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Discussion Starter #1
Why not to let your head be belt surfaced/sanded

This issue will be found on ANY belt surfaced/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



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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I can't believe anybody would let somebody put a belt on a precision machined surface.

There is NO substitute for machining.

I've been around a lot of machine shops and have a great deal of respect and admiration for a good machinist. Machining is truly an art.

I'm surprised you only had to take .008" off of it to find the bottom of the hack belt surface/sand job. I would have expected an even more uneven finish.
 

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lol wow, the only thing ive ever used a belt sander at work for is exhaust manifolds and weight balancing rods, never heard of heads before and now i know why :facepalm:
 

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Thats pretty unbelievable. So in what instance would you use a belt surfacer to do any work? Just curious. Thanks for the pics and tips!
 

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belt sander ???????????????? what the hades am i on this old house .com ?????????????? or maybe i'm on my ford truck site talking about the new wood for my bed thats it !!!!!!!!!! i misread the post it wasn't head it was bed ...................... sheez maybe someone ought to pass the shops name on so no one else has to go through that .:(
 

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There are MANY old engines out there that have had the surfaces "finished" with a belt sander that are perfectly fine. It is a matter of "acceptable" vs. "optimal" vs. the application.

(When I say "belt sander" I mean this: http://www.mtecobra.com/belt_sander.htm, not this: http://benchmark.20m.com/reviews/RidgidBeltSander/RidgidBeltSander_BeltRelease.gif )

For an example, a steel head on a steel block (like the millions of Ford and Chevrolet engines out there), in a non-performance application, can work perfectly fine with a finish like that from a belt sander.

But an aluminum head…. No way should it have been taken near a belt sander. :zbash:

I do have one question:

BogusSVO said:

The customer was told it was surfaced .003-.004
It was then run and the bottom end failed
If the bottom end failed, how was it related to the head surfacing?
 

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Discussion Starter #8
94 Daily... it spun a rod bearing, the customer bought another engine and was selling the head, the head had less than 500 miles on it when the bottom end failed, he brought me the head to look at and check before he sent it out .
 

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Discussion Starter #9
exhaust manifolds and headers are about the only thing that should be surfaced on a belt surfacer.

94 daily is about on point about the cast iron head/block "stock" performace engine. if a composite gasket is being used
but even then, I will change the set up of my machine so I can mill cast iron.
Maybe I am just being a PITA, I just do not like a belt surfacer....

This is the one I use...

http://www.joebakerequipsales.com/AutoI1000.htm
 

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I agree 100% and I wasn't contradicting you or anything. :thumbsup:
 

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Discussion Starter #11
I know bro! all is well with the world.

I just know I can be a picky sob at times, any decent/good/repupital machinist would agree
 

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Thanks for the info BogusSVO. This is very interesting to me for sure.
 

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Not to be an arse, but it looks like your machine head is slightly out of square. The reason I say this is I don't see any witness marks from the backside of the cutter. This would leave the center of the head slightly lower than the outside.

/ anal machinist...

:D
 

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Discussion Starter #15
it is a single blade machine, with a taper bit, the work head is tilted 5* so it will not leave marks like discribe
 

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Discussion Starter #17
guess what... seen heads being "surfaced" with one... but the best one was when I lived out in MO..... 2 jack leg guys had tied a rope to each end of the head, weighed it down with a bag of oil dry and was pulling it back and forth across the shop floor!!
 

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ROFLMAO

Your surfacer looks very similar to our grinder at work.
 

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Discussion Starter #19
bowez.... its the same basic design that was used for years as a wet segment sone grinder, they just updateded the cutter head and controls.

I do not find that surprizing, you run a Berco?
 

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I have had plenty of cast iron heads done on a quik-way, but not one used for misc stuff (exhaust manifolds etc...) It has to be set up for surfacing heads only. Aluminum heads I wouldn't do that to they really need to be milled.
Alan
 
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