Exhaust Manifold Plug?

stwilegar

stwilegar

Member
1972 Scout ii, 345, 727.

Hey all. I'm doing a bit of exhaust work and after repairing some piping realized there is a missing a plug that is situated on the topside of the passenger exhaust manifold. It's about 3/4" threaded hole. Ibcould go to the hardware store to get a generic plug but I'd still like to know the purpose of this hole. I'm assuming some of yiu old timers might know.
TIA
Bridger
North Idaho
 
My 74 Scout had the smog pump plumbed into these holes. Should be no problem to plug them. IIRC they are 1/2" NPT.
 
Hello, new here. First time posting. Is this the bolt/plug you’re asking about? I’m missing one as well. Is this part available or can I use a generic bolt? This has a little rubber o-ring at the end of the threads.
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That will work, but your likely to get a chirp at certain engine speeds as the exhaust moves over the empty hole where the shoulder was. Don't they still sell those plugs here?
 
That’s the existing plug in the next cylinder. I can’t find that exact plug. Foimd this on Amazon:
 

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I haven't noticed a chirp but then I haven't been listening for one. The Brass plug fits snug and goes into the manifold a good amount. I'll pay attention and see if I can identify a chirp.
 
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