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  #1  
Old 01-19-2003, 01:28 PM
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Join Date: Mar 2001
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230/4 123 1976 cylinder head

dear Colleagues

This old car has had its head reskimmed following a dislodged valve seat and consequent complete overhaul. A comment was made by the machine shop that perhaps a thicker gasket should be used as over a millimeter had collectively been machined off the face.

What is actually being said> Can a valve hit a piston? If so are thicker gaskets available? Can 2 be used one above the other?
Can a spacer metal gasket be fitted to win back lost meat?

I shall be extremely grateful for some guidance and how to approach this problem, and hope that i don't have to buy a new head since this one now is completely 'new' barring the risky (?) loss of dimension.

Many thanks

Ed
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  #2  
Old 01-19-2003, 01:58 PM
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Location: Gainesville FL
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The most common problem with cutting the head too much was that the timing chain becomes too long and is hard to tention.

I have heard of people shimming the cam towers but never the head itself. I doubt that valve clearance to pistons will be a problem. The head has a minimum thickness and if more than a mm has been removed then it has been exceeded. I would measure and check against the spec. If you are within .010in of the standard I wouldn't worry, put it together.

But, figuring that you are rebuilding the whole thing I would really worry about using a head that had a seat drop. That only happens after extremely overheating and with the thickness problem you are risking a bunch by reusing it.
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Steve Brotherton
Continental Imports
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  #3  
Old 01-19-2003, 03:13 PM
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thank you Steve

Yes--I keep learning.!! The head was overhauled a few months ago and required some welding to improve gasket sealing.

The seat dropped after about 100 miles later, and the machine shop said that one of the causes of this could have been welding fairly close to the problem seat--that the heat slackened it off.

So now it has been completely renewed with new seats, and valvestem seals --plus skimming (again).!!

So I have this perfect head with this question mark over it being 1.1 millimetres thinner than when it was born.

Seemed like a thicker gasket might be a good insurance idea.

What would indicate that the chain tensioner was beyond it's limit?

Many thanks for your support on this.

Ed
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  #4  
Old 01-19-2003, 03:48 PM
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Basically the issue comes down to performance. The chain will rattle at times if the adjuster is at its limit.

If you are at 1.1 don't worry about it. That is only 0.004in over the limit and like I said before it will work OK. I have done it.

Was the head planed on both sides. This is important as the top surface will still be warped if it hasn't been planed. There won't be room for another cut! The cam will bind if the head isn't flat on top.
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Continental Imports
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33 years MB technician
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