetors. Remember they came stock on 427 Fairlanes and Comets. Must be something wrong with yours. Plenty of them were fiddled with by people over the last 50+ years not all of the fiddling was knowledge based. I ran a pair of BC- BD's on a stroked 427 and it idled around 650 RPM in gear with the headlights on. Maybe you have a big vacuum leak?

The primary carb should have a choke. Mine does.

The only thing with those carbs is I can't get them to idle under 1,100 rpm and can't find the problem.

Drew thinks they will idle higher also but his experience is about 1,000.

[shelbydoug]

Still looking for the issue. The 1850's idle down to about 750.

Good to know you had them idling down. 650 would be nice.

[Bill Collins]

We had this problem a few years ago and my very astute mechanic traced it to the throttle plates not being properly seated into the bores when the carbs were rebuilt/restored. This prohibited them from fully closing, causing increased idle speed.

He later found the same condition in a friend's GT500. Loosening the throttle shaft screws and manipulating the plates solved the problem in both cases.

[shelbydoug]

We had this problem a few years ago and my very astute mechanic traced it to the throttle plates not being properly seated into the bores when the carbs were rebuilt/restored. This prohibited them from fully closing, causing increased idle speed.

He later found the same condition in a friend's GT500. Loosening the throttle shaft screws and manipulating the plates solved the problem in both cases.

TY Bill. I thought I had looked at that already but considering the symptoms the degree of likeliness is rising rapidly.

[Drew Pojedinec]

Bill is correct, all about closed throttle airflow. Often takes a long time to get them juuust right.
You were mentioning them on a 289, is why I thought you might not get them to idle low enough (I might have been confused on that)

[shelbydoug]

Bill is correct, all about closed throttle airflow. Often takes a long time to get them juuust right.
You were mentioning them on a 289, is why I thought you might not get them to idle low enough (I might have been confused on that)

Not a 289. A 347 with a C60A T/A manifold.

The plan A, is working on the throttle plates for today. The idle circuit on the 4180's went away again and an executive decision has been made by me to release them to boat anchor usage. I'm not going to waste more time on them. A dozen times into them is too much. 

If I can get the 3300/3301 to idle down to 850 or so I'll be happy. Granted, info on my application isn't a snap to find but then again, I always did create my own problems? 

Why take the easy route, anyone can do that? What else would I do, read a book?


I just needed a little encouragement to continue on the BC/BD's, which you all gave me, so thank you all for that.

I'm not sure when stubborn clearly changes over to stupid?  I'm sure, "I'll be the last to know"?


Hey I fixed the Webers. A five pound "lumping hammer" was all that was needed! You just hit them a little here and a little there. 

[rbarkley]

That is what I like about this forum.  In 50+ years there is not much on these cars that has not been repaired, replaced, reworked, rerouted or beat into submission!
I drove the car for about 100 miles the last two weeks and the performance of the motor and carbs were incredible.   My first big block experience and man was it fun!

I knew that the carbs needed attention so gladly dropped them off yesterday for rebuild.  Can't wait to get them back on.

Thanks for all your input.

Ron

[Royce Peterson]

I have had Holley carburetors where the engine would not idle down caused by excessive wear on the throttle shafts and throttle body. In most cases you can find a complete new baseplate / with shafts and butterflies etc brand new from Holley. Others can be repaired by making bushings for the plate and using new shafts.

There are so many different things that can cause this sort of problem. Normally you can send the carbs to an experienced rebuilder (Joe Bunetic for example) and they will instantly spot the problem and will fix it as part of normal rebuild procedures.

We had this problem a few years ago and my very astute mechanic traced it to the throttle plates not being properly seated into the bores when the carbs were rebuilt/restored. This prohibited them from fully closing, causing increased idle speed.

He later found the same condition in a friend's GT500. Loosening the throttle shaft screws and manipulating the plates solved the problem in both cases.

TY Bill. I thought I had looked at that already but considering the symptoms the degree of likeliness is rising rapidly.

[shelbydoug]

I have had Holley carburetors where the engine would not idle down caused by excessive wear on the throttle shafts and throttle body. In most cases you can find a complete new baseplate / with shafts and butterflies etc brand new from Holley. Others can be repaired by making bushings for the plate and using new shafts.

There are so many different things that can cause this sort of problem. Normally you can send the carbs to an experienced rebuilder (Joe Bunetic for example) and they will instantly spot the problem and will fix it as part of normal rebuild procedures.

We had this problem a few years ago and my very astute mechanic traced it to the throttle plates not being properly seated into the bores when the carbs were rebuilt/restored. This prohibited them from fully closing, causing increased idle speed.

He later found the same condition in a friend's GT500. Loosening the throttle shaft screws and manipulating the plates solved the problem in both cases.

TY Bill. I thought I had looked at that already but considering the symptoms the degree of likeliness is rising rapidly.

A point well taken.

These came out of the Holley Custom Shop. Drew can tell you how many of those he needed to finagle with.

I'll save him the time, he's not surprised and this is typical. The re-dying came out nice though.


Drew is very busy. Right now you need to wait until the fall to get him to look at them.

You are also taking the chance that he comes back after the 42 day hitch and his tug boat is not torpedoed by anarchists in the Gulf? These days, there's no guaranties! Someone can take you out just running down to the corner store.


See. This is why the cowboy movies were good. The good guys wear the white hats, the bad guys the black hats.