Comp. ratio consufion..

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Oct 12, 2005 | 11:35 PM

VTC_WS6

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From: Austin, Tx

Comp. ratio consufion..

From what I've read to date, the LQ9 6-liter has a stock compression of 10.0:1 with it's 71cc heads, now obviously if I were to find an LQ9 and swap on a set of 64cc LS6 heads I'm looking at a bump in compression, my question is exactly how much compression would I be looking at?

As a side note, I noticed the book I've read is telling me the LQ4 and LQ9, although both 6-liters, are infact different in displacement (364cu. in vs. 377cu. in), can anyone tell me where this comes from? All the info I can find tells me they both have 99mm cranks to I'm guessing it's the bore (duh), anybody know the numbers?

Thanks

Oct 13, 2005 | 12:26 AM

Chevy_Truck_Man

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From: Cumming, Ga

The blocks are the same, they have the same displacement, but some how the LQ9 gets more compression which explain the higher displacement number. I'm not quite sure where the compression comes from because they both have basically the same heads, crank, pistons, and rods.

The LQ9 possibly has a slightly different crank and heavier, stronger, slightly different shaped rods. It has the same pistons but they're coated with some crap to do somthing

I found this link a while ago on another post... very helpful

http://www.automotiverebuilder.com/ar/eb040538.htm

Last edited by Chevy_Truck_Man; Oct 13, 2005 at 12:38 AM.

Oct 13, 2005 | 01:02 AM

JZ'sTA

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From: Ft. Myers Fl

Acturally if the WS6 you have in the sig is a 5.7 motor then a LQ9 head will be closer to 9.3:1
A 64 cc head and .040 gasket and take you up to 11:1
Check out my sig.

Oct 14, 2005 | 11:49 PM

VTC_WS6

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From: Austin, Tx

Quote:

Originally Posted by JZ'sTA

Acturally if the WS6 you have in the sig is a 5.7 motor then a LQ9 head will be closer to 9.3:1
A 64 cc head and .040 gasket and take you up to 11:1
Check out my sig.

Yea it is, but I was talking about using an LQ9 bottom end since mine evidently spun a bearing.

Oct 15, 2005 | 01:00 AM

jhong321

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From: bayarea

Quote:

Originally Posted by VTC_WS6

i show you compression at 10:9.1 if you stay with the standard gasgets

Oct 15, 2005 | 01:16 AM

jrp

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From: Valencia, Ca

Quote:

Originally Posted by Chevy_Truck_Man

there is some incorrect info in that link. all 6.0l wether it be lq9, lq4, or ls2 use a 4.00 bore and 3.898 stroke for 364 displacement. the pistons in the lq4 are dished approximatey 8.6cc, that accounts for the .7 compression difference from the lq9 as they've both got the same 71-72cc head volume.

and i get the same CR as jhong.

Last edited by jrp; Oct 15, 2005 at 01:23 AM.

Oct 15, 2005 | 01:22 AM

jrp

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From: Valencia, Ca

Quote:

Originally Posted by JZ'sTA

Acturally if the WS6 you have in the sig is a 5.7 motor then a LQ9 head will be closer to 9.3:1
A 64 cc head and .040 gasket and take you up to 11:1
Check out my sig.

what are you using for gasket thickness and deckheight. i come up with ~9.7 with a 5.7 MLS gasket and stock deck height. hell, couldnt even come up with anything lower then 9.5 using a .060 gasket and 0 deck, and we both know that the pistons are above the deck.