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Head bolts - do not reuse!
The head is back on the car. For the first time ever I assembled the
head completely on the bench, together with EM, IM, Turbo, WG, Bellow,
Downpipe etc and installed it on the block as one piece.
Yes, you need two Hulk Hogans for helpers to do that (rising the whole
enchilada on shoulder level, tilting it and fishing the downpipe under
the RH half-shaft is very entertaining), but it allows you to torque
every bolt to spec while on the bench, where everything is exposed and
the installation itself is at least two times faster.
I was abut to reuse the head bolts on my 200. Bentley explicitly allows
to reuse the bolts on the 3B engine and does not say anything about the
MC engine. I figured if a more stressed 3B does not break the once used
head bolts, the MC is even less likely to do so.
OTOH, Scott QSHIPQ and Mike Z in lengthy telephone conversations (thanks
a lot, fellows :) both insisted that I replaced the 10y/o bolts with
either Raceware studs or at least new OEM.
I followed the advice and ordered the bolts (@$2.36/ea hardly an
expence). When I got the bolts the first course of action was to compare
the old ones to the new ones.
The new OEM bolt was right on the spec: M11x1.5x98mm.
The old one was 3mm longer!!!
I matched up the beginning of the thread and could see that by the
middle of the threaded portion the accumulated thread pitch error was a
FULL PITCH! In other words, the pitch on both bolts was so much
different that they couldn't be interlocked with one another.
Folks, don't listen to Bentley in this issue. If you pull the head -
install new head bolts!
'89 200TQ -- 18psi (TAP)