3406 exhaust manifold stud hole depth

I attempted to remove the old studs. It didn’t take long to decide to leave them in. Most likely they’ll break, and you’ll be drilling them out. I learned a lot doing this job.
Don’t waste time with bolt extractors. They break and your in for twice the work.
Left handed drill bit is your friend.
Use a jig that will center you on the broken stud. If that’s not available use a center punch, and be very patient keeping centered on the stud. Drill straight!
Holes are about 7/8 deep. Don’t go through into the water jacket.
Try to keep the bit smaller than the size needed to retap the holes. I was able to salvage 3/4 holes without a helicoil.
Other than the broken stud removal it’s a simple job. Can have the manifold off and on in half an hour.

 

Cat sells one, you can make one using the manifold as a guide. I used the center punch and lots of patience method.

I put new nuts on. If I did it again I’d use aftermarket parts. For 6 exhaust gaskets, one exhaust sleeve, bag of studs, bag of nuts, thermostat housing gasket, three stud spacers, and a turbo return line o-ring it was $330. I’d use softer bolts from the hardware store next time so when they inevitably brake they are easier to remove. The torque spec is 28 ft lbs, and the lock nuts keep them from loosening up. The manifold is suppose to be able to expand and contract so it doesn’t break the studs. Make sure your slip joints aren’t bound up. I pulled my manifold apart to wire brush them then coated the joints with anti-seize. So far it’s working good.

 

The nuts came off easy with an impact, and some penetrating oil.

 

Exactly what happened to me. I used a tap to clean the threads up which worked on 3 of the 4. Try to avoid going too big with the bit.