Fixing stripped studs on cast iron exhaust manifold?

I received some cast iron manifolds the other day, and the flange that goes to the y-pipe has stripped out studs. The threads are berkeleyed.

NAPA has these exhaust manifold stud kits that are essentially wheel studs... a flanged and splined end with proper threads on the other. Drill the manifold, and press in the studs. My understanding of cast iron is it's brittle and prone to cracking. I don't have access to tap sets, and I am not a fan of through bolts. Are my concerns justified?

For what it's worth, I have access to crappy drill bits and a decent drill press.

What would you all do?

Also, while I'm here, any tips on flattening flanges? These need to be cleaned up.

Helicoil what you have.

Look closer at the existing studs. As I recall, they are threaded in. This means they can be unthreaded. At least in theory. Frequently you drill them out to the edges of the threads, and then use a chase or tap and push the remaining threads out. Then you simply screw in a new stud or bolt.

The threaded holes themselves are stripped.

Ohh, ouch. When that happened to me, I just used through bolts. Am I setting myself up for problems? (Why aren't you a fan of through bolts?)

In that case, punch it out and use a smaller bolt that barely fits. It's sloppy but it will work. The press in studs are better, but cost more than the bolt.

Punch them oversize and get studs that are larger on one end than the other. This one from Grainger is 3/8 - 16 on one end and 1/2 - 20 on the other; cost about $2.

http://www.grainger.com/Grainger/wwg/start.shtml

dculberson wrote: Ohh, ouch. When that happened to me, I just used through bolts. Am I setting myself up for problems? (Why aren't you a fan of through bolts?)

Mostly just me being fussy, probably for no good reason!

If you can access the top to get a bolt through, its not a bad solution. Chrysler did it for many years on the V8s. Just use good bolts and stover nuts.

Helicoil or oversized studs isn't bad, either.

I'd not oversize the stud the meat is likley to thin allready. Go through bolt with SS bolts and Brass nuts that way next time you service it if the threads are toast the brass will strip away and come apart.

44Dwarf wrote: I'd not oversize the stud the meat is likley to thin allready. Go through bolt with SS bolts and Brass nuts that way next time you service it if the threads are toast the brass will strip away and come apart.

Can you elaborate on this? This was actually going to be my next question... what hardware do you all suggest?

I have deep love for flanged nuts, but I don't know if they are technically any better than standard nuts.

If there's room to access everything, I'd go with through-bolts. Easy, cheap, and IIRC from Carroll Smith's book, that's the strongest of the three fastener methods (slightly better than a nut on a stud, much better than a bolt in a blind hole). Only downside is that it's hard to safety-wire them, but it sounds like that's not an issue in this case.