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| joeld | Bore size of GM head gasket | ||
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Guru
 
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Is the GM gasket #12557236 a 4.0 inch bore or is it a 4.10 inch bore size? My engine is 40 over and I'm installing head gaskets because of a small external leak at #5&7.
I know most Fel-Pro gaskets are a 4.166 inch bore size, but I would prefer to use the composition from GM. I was thinking someone might have actually measured one of the GM's. The parts guys certainly don't have this info. Thanks Joel |
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Posted on: 2010/5/19 20:08
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1989 Coupe,L98 automatic |
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| Fluff | Re: Bore size of GM head gasket | ||
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Senior Guru
 
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Don't know if this is accurate:-
http://www.summitracing.com/parts/NAL ... NAL-12557236&autoview=sku It say's 4.000" / 101.600mm |
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Posted on: 2010/5/19 20:16
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93 LT1 Coupe. |
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| joeld | Re: Bore size of GM head gasket | ||
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Guru
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Yea Fluff, I've seen that. That's about all the info there is on this gasket.
Several months back I happened on some forum where there was a thread on this. Some guy was saying this gasket was actually 4.100. I might have to just buy one and measure! Thanks for the reply Joel |
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Posted on: 2010/5/19 23:51
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1989 Coupe,L98 automatic |
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| anesthes | Re: Bore size of GM head gasket | ||
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Master Guru
 
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Quote:
What is your reasoning behind going with a gasket that has the wrong bore, and has a .051" compressed thickness? Unless your piston is .015" sticking out of the hole, you don't want those gaskets. -- Joe |
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Posted on: 2010/5/20 12:05
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| joeld | Re: Bore size of GM head gasket | ||
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Hey Joe,
my concern is with the actual bore size of the GM gasket. With my engine being .040 over I was concerned about the fire ring being too close to the edge of the cylinder wall. I wasn't sure if the advertised specs on this gasket were a true 4.0 bore size or if in fact it was a little more to allow for any over bore engines. As far as the thickness, I'm not actually trying for the .51 thickness. This just happens to be what this gasket is. What I am trying to do is get the best sealing gasket for a simple street driven car. This gasket is the GM replacement for a alum head L98 and I was "leaning" towards using all GM gaskets. The piston is down in the hole. Could just go with Fel-Pro #1003 and get on with this. Any suggestions? Thanks for the reply Joel |
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Posted on: 2010/5/20 15:11
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1989 Coupe,L98 automatic |
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| anesthes | Re: Bore size of GM head gasket | ||
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Master Guru
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Quote:
1003, or a 1010 would be fine. Depending on the cam specs, and how performance oriented it was I might consider getting a gasket to dial the quench in right around .035, or .040 on the high side. If it's just a near stock street car, a 1003 or 1010 should be fine for a 355 with alum heads. -- Joe |
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Posted on: 2010/5/20 17:38
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