I'm removing my air tubes and all the emission stuff. What size nut should i use to close the holes up in the manifolds after i take off the air tubes? what size bolt and threads are they?

I don't see how you could use a nut to close up the hole. But, anyway, just go to a hardware store (you know Lowes, Home Depot) and get eight 1/4" pipe plugs. That should do it. I am using those on my exhaust manifolds and they haven't leaked yet. Don't forget to use some teflon sealant on them, too, so they really won't leak. I forgot to use some but I wouldn't recommend not using some.

sorry for my lack of knowledge but what's a pipe plug. What's the difference between a nut and a pipe plug?

Oh, no problem.

A nut has threads on the inside of it. You put a nut on a bolt, not in place of it.

A pipe plug is just this piece of brass with threads on the outside of it. It looks like a bolt but it doesn't have a six-point head on it. Instead it has a square head on it (you have to use a wrench to get them on since they're square).

If you go to a hardware store and just ask them, they should tell you where they are and what they look like. They should be in either the plumbing section or the nut and bolt section.

Wow, I'm just dumb, long sleepy day. I ment bolt, not nut. I understand now the confusion. Sorry about that. I'll pick the pipe plugs up asap. thanks

Hey, don't worry about it. Everyone says and does stupid stuff all the time, especially including me. You wouldn't believe some of the stuff I've tried to do/modify/fix my car.

Actually the fittings aren't 1/4 pipe, they're tube nuts. Go to a good autoparts store and they'll have them in a bin. The right hardware is cheap enough that there is no reason to use the wrong hardware. Also the manifolds have flared seats, a pipe plug will damage the manifolds and probably won't seal either.