Why not to let your head be belt surfaced/sanded
This issue can be found on ANY belt surface/sanded head!!
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
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.
HN# Date
CAST#G6EW NOTES:
IV stock New thickness 5.200
EV stock Min thickness 5.185 (AREA SPEC)
EVO 8
This is the surface finish left by a belt sander
(http://i261.photobucket.com/albums/ii49/BogusSVO/4G63T%20head/Picture123.jpg)
This is how the surface looked after I milled appox .002
(http://i261.photobucket.com/albums/ii49/BogusSVO/4G63T%20head/DSCF4363.jpg)
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.
(http://i261.photobucket.com/albums/ii49/BogusSVO/4G63T%20head/DSCF4362.jpg)
I made another pass of about .002
This is how it looked.
(http://i261.photobucket.com/albums/ii49/BogusSVO/4G63T%20head/DSCF4369.jpg)
I made another .002 cut
And was to this
(http://i261.photobucket.com/albums/ii49/BogusSVO/4G63T%20head/DSCF4370.jpg)
So one more pass to clean the gasket surface, and proper clamping force will be kept on the head gasket.
(http://i261.photobucket.com/albums/ii49/BogusSVO/4G63T%20head/DSCF4372.jpg)
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.