What is the correct plug for this fitting ?

[Bill K.]

The vacuum fitting on my 400hp motor has a rubber plug, see photo. Anyone know what the "correct" way is to cap this fitting for judging ?

Thanks, Bill

[Richard M.]

Re: What is the correct plug for this fitting ?

This L71 435hp original manifold(different on 400hp), had what appears to be a cupped welch plug.

P4020017.jpgP4020021.jpg

[John H.]

Re: What is the correct plug for this fitting ?

The vacuum fitting on my 400hp motor has a rubber plug, see photo. Anyone know what the "correct" way is to cap this fitting for judging ?

Thanks, Bill

Bill -

As I recall, that lower tube was only present on 400hp intake manifolds with K-19, where it connected a hose to the base of the air cleaner; without K-19, it had a welch plug, as Rich noted (plug or tube were installed in the intake at Tonawanda, not St. Louis).

[Bill K.]

Re: What is the correct plug for this fitting ?

Thanks, I looked at a friends 435 non A/C non K-19 car and I now see what I should have. Can anyone tell me if this is pressed in or screwed in, I don't want to get into something I can't undo ! Can I correct this without removing the manifold from the car ? Where can I find the correct plug. I looked in Paragon and Long Island but can't narrow anything down to the correct plug.

Thanks, Bill

[Joe L.]

Re: What is the correct plug for this fitting ?

Thanks, I looked at a friends 435 non A/C non K-19 car and I now see what I should have. Can anyone tell me if this is pressed in or screwed in, I don't want to get into something I can't undo ! Can I correct this without removing the manifold from the car ? Where can I find the correct plug. I looked in Paragon and Long Island but can't narrow anything down to the correct plug.

Thanks, Bill

Bill-------


The problem here is going to be removing the existing fitting. This will be an interference-fit (i.e. pressed-in) fitting. The easiest way to get it out will probably involve knocking it out from the rear which, of course, would necessitate removing the manifold from the engine.

Welch plugs of the appropriate size will likely be available in most good auto parts stores. The size will be the diameter of the orifice in the manifold. Barring that, if you report on that size, I might be able to tell you if an appropriate welch plug is still available from GM.

[Bill K.]

Re: What is the correct plug for this fitting ?

Thanks Joe, I plan on getting the car judged in the spring. I may take the hit vs all the disassembly work required.