Pipe plug size for exhaust manifolds on 305

[ilduce]

1986 305 LG4

Found out today I have no cat; explains why my AIR/SMOG pump has a giant hose going nowhere. So now I get real dual exhaust next week, what a bonus Friday!

I'm considering taking out the AIR pump and its devices. When/if I get those brass/copper line things off the manifolds, what exact size plug do I need to replace them with? I don't want any exhaust leaks coming out of a manifold. It's not something I need to do, but it sure would make it easier to replace crap like the spark plugs.

I saw (but also saw it disputed) through Googling that NPT 1/4 thread pipe plugs will do the trick. Is that true? What length would I need to buy, or are plugs standard length? I've never even bought a pipe plug before, so other than figuring out how to righty tighty them on there, I'm clueless.

 

[mkiiisupra]

I did this to the old 86 Buick Regal I had. Those are the correct size and the ones I bought had a recessed hex head and were approximately 5/8" in length. You can pick them up at any hardware store.

 

[torjan]

better think on getting some cheap shorty headers
and forget the cast stock manifolds

 

[ilduce]

I did this to the old 86 Buick Regal I had. Those are the correct size and the ones I bought had a recessed hex head and were approximately 5/8" in length. You can pick them up at any hardware store.

So I should get NPT 1/4 inch thread pipe plugs 5/8 inches long? Any idea the easiest way to get em?

better think on getting some cheap shorty headers
and forget the cast stock manifolds

I'm not souping it up, so headers are out of the question. It would be nice to get the manifolds from a 305 HO engine but even that's too much $$ to spend on this thing. Then there's how much I'd have to pay a shop to install them, etc. It would be nice though if I could do it for free.

 

[87montecarlomrc]

305 manifolds Aren't any better headers wood be the best thing but since u are just not worried bout power then manifolds will work just fine. I got my hole exhaust done with 2 1/2 pipe and to flowmasters dumped than axle for 135 so it wasn't to expensive really

 

[ilduce]

Will I need to use a locking compound for the plugs?

 

[87montecarlomrc]

Yea it couldn't hurt to use some