replacing driver's side head on a 455

rgogan

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Sep 20, 2004
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Compression loss was from head gasket web failure between cylinders #5 and #7. I believe this was from inadequate torque on the head bolt at that
location. Found that all the head bolt bores in the block were the same depth but on chasing the threads found that the threads did not extend deep
enough on the bore in the block on the outboard side between #5 and #7. Confirmed this by looking down the bore. Dealt with it by putting a Grade #8
thick washer under that head bolt. I could have cut the bolt shorter or tapped the hole deeper with an end tap, but this was the simplest solution.
All the bolts torqued down as expected.
Now I am dealing with the aluminum intake manifold which is turning out to be less than perfect. New post to follow.
 
Robert,
Most of us that know engines see no advantage to coat the Al. intake.
Yes Al. Oxidizes more than steel, but you should be more concerned about
sealing the intake to the head as that is where lot of problems develop.

On Thu, Jun 24, 2021 at 8:05 AM Robert J. Gogan
wrote:

> Compression loss was from head gasket web failure between cylinders #5 and
> #7. I believe this was from inadequate torque on the head bolt at that
> location. Found that all the head bolt bores in the block were the same
> depth but on chasing the threads found that the threads did not extend deep
> enough on the bore in the block on the outboard side between #5 and #7.
> Confirmed this by looking down the bore. Dealt with it by putting a Grade
> #8
> thick washer under that head bolt. I could have cut the bolt shorter or
> tapped the hole deeper with an end tap, but this was the simplest solution.
> All the bolts torqued down as expected.
> Now I am dealing with the aluminum intake manifold which is turning out to
> be less than perfect. New post to follow.
> _______________________________________________
> GMCnet mailing list
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Jim Kanomata ASE
Applied/GMC, Newark,CA
jimk
http://www.gmcrvparts.com
1-800-752-7502