[V6-12v] More on V6 Head Bolt re-torque

apowell at colocougs.org apowell at gocougs.wsu.edu
Sun Sep 12 14:27:20 EDT 2004

I have the valve covers off my 1993 90Q V6 (2.8L), with the intention of tightening the head bolts
1/4 turn as directed in the factory manual after removing and replacing the intake manifold.

Two problems:

1) The bolt heads are only about 11 MM, and they are not octagonal. They are star-shaped. I don't
have a socket to match these heads.  Anyone know whether this bolt head design has a specific name
(ala Torx or other distinguishing ID) to help me find the correct socket? Also, any idea where I
might buy a socket designed for these bolt heads?

2) The factory torque spec on these bolts is 44 lbs/ft. Compared to the torque on US V8 motors, this
seems like pretty light torque to me (even the head bolts on my 1958 Fiat 1200 with aluminum head
torqued to 58 lbs/ft). However, I gently tried tightening them with a half-inch drive breaker bar
(despite my concern voiced in #1) and they do NOT want to budge. I'm EXTREMELY reluctant to put a
lot of torque on these, and I'm sure I tried at least 60 lbs/ft without moving them a bit. What's
going on??? I know they might have to break loose, but this seems like a lot of torque for bolts
spec'd at 44 lbs/ft. If I turn them 1/4 turn, based on the force I already used, my guess is that
after another 1/4 turn those bolts will be torqued to around 100 lbs/ft. I'm afraid the heads will
shear off at that torque.

Has anyone BTDT with this procedure?

I received contradictory comments about how to go about tightening the bolts on these heads. One
lister suggested I should break them loose, then re-torque to factory torque plus 1/4 turn. Others
noted that these are "stretch" bolts and are intended for one-time use, so I should just turn then
1/4 turn, which is the process as per the factory manual. It seems to me that if the bolts are
designed for one-time use, I should NOT loosen them and then re-tighten them. Heck, one lister
suggested I turn them 1/2 turn! That would put them at 150 lbs/ft or more, which makes no sense.

I decided to leave it parked until I can find an appropriate socket for the bolt heads AND figure
out what to do.

Would the best move be to buy new bolts and replace them one by one in each head so that I know I
won't have any problem with them? Or should I get the socket and turn them another 1/4 turn?

Al Powell
apowell at gocougs.wsu.edu
1958 Fiat 1200 Transformabile Spyder
1983 Datsun 280ZX Turbo
1993 Audi 90Q
1997 Chebby Blazer
1999 Chebby Blazer

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