intake problem

[Brent M.]

intake problem on bb may have vac leak or heat problem with metal shim under cab

[Joe L.]

Re: intake problem

intake problem on bb may have vac leak or heat problem with metal shim under cab

Brent-----


I'm not sure I understand your question. However, if what you're referring to is some sort of a suspected vacuum leak at the carb base and your engine is an L-36, here's what I recommend you do:

1) Remove the carb from the engine;

2) Thoroughly clean the carb flange on the manifold and check it for flatness using a precision straight edge. If the pad is at all warped, then you must remove the manifold from the engine and have the flange surface machined;

3) Plug the holes on each end of the carb "heat slot on the forward side of the manifold's carb flange. If the manifold is installed on the engine, you can do this using drive plugs of the appropriate size. These are like small freeze plugs and can be obtained at good auto parts stores. If the manifold is off the engine (e.g. due to the above), then i recommend you drill and tap the holes for internal hex head pipe plugs;

4) Reinstall the carburetor using a NEW gasket. Install the gasket first on the manifold, then the stainless steel heat shield on the top of the gasket. Finally, install the carburetor.

All your problems should be over.

[Brent M.]

Re: intake problem

Brent-----


I'm not sure I understand your question. However, if what you're referring to is some sort of a suspected vacuum leak at the carb base and your engine is an L-36, here's what I recommend you do:

1) Remove the carb from the engine;

2) Thoroughly clean the carb flange on the manifold and check it for flatness using a precision straight edge. If the pad is at all warped, then you must remove the manifold from the engine and have the flange surface machined;

3) Plug the holes on each end of the carb "heat slot on the forward side of the manifold's carb flange. If the manifold is installed on the engine, you can do this using drive plugs of the appropriate size. These are like small freeze plugs and can be obtained at good auto parts stores. If the manifold is off the engine (e.g. due to the above), then i recommend you drill and tap the holes for internal hex head pipe plugs;

4) Reinstall the carburetor using a NEW gasket. Install the gasket first on the manifold, then the stainless steel heat shield on the top of the gasket. Finally, install the carburetor.

All your problems should be over.

Thanks Joe
I had a machine shop make me a aluminnum gasket just like the intake
but the heat slot was not cut
The gasket is 1/8" thick
Should I still block the holes on intake?
Joe please feel free to call 225-278-6393 I will pay for the call
Thanks Brent

[Joe L.]

Re: intake problem

Thanks Joe
I had a machine shop make me a aluminnum gasket just like the intake
but the heat slot was not cut
The gasket is 1/8" thick
Should I still block the holes on intake?
Joe please feel free to call 225-278-6393 I will pay for the call
Thanks Brent

Brent------

I would block the heat slot holes on the intake in any event. They are unnecessary and cause mostly harm and little, if any, good. GM dropped them after 1969 from all manifolds.

If you keep the holes I would absolutely not use the aluminum plate in place of the stainless steel baffle. I'd be reluctant to use the aluminum plate anyway. Among other things, in doing so, you're raising the carburetor about 1/8". There is very little air cleaner-to-hood clearance on 68-72 big blocks as it is. I would not want to lose another 1/8" of it. You can purchase a reproduction stainless steel shield from Dr. Rebuild for about 10 bucks. In addition, if you eliminate the heat slot by plugging the holes, you don't even really need the stainless steel baffle.

By the way, if you were to use the aluminum shield you had made, there should NOT be a heat slot cut in it. That would defeat the entire purpose of the shield. The stainless steel baffle had NO heat slot cut in it. However, as I mentioned, the best thing to do is to eliminate the heat slot by plugging the holes. I would absolutely NEVER use a manifold with an active heat slot. Ever.