1972 Corvette Carb to Intake seal - Just cannot get rid of this last vacuum leak!!

[Christopher R.]

any ideas as to how to get a good seal from the carb to the intake manifold? I have tried new gaskets, torquing the bolts in the proper sequence and i still have a leak on the passenger side right next to where the choke assembly is, this is obviously causing me drivability issues and issues with the vacuum operated items like the wiper door and headlights.

[Mark E.]

Re: 1972 Corvette Carb to Intake seal - Just cannot get rid of this last vacuum leak!

How did you confirm there's a leak and its location?

And the brand and PN of the gasket tried?

[Christopher R.]

Re: 1972 Corvette Carb to Intake seal - Just cannot get rid of this last vacuum leak!

i can hear it literally breathing through there, almost like an exhaust leak sound. i put on the stethoscope and can clearly hear it leaking

[Mark E.]

Re: 1972 Corvette Carb to Intake seal - Just cannot get rid of this last vacuum leak!

i can hear it literally breathing through there, almost like an exhaust leak sound. i put on the stethoscope and can clearly hear it leaking

Gasket used?

Original/replacement style Q-Jet and manifold? Or a modified set- up?

[Patrick H.]

Re: 1972 Corvette Carb to Intake seal - Just cannot get rid of this last vacuum leak!

How about a picture of the gasket you're using?

[Carl N.]

Re: 1972 Corvette Carb to Intake seal - Just cannot get rid of this last vacuum leak!

Maybe carb base is warped, rare but possible.

[Joe L.]

Re: 1972 Corvette Carb to Intake seal - Just cannot get rid of this last vacuum leak!

any ideas as to how to get a good seal from the carb to the intake manifold? I have tried new gaskets, torquing the bolts in the proper sequence and i still have a leak on the passenger side right next to where the choke assembly is, this is obviously causing me drivability issues and issues with the vacuum operated items like the wiper door and headlights.

christopher-------

If the proper gasket won't seal it, then the problem has to involve some warpage of the carb throttle body or the manifold's carb flange. I've never seen warpage of a manifold carb flange be a problem, though. Another possibility is that the leak is not actually emanating from the carb-to-manifold interface and is, instead, due to wear in the throttle shaft bores in the throttle body (a common problem).

By the way, the correct gasket is a thick insulating gasket. You can still get its "direct descendant" from GM under GM #10069984, aka Delco #216-82.

[Leif A.]

Re: 1972 Corvette Carb to Intake seal - Just cannot get rid of this last vacuum leak!

Maybe carb base is warped, rare but possible.

Carl,
I would not think rare at all, but quite possible. Get some gorilla armed mechanic cranking down on those four nuts and warpage is inevitable.

[Mark E.]

Re: 1972 Corvette Carb to Intake seal - Just cannot get rid of this last vacuum leak!

Carl,
I would not think rare at all, but quite possible. Get some gorilla armed mechanic cranking down on those for nuts and warpage is inevitable.

On a Q-Jet, over tightening the four hold down bolts/nuts can bend or crack the air horn or maybe fuel bowl. The throttle body usually survives.

But there still isn't enough information from the OP to diagnose his specific problem.

[Christopher R.]

Re: 1972 Corvette Carb to Intake seal - Just cannot get rid of this last vacuum leak!

the carb was sent out to a reputable builder and it works quite well. I am using the thick insulating gasket that all of the corvette vendors are selling. i have the stock manifold and i ran a straight edge across it and could not see any signs of it being warped. if the carb base is warped, then it will have to go back out again. Thanks for all of the suggestions. My vette is bone stock and i tried to bring everything back to exactly the way it was in 1972, I will send it back out over the winter - perhaps in the interim I will just get a edelbrock carb !

[Patrick H.]

Re: 1972 Corvette Carb to Intake seal - Just cannot get rid of this last vacuum leak!

The current Edelbrock carbs won't work on your manifold, so that is an extensive modification.

A picture of the gasket means a lot more than saying it's the same one everyone sells. I received and installed the wrong one once, so you may have as well.

Then, if you could video the engine and noisy carb....

[Mark E.]

Re: 1972 Corvette Carb to Intake seal - Just cannot get rid of this last vacuum leak!

the carb was sent out to a reputable builder and it works quite well. I am using the thick insulating gasket that all of the corvette vendors are selling.

The carb works quite well? I thought there were drivability issues and a vacuum leak.

I echo Patrick's comment about the gasket. There are a myriad of Q-Jet manifold gaskets for a myriad of applications. Use the wrong one and there are problems.

Joe has a good point about a leak around one of the throttle shafts. Shaft wear is common, which will cause a leak in the area you describe. So make sure the source of the leak is carefully diagnosed. Also, the throttle body to fuel bowl gasket is a fraction of an inch above the manifold gasket, so that is another possibility.

If the leak is definitely from the manifold/throttle body gasket and the correct gasket is used with proper torque, then something's not flat or clean. One trick for more "crush" with the same torque is to install an OE heat shield that came with some of the emissions Q-Jets. This creates a gasket/shield/gasket interface which may compensate for a slightly warped surface.

[Edward M.]

Re: 1972 Corvette Carb to Intake seal - Just cannot get rid of this last vacuum leak!

Get some soapy water (dish detergent soap) in a spray bottle. Spray the area where you think it is leaking. Watch for bubbles. Spray various areas until you find the bubbles. That is your leak.

[Edward J.]

Re: 1972 Corvette Carb to Intake seal - Just cannot get rid of this last vacuum leak!

A little carb. cleaner works better to find a vacuum leak. just spray a small amount in the area you think is leaking and if the RPM's pick up you found your leak.

[Patrick H.]

Re: 1972 Corvette Carb to Intake seal - Just cannot get rid of this last vacuum leak!

The down side to carb cleaner is that it can stain the paint of your intake manifold, if you care.