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cylinder head rebuild
I have a question for the 944 gurus and all others. I recently had two cylinder heads rebuilt one from a 1984 944 and one from a 1986 944. the builder called me back and said that the shims were different and wanted to know why. Question is why would there two types of shim thicknesses from one head to another and where can i buy the proper spec shims to replace the out of spec ones? thanks in advance.
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08-26-2009, 05:24 PM
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Join Date: Apr 2007
Location: Buffalo, NY
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Two different heads. One could have been cut more then the other if it was warped. If one was cut 0.005" and the other was cut 0.010," then the 0.010" head would have an extra 0.005" of shim height then the 0.005" head.
I am a Die Maker by trade and you have to keep track of the shims as now the heads are somewhat customized once they cut them, grind them, whatever they do to them to bring them level. We always have to keep our parts well separated as we have to grind them many times over the years and add new shims each time to take it back to the proper height. I hope that made sense if I understood your question correctly. 
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John '87 944 N/A (first Porsche) '95 E-350 Diesel '03 S-Type Jag 3.0 '03 Taurus SES '06 Eddie Bauer Explorer RIP SoCal |
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08-26-2009, 05:44 PM
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thanks for your reply, that makes a lot of sense. next question is should I go ahead and have him rebuild the head anyways? I believe one of the head were rebuilt in the past and was just concern if the thicker shim would cause any damage.
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08-26-2009, 06:48 PM
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Thicker should not be a problem as far as the interference of the valves and the pistons. I do not know much about machining heads, we are Die Makers, but I would think that the head would have some kind of reference point to measure from.
If there is anyway to figure out which head in "thinner" then I would guess the bigger shims to go with that head. Are their any distinct markings, stains, gouges, or anything that you can tell which head goes with which shims? In the future, mark all shims and their locations for anything that has a shim.
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John '87 944 N/A (first Porsche) '95 E-350 Diesel '03 S-Type Jag 3.0 '03 Taurus SES '06 Eddie Bauer Explorer RIP SoCal |
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08-26-2009, 07:06 PM
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Redline Racer
Join Date: Jan 2007
Posts: 2,444
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what shims are you refering to? The shims under the valve springs? If so, they only need to be changed or added to if the valve seats are being re-cut or replaced. They are simply to maintain the correct installed height of the valve springs, if I understand correctly.
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08-26-2009, 10:12 PM
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winter-hater club member
Join Date: Oct 2003
Location: salt lake city, utah
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i am a little confused here.
how would machining the surface of the head have anything to do with the shims at the valves? these are two separate surfaces: valve seats vs. head level.
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08-26-2009, 10:50 PM
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I misunderstood the question.
SORRY!
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John '87 944 N/A (first Porsche) '95 E-350 Diesel '03 S-Type Jag 3.0 '03 Taurus SES '06 Eddie Bauer Explorer RIP SoCal |
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08-27-2009, 06:03 AM
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