SLIMJIM

I am installing some headers on my '95 Z28 and have a question about the A.I.R. fitting. What size are the threads on this thing? The fitting is too small for the new headers.



Thanks for the help.

Injuneer

The single-cat exhaust manifolds used a large thread that was roughly equivalent to an M22-1.5 oil drain plug. The dual-cat (CA Emissions A4's) manifold used a smaller thread that was closer to an M18. That's what people use to plug the holes. Sounds like the holes in your headers must be the larger M22's. Are the holes in the headers about 7/8" in diameter?

SLIMJIM

Yes they are almost exactly 7/8".
My car has the single cat exhaust. The headers are Pacesetter mids 70-1335, if that helps. I emailed them, but I haven't heard back from them yet.

SLIMJIM

Yes, I do. No they won't.

I'll have to do that tomorrow, maybe I'll get lucky.

canuck94z28

Me and my buddy went on EBAY and ordered 2 sets from a guy in Arizona and they were m22 x 1.5 .Cost was 9.95 ea.and i also used a small copper plug and sealer and the plugs fit fine,i could not find anything locally

Injuneer

There's a place in Canada sells the M22 oil drain plugs for less than $2 each. They are also available from Dodge dealers, since the Cummins Diesel used in the Dodge trucks has an M22 drain plug. But he's saying the STOCK pieces will not thread into the Pacesetter headers either, so that would sort of rule out M22's.

http://www.cgenterprises.com/drain_plugs_metric.htm

SLIMJIM

Well, one step closer anyway.
To my surprise, the non-flared end isn't metric but is 3/4"-16 machine thread. The flared end is not a big deal, yet. I think it's just a standard flare fitting anyway.

SLIMJIM

As a matter of fact those fittings ended up being 7/8"-18 machine thread.

pcgamer4life

Like Injuneer said, M22 oil drain plug will work perfectly. You can get them at any auto parts store for a newer model dodge diesel for a couple of bucks a piece.

SLIMJIM

Well, after doing some more research, I found the answer to my problem. I ended up having to get the AIR tubes off of a 1994 LT1 to fit the headers. Evidently GM changed the fittings in mid '95 to a newer design more like the '96-'97 LT1's .


This one fits much better.

Thanks for all the help.

I'll post pictures of the install when I get everything going.

Tobyvanhorn

I know this is old but I am having the same issue and had a question - is the thread 3/4 x 16 or 7/8 pipe thread or are they the same? I may need to cust and add a fitting to redo smog tubes

Injuneer

I swapped out the stock manifolds on my 1994 for a set of AS&M single cat mid-lengths. Took the stock AIR fittings off the stock 94 manifolds, and they fit perfectly into the AS&M headers. Eventually I deleted AIR, bought two M22-1.5 oil drain plugs, plus matching copper washers, and the oil drain plugs also fit perfectly into the AS&M headers. They are straight threads, not tapered pipe threads.

Appeared to be correct for 1993-1995 headers, with one exception. In 1995 the California emissions A4 cars had dual cats, and apparently used the smaller fitting used in the 96-97 dual cat manifolds. The oddball 95 CA emissions, and 96-97 cars may be 3/4-16, but I have not personally verified that because I haven’t worked on the AIR fittings of those cars.

Another caution - not all header manufacturers used the GM specs. There was one outfit - can’t remember which one, it was 20+ years ago - that had an external thread on their header AIR pipes, and required some sort of adapter to hook up stock AIR fittings.

Tobyvanhorn

Thanks for the info - got some plugs to fit headers are 3/4” - I have yet to get my tubes off but the oem size seems to be 7/8 everywhere I look pacesetter says that an adapter may be needed.

I was considering cutting as low as I can and have a shop out the 3/4” nut at the bottom and run without an adapter?

anybody have examples of putting smog tubes on pacesetter 70-1335?

Injuneer

Would make sense for a header manufacturer to supply the headers only with the larger diameter AIR connections, because they can accommodate the smaller diameter connection with a bushing. Keeps them from having to build two different headers for 4th Gens. As far as the larger fitting, I've seen people call it 7/8" (0.875") and that is what someone might approximately measure if they are looking at a 22mm fitting (0.866").