hubturn

Mine was 8m x 1.25. I know because I snapped the tap thinking I didn't need lube for such a short distance. I was lucky to get the tap out. Cast iron, heated up and hardened - I wasn't thinking! That's for a '95 Cab, AAH engine. I can't imagine the AFC being different, if that is what you have. You do know to put two nuts on the stud and lock them against each other so that you can get a wrench on them to tighten the stud down?

flyingscott

Awesome, thanks for the thread pitch, I thought it was weird that it wasn't listed.

I was just going to clamp some vice grips on the end of the stud and crank down...kidding! I have experienced studs in other applications at work, but thanks for the heads up.

AFC and AAH do share the same exhaust manifold parts and setup.

Did you drill all the way through the flange and thread a through hole or did you stop at the bottom of the stud and use a bottoming tap?

hubturn

Those three flanges on the exhaust manifold are only about 3/8" thick. They are threaded all the way through. If they are so rusted that you can't cut or clean up the correct threads, maybe there is a stud with a larger size on one end. I had one that wasn't perfect, but was still able to hold the new stud. Also, there is no gasket or seal of any type at that joint. Just the taper fit between the two surfaces. Surprised me, too. Back in the day there would have been an asbestos ring in there. I also recommend going to a good ACE hardware and getting a metric thread gauge. You will always need it.

1993audi90

Needless to say, drilling and retapping larger holes means you should use all three taps in proper order. And you should be noting that the hole needs to be at 90 degrees perpendicular from the CL of the flange hole. It would suck to get all new studs in, get it on the car to find out that the flange on the CAT isn't going to fit your new stud pattern because one or more of the studs is off CL. Then you'll have to drill the holes bigger in the CAT flange to make up the distance--and may need to use washers before the Nut if the hole has to be so big the nut will not seat right.
If there is anything at all left of the busted off stud to get vice grips on it, get your torch out heat that bitch red hot, grab the stubby and try turning it out. you save your threads, everything goes back together good and happy, and you can reward yourself with a few beers afterwards.

flyingscott

Picked up two manifolds from the jy today, and got the studs out. The threads are still a little rough, a M8x1.25 bolt I got doesn't like to thread, so I'm going to clean them up with the nice tap I got. So at least I have these if I can't get the studs off the manifolds on the car.

Thanks for all the help so far, I'm going to start this tomorrow. Wish me luck.