500, 472, 425, 368 Discussion, 425 cylinder head bolts in Cadillac Engine Technical Discussion; Hey guys,
I'll have to change the head gaskets on my 425, I was wondering about the cylinder head bolts, ...
I'll have to change the head gaskets on my 425, I was wondering about the cylinder head bolts, is it safe to keep the old ones provided the threads are still fine or should I get new ones in any case?
I couldn't find anything about that anywhere.
And any advice on how to safely remove the exhaust manifold bolts, it looks like they're already one with the heads...
Automobile(s): 1977 Coupe (blue), 1977 Coupe (yellow), 1977 Coupe (green)
Re: 425 cylinder head bolts
I would drop the exhaust manifold header pipe, or Y pipe from the manifolds and remove the heads with the manifolds attached. You will most likely have problems with the exhaust manifold bolts. If the hex will fit a socket and you can get to them with an impact wrench, you may be able to get them to come out and not snap them. If you have a hand held impact driver, you may try striking it with that first. Do not over heat the bolt, it will just become more brittle than it already is, and harden more, making it impossible to drill out without a carbide drill bit.
The head bolts are not like the later manufactured bolts that were engineered for limited stretch and therefore one time use. Check the treads to ensure they are not rounded, burred, cracked, or sharp on the face edge. I clean them on a wire wheel before re-installing them and inspect them very close with scrutiny. Check the bolt body for signs of stress. If the body is smooth without evidence of stressing, the bolt is good to go.
If you have an older Motor's Manual, there will be a section in there, with ilustrations, on how to inspect these bolts.