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Head bolt reuse, EM studs, etc.
As we're all aware there are two sets of directions for reuse of head
bolts -- "do" and "don't". Just made an interesting discovery that I'll share
with the list. This may have been here before, but I haven't seen it.
I've taken apart four turbo engines recently. I kept a few of the bolts
from each since I was planning only to use new ones (per comments by Phil
Payne and others). I just compared the bolts I removed from the new head
bolts I had ordered. They are not the same.
The bolts I removed are basically the same length as the new ones. As
someone else had observed, after the first inch (the section threaded into the
block) the pitch changed and the threads would not line up exactly with the
new bolts. The diameter of the old bolts is 0.430" from the bottom of the
head to the top of the threads. The new bolts are 0.430" for a quarter inch,
then taper to 0.390" to the top of the threads.
If I were guessing, I would guess that the "do" comments are related to
the "old" bolts, the "don't" comments would thus apply to the "new" ones I
Personally, I don't think I want these new ones in my engine, they would
seem to be more likely to stretch (which I realize is part of what they are
supposed to do). I'd put the "old" ones back in first.
No, I'm not going to, that's just an observation. I've already ordered
more from another place, hopefully they'll be different. If not, I'll keep
ordering until I get what I want.
On to exhaust manifold studs. Someone (Igor Kessel, maybe?) observed
that with Audis, it's not "if" the em studs break, but "when. I noted that
the engine I just got had two broken studs, so I decided to pull the rest and
replace them, per the advice of the list. I now have FOUR broken studs, which
effectively verifies the if/when statement.
The head goes to the shop on Monday to have the four studs drilled out
and heli-coils put in. Question to those who've had to put in heli-coils --
does that make it any better? If it does I'll just have them punch out and
rework all ten at once.
Imperial Potentate, Bucksnort Quattro Club (Un-Inc.)