Hello, I have stripped some threads from the exhaust manifold bolts on my 1994 LT1 cylinder heads. Now that the heads are off for spark plug repair I would like to install studs to ensure I don't strip out the bolt holes reinstalling exhaust manifold bolts. I have purchased these studs from Dorman. They are M10x1.5 but are tight to start in the bolt hole and seem to be reaming the threads.

Has anyone used these on LT1 heads, should they be this tight to screw in? Did you use a stud installer or just use two nuts to drive it? Should I use ARP thread sealant?

Thanks for any input!

 

I don't think these are the right size, I am not going to proceed. Looks like the exhaust bolts should be 3/8"x16?

 

I think that 3/8"-16 are correct.

 

If you are talking the exhaust manifold studs in the flange yes I have used Dorman 03133 they are metric and they fit properly. I had a couple break when I changed my exhaust.
The exhaust header bolts are SAE I believe though I have never changed those.

 

SAE 3/8"-16 for exhaust manifold to head

The Dorman studs you linked in post #1 are for the manifold outlet flange to y-pipe connection

 

Well that explains it, thank you. Just checked and those will now work for a simpler to work with connection to y-pipe. I have not found 3/8"-16 studs at correct length and was going to look into ordering from McMaster. Any other place to purchase those? If I do order threaded 3/8"-16 rod lengths to use as stud, what grade/material is best? Will a stud installed be necessary? Should I use ARP thread locker? Thanks!

 

Are you sure the manifolds (or headers?) will provide sufficient room to get the nut over the projecting stud threads? Additionally, many header bolts have “small” hex (or 12-point) heads, providing more room for wrench access. A full-size nut over a stud just results in less clearance.

 

This is what I'm about to do, and I haven't found the exact bolt/stud kit for both the stock manifold to header studs/bolts, and the studs/nuts for both y-pipe collector flanges.

I suspect I may break at least the y-pipe studs, even though I'm soaking them like crazy. Once I get them out, a muffler shop should be able to install new ones yeah?

 

I plan to reuse the 8 spacers if no one knows of a kit that has them.
For the manifolds, the bolt/stud kit should look something like this:

 

Right, I will take some more measurements and check bolt/nut clearance on the rams-horn manifolds first. Sounds like I need to plan on going back to bolts though I am concerned about some threads in the heads that stripped out last time I removed them. If I go back to bolts I will need to order lower grade ones as the Grade 8 I previously used may have caused those threads to strip out.

 

Grade of bolt shouldn't affect whether they strip the aluminum head threads or not. Dimensionally, they should all be the same. Threads may be rolled on a higher grade bolt, not cut, but that shouldn't increase tendency to strip. Insure they go in straight, make sure they are long enough, don't over torque them. Use a dab of anti-seize compound. I run ARP 12-point stainless steel header bolts, which are actually stronger than Grade 8. Never had a problem. If you are set on studs, I believe ARP makes them.

While the heads are off, have the bolt holes inspected and reconditioned as required.

 

Ok I will go with ARP 12pt header bolts and get started on bolt hole inspection and reconditioning. Thanks!

 

I went almost all 12 point bots on my car, but went 6 point for the headers from Kooks with smaller heads (5/16th). The challenge for me was that the primaries on 2, 3, 5 and 6 were so tight, that I was only able to get the open side of a wrench on the head. I was fairly bummbed because I already had the 12 point bolts.