How to not snap off manifold bolts?

[Stephen Trapani]

I'm not sure if it's a good idea to reproduce this question here as well as in Ask All Sailors. Some of you may know I snapped off three out of four bolts in my exhaust manifold on my 2qm15. Here is the thread from that:

http://forums.sbo.sailboatowners.com/showthread.php?t=131381&#post828090

I think I can get the manifold studs out with an extra nut, to save me trying to get out the broken bolts in the very tight quarters, but I don't want to break the studs off in the block. I couldn't just slide the manifold off the studs due to lack of room. What precautions should I take?

 

[bria46]

I tried this product on rusted automotive exhaust/manifold bolts and it was GREAT!!!

www.loctitefreezeandrelease.com/

 

[Jake N Eggs]

Stephen, pulling the studs without breaking them is a feel thing. Thread the first nut on to the stud far enough to allow the second nut to be fully engaged on the threads of the stud. Back the first nut to the second nut and use two wrenches to tighten the nuts together. Use a wrench on the first nut and try to unscrew the stud. The stud will have some torsional twist as it tries to break free from the engine head. This is where the feel comes in. Studs are usually tight on a shoulder or sometimes they are set in with Loctite. Try an easy one to get to first. Good luck.

 

[Johnb]

Don't feel too bad - when I broke off the exhaust manifold to elbow bolts on my boat it was so effortless a baby could have done it. There was just no way those bolts were going to undo, they were just plain knackered, so that may be unavoidable.

For reasons that I no longer remember, I was told that when you are tightening up studs it is important to avoid having the stud turn when torquing the nut, so you want to make sure they are properly bottomed before tightening. This can be achieved by usung the technique described above - tighten two nuts together to form a locknut and then use that to drive the stud home. Also it is good practice to make sure the threads on stud and hole are clean and free of grit, bits of rust etc.