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Why NOT to let your head be 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. HN# Date CAST#G6EW NOTES: IV stock New thickness 5.200 EV stock Min thickness 5.185 (AREA SPEC) EVO 8 Cam Gears Combustion Chambers Bolt Holes 4 3 2 1 5 4 3 2 1 10 9 8 7 6 Head Thickness 5.187 Head Thickness 5.184 Head Thickness 5.189 Head Thickness 5.188 If you look at the 4 corners, you will see how the head gasket surface is not parallel to the valve cover rail. It is close, but still off 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. |
Re: Why NOT to let your head be Belt Surfaced
LOL who ever thinks belt surfacing is a good idea on anything that needs to be even close to flat is high.
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Re: Why NOT to let your head be Belt Surfaced
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Re: Why NOT to let your head be Belt Surfaced
I just beat it flat with a large hammer.
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Re: Why NOT to let your head be Belt Surfaced
I just like to beat it.
I belt sanded my turbo fitting, works great for the last year. |
Re: Why NOT to let your head be Belt Surfaced
Aww come on that just the wrong way of doing things. OYu should use a brass malet!
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Re: Why NOT to let your head be Belt Surfaced
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I would think there is a bit of diffrence between the surface needed for a turbo fitting (oil return I would guess) and the finish needed for a head gasket... |
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