The stock threaded side of my emissions tube is much smaller than the thread on pacesetter header emissions inlet. On top of the header. I checked the box but didnt see a replacement part. I put the headers on but the stock emissions tube cant thread into the header because the stock size is to small. They are pacesetter mid length tubes going on a 1995 LT1 camaro. Thanks

 

You mean the air pump fittings with the check valves? They are probably a pipe thread. Not sure why all those header manufacturers put pipe threads on thinking they would work with the air pump check valve assemblies. This is usually the point that one says f it and puts pipe plugs in there and gets rid of the air pump. On the other hand, you can always get a 1/2' pipe plug and drill it out and thread the hole to fit your emissions tubes, and live happily ever after, but all that does is help your cat fire a little earlier - a noble cause no doubt - but damn your car is almost 20 years old and you are modifying it. Up to you how to fix that.

 

Thanks for the reply Kevin. I cant believe this is happening, they go through all the trouble of getting these headers to fit yet don't match the thread to the stock thread. I did tons of home work and reading but never came across this issue.

Fred

 

There are two different AIR pipe thread diameters - a 22mm diameter on the 94/95 single cat manifolds, and a smaller (18mm?) thread on the 95-97 dual-cat manifolds. In 95 the 49-state A4 cars had single-cat manifolds, and the "California emissions" A4 cars had dual-cat manifolds. All M6 cars had 50-state single-cat manifolds. That may be part of the confusion on your 95.

You may be able to find a thread conversion bushing.