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Old 03-20-2012, 11:14 PM   #1
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Default 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.

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.
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Why NOT to let your head be belt surfaced-picture123.jpg   Why NOT to let your head be belt surfaced-dscf4363.jpg   Why NOT to let your head be belt surfaced-dscf4362.jpg   Why NOT to let your head be belt surfaced-dscf4369.jpg   Why NOT to let your head be belt surfaced-dscf4370.jpg  

Why NOT to let your head be belt surfaced-dscf4372.jpg  
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Old 03-20-2012, 11:20 PM   #2
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Happy to see a shop give a F--- and measure things. Now if I could just find a local place to do machining that wasn't full of morons I'd be set.
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Old 03-21-2012, 12:12 AM   #3
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lol @ ghetto machine shops.
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Old 03-21-2012, 12:20 AM   #4
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That is pretty lame. BTW, see if you have a macro mode (flower icon) on whatever camera you're using. It would help tremendously with your photos. Bring it into a well-lit area if you can. More light=better focus, shorter exposures, and more depth of field.
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Old 03-21-2012, 11:19 AM   #5
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and turn off the flash when taking pictures of shiny stuff.
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Old 03-21-2012, 11:31 AM   #6
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a belt sander?
jesus
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Old 03-21-2012, 11:33 AM   #7
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I have an old Fujifilm Finepix 4 mega pixel camera I use around the shop.
From what I can remember I did not use a flash, I just have alot of lights up and on in the shop.

phillyb.. It is a belt surfacer, but it is nothing more than an overgrown belt sander, alot of machineshops have them and use them, they can do OK for a cast iron head with a composite gasket.

They are cheap to buy $10k and under new, and take very littler training to use, and they are quick to use.

But they mangle alum heads 99% of the time.

Last edited by BogusSVO; 03-21-2012 at 11:45 AM.
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Old 03-21-2012, 11:50 AM   #8
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unbeleivable. that is janky as ----.
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Old 04-19-2012, 11:28 AM   #9
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A couple of internet pics of belt surfacers.
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Why NOT to let your head be belt surfaced-spn800.jpg   Why NOT to let your head be belt surfaced-beltsander.jpg  
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Old 04-19-2012, 04:48 PM   #10
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Bogus, any reason you aren't a vender on the forum? You seem to pretty competent at your craft, something I think alot of people struggle to find locally.
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Old 04-19-2012, 04:57 PM   #11
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What is your plan for the valves that are now exposed? In one of the pics before they were removed, it looked like there was a bit of contact with the mill and valves.
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Old 04-19-2012, 05:09 PM   #12
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Luke..... I just came here to learn about the 1.8l, and share some of what I know and do. I am a small one man shop.

Maiter.... Honestly, I can not say what I did to fix the 2 valves that I tinged, it has been a few years since I orginaly wrote this.

But knowing what I do of hot spots and trubos, I proberly pitched the valves and grabbed a coupple stock used replacements and seated them in.
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