From: Ray Fougnier (rfougnier@comcast.net)
Date: Sat Jan 17 2004 - 05:50:53 PST
Good point. You should replace head bolts when putting the head back
on. You could get away with one re-tourque, but you don't know the
history of what's there now. Head bolts are supposed to stretch when
you torque them and in doing so, make the tensile strength go up due to
work hardening. At some point, the bolt won't stretch any more because
you stop torquing before the new, work hardened, tensile strength is
reached.
Bill Kealey wrote:
>
> Also, from my personal experience with my engines (two so far) don't assume
> that exhaust gasses in the water or sudden overheating is a major problem.
> If the head has been removed and the old bolts reused you may have problems.
> Both of mine did. The problem is that the bolts may not hold up when
> re-torqued after removal. I don't know a thing about metalurgy but do know
> that the bolts become weak after years and years of use. In fact one of my
> engines actually bent enough in the middle during idle speed warmup when I
> first put it in that it cracked the top of the radiator when the head gasket
> opened a gap between the center two cyls. and water jacket. I removed the
> head and took it to a local shop where it was checked for cracks and
> warpage. No problem. The shop manager recommended that I replace the head
> bolts and try again. Worked perfectly. I later damaged the engine through
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