69 L36 intake manifold exhaust passages

[Greg L.]

I see that it is recommended to plug the exhaust passage under the front of the carb so I have two questions.

1) Why is it recommended to plug this passage?

2) What is the common method to plug the passage?

I was also reading a post a few days ago about proper carb/intake gasket stack-up on this engine and I'm currious as to how well this stainless plate seals against the carb? I would tend to think that you would get vacuum leaks to a degree so is there a sealant that should be used or is it really just, manifold-gasket-stainless plate-carb?

Thanks.

Greg Linton
#45455

[Clem Z.]

Re: 69 L36 intake manifold exhaust passages

it is not needed as GM did away with it in later years. cup type expansion plugs from the auto parts are used to plug them with the manifold on the engine. NEVER tap the manifold for threaded plugs on the engine as it will allow metal chips can get into the combustion chambers. when the carb is new the throttle base plate is flat and seals very well to the stainless steel BUT as the carb gets older the base plate get warped, possibly from the excess heat of the open heat passage, and will not seal without a gasket unless you have the base plate machined flat

[Greg L.]

Re: 69 L36 intake manifold exhaust passages

Thanks Clem. My intake is still off of the car so I guess I could tap the holes for screw in plugs if I can't find those tiny press in plugs.

I'll check my carb for warpage too but I'll bet that it will be like most Q-Jets.