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Re: Torquing head bolts

To: Martin Scarr <martins@efn.org>
Subject: Re: Torquing head bolts
From: Trevor Boicey <tboicey@brit.ca>
Date: Tue, 06 Oct 1998 03:23:32 -0400
Martin Scarr wrote:
> 
> Maybe a bit off topic here, but I ran into something that's puzzled me.  I
> helped my son-in-law do head gaskets on his '90 Nissan Maxima with the 3.0
> SOHC motor.  This is an iron block V6 with aluminum heads.  The Haynes
> manual says to torque the head bolts in 5 steps:  23 ft-lbs, 42 ft-lbs,
> loosen all bolts, 25 ft-lbs, 47 ft-lbs.
> 
> I've never seen this 'loosen all bolts' step; it doesn't make sense to me.
> Anyone have an explanation?

  It almost seems like they are trying to "set up" the gasket with
a bit of compression, then let it settle, then bring it up to
torque. This would probably make sense with a copper gasket but
I don't see what it would do for an asbestos one.

  Torque on a new head gasket is kind of a crap shoot anyways,
when you bring the engine up to temperature the first time
you need quite a lot of retorquing anyways.

-- 
Trevor Boicey, P. Eng.
Ottawa, Canada, tboicey@brit.ca
ICQ #17432933 http://www.brit.ca/~tboicey/

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