2001 Malibu head bolt torque

This is another follow up on the replacement of head gaskets on the 2001 Malibu. I got the new torque to yield bolts from a Chevy Dealer. I found that the complete top end gasket set from Federal Mogul, does not include a note about the need to use new Torque to Yield Bolts. Interestingly enough, when you purchase their head gasket only set, there is a warning noted on the packaging of this set about head bolts. The note further explains that you need to reference a master catalog for further info. The independent dealers do have access to the Torque to Yield Bolts for some savings in pricing above what the dealers are generally willing to offer.

I removed all of the reused head bolts. (this is after the first attempt in following the procedures listed by Haynes Repair Manual) I chose not to reuse the head gasket over, but instead considered the gaskets damaged by trying to use the original head bolts over again. After setting a new head gasket, and installing the new Torque to Yield head bolts, I could clearly feel the difference. The consistency of pressures needed to turn the wrench the 95 degrees, following the Torque of the bolts to 37 lb., was very clearly evident.

I hope this experience will help some one out in the future.

DW
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"DW" wrote in message

> This is another follow up on the replacement of head gaskets on the
> 2001 Malibu. I got the new torque to yield bolts from a Chevy Dealer.
> I found that the complete top end gasket set from Federal Mogul,
> does not include a note about the need to use new Torque to Yield
> Bolts. Interestingly enough, when you purchase their head gasket only
> set, there is a warning noted on the packaging of this set about head
> bolts. The note further explains that you need to reference a master
> catalog for further info. The independent dealers do have access to
> the Torque to Yield Bolts for some savings in pricing above what the
> dealers are generally willing to offer.
>
> I removed all of the reused head bolts. (this is after the first
> attempt in following the procedures listed by Haynes Repair Manual) I
> chose not to reuse the head gasket over, but instead considered the
> gaskets damaged by trying to use the original head bolts over again.
> After setting a new head gasket, and installing the new Torque to
> Yield head bolts, I could clearly feel the difference. The consistency
> of pressures needed to turn the wrench the 95 degrees, following the
> Torque of the bolts to 37 lb., was very clearly evident.
>
> I hope this experience will help some one out in the future.
>
> DW
>
> "DW" wrote:
> > Further study on the problem has me feeling Haynes Repair
> > manual for the Malibu 1997 through 2003 may be in error
> > suggesting you reuse the existing head bolts. There is nothing
> > noted about the head bolts being torque yield bolts. These
> > head bolts as it turns out are torque to yield bolts and the
> > Chevy parts guys and mechanics I have been able to talk to,
> > suggest that that is the source of my problem and I need to
> > use new bolts. There is some feeling some are using them over
> > once and only once, but the mechanics I have talked to are not
> > doing any thing but replace the bolts and do not wish to risk
> > using them over. There are some finding broken head bolts
> > comming into the shop from time to time suggesting there is a
> > stretch life on the bolts but no one was sure about that. It
> > just may be there is a failure rate with these bolts due to
> > what they are. Due to inconsistant Torqing as noted in my
> > question, I am putting new Tork to yield bolts on

I found this procedure strange at first, also. If you study it, you will
find that it was developed because torquing with a torque wrench does not
give predictable or uniform pressures on the head to the same degree of
accuracy. The whole purpose of tightening a bolt is to elastically stretch
the bolt and thereby apply (and maintain) pressure on the joint. By
controlling the stretch (yield) of the bolt you can get and maintain a known
pressure pretty consistently.

My first exposure to this principle was on 50's Triumph motorcycles where
you used a micrometer to measure the stretch of the connecting rod bolts to
determine the proper tightness.

Don Young
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