Am I safe with a Cometic .040 headgasket
07-11-2006, 10:18 PM
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Am I safe with a Cometic .040 headgasket I am about to embark on a head cam job on my T/A, I have AFR 205's cut .018 to 63 cc, and a stock 346 shortblock. My cam is a Stealth2 224-220 581-581 lift cut on a 116degree. I want to use the .040 cometics so I can benifit from better quench over the GM MLS gaskets that are .052. My pistons are not flycut so my concern is obviously PTV clearence. I have not done a DCR with either combo yet. Thanks in advance.
07-11-2006, 10:28 PM
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Originally Posted by Ramairbird
I am about to embark on a head cam job on my T/A, I have AFR 205's cut .018 to 63 cc, and a stock 346 shortblock. My cam is a Stealth2 224-220 581-581 lift cut on a 116degree. I want to use the .040 cometics so I can benifit from better quench over the GM MLS gaskets that are .052. My pistons are not flycut so my concern is obviously PTV clearence. I have not done a DCR with either combo yet. Thanks in advance.
Your pistons come .006-.007" out of the hole...
If you go with a .045" you will have a quench of .038-.039"
Can't find a .045" thick cometic? Take a look at TSP
07-12-2006, 12:10 AM
#3
Actually the best quench is around .032, you're a little high on that one. Ask a lot of people who are running aftermarket shortblocks with the pistons .008 out of the hole, most are running .040 cometics for the .032 quench, including myself.
07-12-2006, 07:11 AM
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Originally Posted by ArcticZ28
Actually the best quench is around .032, you're a little high on that one. Ask a lot of people who are running aftermarket shortblocks with the pistons .008 out of the hole, most are running .040 cometics for the .032 quench, including myself.
07-12-2006, 07:51 AM
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Originally Posted by slow trap
.032 is what i will have also,hopefully these cometics will seal.i'll also have around 11:9 cr,8.7dcr.
FWIW I am running the .040 Cometics no problems
07-12-2006, 07:52 AM
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Originally Posted by slow trap
.032 is what i will have also,hopefully these cometics will seal.i'll also have around 11:9 cr,8.7dcr.
Should have a 12.3 SCR and a 8.75 DCR. Pretty close to what you have
07-12-2006, 09:16 AM
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Well, I thought my pistons would be .008" out of the hole, but when I had the heads off they were .004" out of the hole. I don't think you can make a general assumption that the pistons will be out this much or that much. You need to measure. However, I am using those gaskets and make pretty good power, running, ~11.3:1 CR, ~8..78:1 DCR, notched pistons, 93 octane, and only seldom have about 1-2 degrees kr. 1/2 can of Torco fixes that every time and it's usually only on really hot days.
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07-12-2006, 10:00 AM
#8
Most of the top engine builders on the site (HPE, FFHP, etc) put the pistons .008 out of the hole which is why I said aftermarket shortblocks. It's a pretty safe assumption at this point in the game unless the customer specifically asks for a different setup.
07-12-2006, 10:07 AM
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I have mine .010 out and with 6.0 MLS I have .040 quench (370).
But TTT, you will not have any issues with PTV.
But TTT, you will not have any issues with PTV.
Last edited by PREDATOR-Z; 07-13-2006 at 07:30 AM. Reason: TYPO
07-12-2006, 03:10 PM
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Originally Posted by ArcticZ28
Most of the top engine builders on the site (HPE, FFHP, etc) put the pistons .008 out of the hole which is why I said aftermarket shortblocks. It's a pretty safe assumption at this point in the game unless the customer specifically asks for a different setup.
07-13-2006, 08:33 AM
#17
I have a similar question, and instead of starting a new post, I figured I'd hijack this thread.
I am in a similar situation with where I want to run a tighter head gasket to get a better quench since I'm currently running the non-mls gm gasket which is 0.056" compressed (at least that's what I've read).
I know my heads were milled 0.030" but I'm running the TR 224/224 on a 112lsa and I heard it has an additional amount of advance ground in??? I'm not sure how that will affect PtoV, but I've heard other people say I'll be fine, but it never hurts to get more educated opinnions and advice.
I am in a similar situation with where I want to run a tighter head gasket to get a better quench since I'm currently running the non-mls gm gasket which is 0.056" compressed (at least that's what I've read).
I know my heads were milled 0.030" but I'm running the TR 224/224 on a 112lsa and I heard it has an additional amount of advance ground in??? I'm not sure how that will affect PtoV, but I've heard other people say I'll be fine, but it never hurts to get more educated opinnions and advice.
