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LS3 head chamber cc

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Old 08-13-2010, 11:43 PM   #1
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Default LS3 head chamber cc

Does anyone know for sure what the combustion chamber size is for the LS3/L92 head? Some publications say 70cc and others say 68cc. Also does any body know for sure how much I need to mill the head to get a 65cc chamber? I have read .025 and also read .030. Is the "rule of thumb" .006 per 1cc? I'm putting my LS3 heads on my LQ9 6.0 and I want to run 10.9 compression , same as LS2. thanks
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Old 08-14-2010, 12:55 AM   #2
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Does anyone know for sure what the combustion chamber size is for the LS3/L92 head? Some publications say 70cc and others say 68cc. Also does any body know for sure how much I need to mill the head to get a 65cc chamber? I have read .025 and also read .030. Is the "rule of thumb" .006 per 1cc?
68cc is factory LS3/L92 chamber size

.006" per cc
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Old 08-14-2010, 01:16 AM   #3
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sorry bud dont mean to jack your thread here just curious,how much can you safely mill off of these heads? i have -12cc pistons with untouched 821s and the power just isnt there, thinkin of millin this winter. would like to get to 11.1-11.5.1 can this be done with milled heads and a thinner gasket than what im using now?(.051)
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Old 08-14-2010, 01:51 AM   #4
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I remember reading they are 68cc chambers
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Old 08-15-2010, 09:23 AM   #5
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weird they had to take .014 off my ls3 heads to get 68cc
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Old 08-16-2010, 10:10 PM   #6
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Default chamber size

Most reports I've seen says 70cc, and to get to 68cc you need to mill .012, and for 65cc you need to mill.030. I guess when I take my heads to the machine shop I'll get them to measure the cc first, then mill them .012 and measure again, then mill .018 more (.030 total) and measure again, then we will know for sure.
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Old 08-17-2010, 05:27 AM   #7
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The factory blueprints show 68.4cc +-1 cc for the L92 heads. Mine came in at 68 cc in stock form.
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Old 08-29-2010, 12:59 AM   #8
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I took my ls3 heads to my machine shop friday to have them cc'd then milled and cc'd again, should have them back in a few days and will post the results.
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Old 08-29-2010, 09:31 AM   #9
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Stock is 68cc give or take 1cc. A good porter can mill them .020-.030, sink the valves a tad and you'll still have some decent PTV clearance.

FWIW, I've done a 223/235 115 on LS3 castings cut .030. Had .060 intake clearance and .080'ish exhaust. Runs good.

Last edited by Damian; 09-05-2010 at 12:49 AM.
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Old 08-29-2010, 05:15 PM   #10
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Stock is 68cc give or take 1cc. A good porter cam milled them .020-.030, sink the valves a tad and you'll still have some decent PTV clearance.

FWIW, I've done a 223/235 115 on LS3 castings cut .030. Had .060 intake clearance and .080'ish exhaust. Runs good.
Cuttin it close I see....

duals or behive springs?

Looks like the LSL lobes
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Old 09-04-2010, 10:12 PM   #11
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Default chamber cc

Ok, I got my heads back from the machine shop, stock chamber size was 68.5 cc, they then milled them .030 and the chamber size is now 63cc., stock LS2 has 64.5 cc heads and flat tops and 10.9 compression, my engine should come in about 11.1:1 compression ratio, engine is LQ9 6.0, flat tops. thanks for all the input guys,
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Old 09-05-2010, 12:50 AM   #12
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Cuttin it close I see....

duals or behive springs?

Looks like the LSL lobes
Close is fine if you've got a light weight valve and good spring. In that type of scenario I'll run them .050-.060 clearance on the intake without any worries. Those springs were "PSI" springs. Single beehive and will hold .650 all day.

It is LSL lobes. Those lobes work real well with the LS3/L92 heads.
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Old 09-05-2010, 01:07 AM   #13
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Is there any worry about intake port seal cutting so much off the head?
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Old 09-05-2010, 06:17 AM   #14
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Is there any worry about intake port seal cutting so much off the head?
No, milling .030 off will not cause intake to head sealing issues.

Last edited by 69LT1Bird; 09-05-2010 at 06:27 AM.
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Old 09-05-2010, 10:52 AM   #15
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Close is fine if you've got a light weight valve and good spring. In that type of scenario I'll run them .050-.060 clearance on the intake without any worries. Those springs were "PSI" springs. Single beehive and will hold .650 all day.

It is LSL lobes. Those lobes work real well with the LS3/L92 heads.
Cool, what kind of power did that combo put down?
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Old 09-05-2010, 11:56 AM   #16
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Cool, what kind of power did that combo put down?
Not sure. We don't dyno too many cars @ my shop. They're built/tuned to be fast on the street, not the dyno.
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Old 09-06-2010, 08:58 AM   #17
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So wouldn't you better off to try a thinner cometic gasket first instead of milling? That way if your cam doesn't fit no harm done, afterall you cant un-mill your head.
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Old 01-19-2014, 06:09 AM   #18
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Originally Posted by richardp View Post
Ok, I got my heads back from the machine shop, stock chamber size was 68.5 cc, they then milled them .030 and the chamber size is now 63cc., stock LS2 has 64.5 cc heads and flat tops and 10.9 compression, my engine should come in about 11.1:1 compression ratio, engine is LQ9 6.0, flat tops. thanks for all the input guys,
sounds good, I get 10.8 - 11.2 SCR depending on your piston to deck height.
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