Why NOT to have your cylinder head Belt Surfaced
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Evolving Member
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From: Pensacola,Fla
Why NOT to have your cylinder head Belt Surfaced
Why not to let your head be belt surfaced/sanded
The subject head is a Mitsu 4G63T from an Evo VIII
This head was in very good shape to start.
The head was pulled due to a bottom end problem.
It was not overheated.
It was taken to another shop, NOT mine.
The customer was told it was surfaced .003-.004
It was then run and the bottom end failed, Then came to my shop.
The first thing I did was to check the thickness of the head.
I know a belt surfaced head will not be parallel nor square along with not having the proper surface finish for a MLS head gasket.
This is the surface finish left by a belt sander
This is how the surface looked after I milled appox .002
It did cut most of the surface, but it was still low at one corner, and it would happen to be right around the oil feed port to the head.
I made another pass of about .002
This is how it looked.
I made another .002 cut
And was to this
So one more pass to clean the gasket surface, and proper clamping force will be kept on the head gasket.
I measured the head again, and it was 5.183 at all 4 corners
When I cc’ed a combustion chamber it was 44cc
I also did “oil port mod #1” before I surfaced the head.
This head is now .002 below AREA min spec, but is still a useable head.
i dont trust alot of local shops .
Thread Starter
Evolving Member
iTrader: (1)
Joined: Mar 2010
Posts: 173
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From: Pensacola,Fla
Ask And I post 
https://www.evolutionm.net/forums/en...l#post10536623
Thats why I post, alot of machine shops use old out of date equipment, or equipment that is just not up to the job.
Surfacing is the biggest issue, more so nowadays with how common MLS head gaskets are.
But some shop equipment is still good and valid to use today as it was back in the 1960's or 1970's when the equipment was first produced.
A rod machine made back then is still good to use today, the way a rod is sized on the big end has not changed.
https://www.evolutionm.net/forums/en...l#post10536623
Thats why I post, alot of machine shops use old out of date equipment, or equipment that is just not up to the job.
Surfacing is the biggest issue, more so nowadays with how common MLS head gaskets are.
But some shop equipment is still good and valid to use today as it was back in the 1960's or 1970's when the equipment was first produced.
A rod machine made back then is still good to use today, the way a rod is sized on the big end has not changed.
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