gonzo 6.2

iTrader: (8)

question for the pros
Take a LQ4 6.0 which is 9.4 compression,2 people from this forum,one being a sponser said "mill .020 off for 10.0" this I believe or a touch under 10,they also said if you bolt on a set of uncut LS6 heads (234s) "you will have 10.0 compression" This in my mind does not add up.This using stock 6.0 gasket.Thanks in advance for clearing it up.

jrp

iTrader: (16)

milling .020 off of a 6.0 head will put you at ~68cc. a stock ls6 (243) head has ~64cc chamber. obviously they cant both equal the same compression assuming everything else is equal.

are you sure you interpreted the sponsor correct?

gonzo 6.2

iTrader: (8)

I still have the PM,he writes "if I did my math right it would be 10.0"

I know the guy knows his stuff,he did us right on my buddys PKG.

gonzo 6.2

iTrader: (8)

Here it is cut and pasted and a little name edit.

Originally Posted by gonzo 6.0
Thanks


take a stock 6.0 LQ4 which is 9.4 stock compression.Bolt on a set of untouched LS6 heads,what comression would you have? I would imagine i would use OE 6.0 head gaskets. BTW the head and cam PKG. you did for my buddys 02 denali,well it flys,does everything we hoped for. thanks for that,my friend is very happy.




If my math is right you would be looking at around 10:1 comp ratio. Glad to hear that your buddy likes what we supplied. Did the pushrods we supplied work out? I remeber you having a concern about them. If there is anything else I can help you with just let me know.

BigTex

iTrader: (16)

I think he's off a couple of points either way. I get closer to 10.2:1 with LS6 heads on a stock gasket and 9.75:1 with a .020 milling.

gonzo 6.2

iTrader: (8)

See when he did my buddys heads he said if i take .020 you will end up at 10.0 What I asked for was 10.0,You and I have talked about this before,I feel it will be 10.5 or more with the Ls6 heads and stock headgaskets,but I am not for sure.

BigTex

iTrader: (16)

The chamber on a 6L head is just under 4". The total volume of a 4" wide cylinder .020" tall is basically 4cc. But you have to pull out the volume from the quench area. I estimated 75% of the chamber was open for the .020 mill, which would be 3cc. So chamber volume would drop from 71 to 68cc. Thats still 4cc more than the stock LS6 head.

BigTex

iTrader: (16)

Yes we have talked about it some. One other thing to think about with those stage II heads - the valves are larger and could take up some chamber volume. That could make the head volume in the 66cc range which would be right on 10:1.

64 cc chambers on a LQ4 using stock gaskets will put you around 10.2:1, but nowhere near 10.5:1.

Richard@WCCH

iTrader: (3)

As Jerami mentioned, milling .020" off of a 6.0l head brings the chamber size down to 68cc. That bumps compression to 9.70:1. A stock LS6 head measuning 64cc will bring the final c/r to 10.12:1.
Use caution when running c/r around the 10:1 range in heavy vehicles with pump gas as detonation becomes a problem. I see that some are able to get away with stock tunes running higher compression ratios than others.

Richard

gonzo 6.2

iTrader: (8)

Thanks to all.

NataSS Inc

iTrader: (9)

JUMPIN JESUS ON A POGO STICK!!!

I cant beleiveI never read this info before. According to the info listed my 58cc heads with the graphite gasket put my compression around 11.6:1 and maybe a tad higher than that.

When I first bought the heads I was told that compression would be at 10.8:1 so I wouldnt have to worry about detonation. Well over the course of time that I ran the heads I always had a bit of speckling on the plugs when I changed them. The ONLY time I didnt was when I did a 50/50 mix of 104 race gas.

That explains alot now............

CAT3

iTrader: (9)

Somewhat hard to tell which of these formulas works the best so here is my way of looking at it for a quick base line: Based of difference in a linear rate.
e.g. If a 66.67 chamber yields 10.2 and you mill .014" and nothing else is changed you go to a 64.45 chamber (.007" = 1cc for chamber shape) you have 10.5:1!
Pistons ordered for a 68cc chamber and .054 gasket yield 11.2:1 and swap head with a chamber of 5.3L 61.5 milled .010" (loss of 1.3cc based off shape of chamber roughly -.007= -1cc) and a gasket .042" (thats a loss -.012 at deck rate of about -.005=1cc, but we'll round it up to a loss, -2cc). -3cc from 61.5 = 58.5cc total, comparing the two chamber sizes, if 68cc = 11.2:1 then I am guessing my 58.5cc = 12.5:1 cr. Is this about right?

Spellbound

I would also like to know....

My 5.7 2.02 valved AS 2's cc'd at 62. I bought them used so I am assuming they were milled right around or a little more than .030?? When does intake alignment rear its ugly head?

Chevy99

With my stock block stock heads and stock gasket the CR is 10.2, can I only gange the gasket to get less CR without reprogramming? and which gasket?

Chevy99

Sorry, I want more CR not less.

Dave F

Tin Indian, you should edit your chart with more "know" heads. The GM racing LS6 head 88958622 is supposed to be around 60.9cc.

Also, it would be nice to have a chart of known gasket thickness. I have a set of Kometics which my GM racing contact said was the thinnest you could run without the piston coming too far out of the cylinder. I'll check the advertised compressed thickness in the shop later.

Z284U2TRY

iTrader: (5)

This a great thread for a compression beginner like me. I have a question was wondering if anyone in here wants to take a shot at it. If I have a engine set up for 67cc heads for a 11:1 compression. What would the compression be with a a stock ls1 head 66.67cc.? I am guessing the biggest variable would be the head gasket thickness when the piston was chosen.

Dave F

11.05. You would have 716cc of "piston" plus the 67cc of "head". Subtracting the .33cc from the "total" and the compressed volumes.

You're right, gasket will make a slight difference, but his is close enough. .33cc is pretty much nothing

fast98

iTrader: (16)

if i have 806 heads i have the 69cc chambers. so i am gunna put on the 241 heads 67cc chambers. if i use a .040 gasket that will put me at 10.6 ish?

DVCrazyCamTAWs6

iTrader: (6)

question, i have the 6.0L and running the Cup cam,and i want to put different untouched stock heads on it for a boost in compression wether it's the 5.3s ls1's or ls6's, but i cant bring the valve much closer to the piston or it will hit, what i've been trying to firgure and find out is wether changing the the heads to another set of stock heads off the ls1 or 5.3 brings the valve closer to the piston just like Modified Milled heads would do right?

so is it the chambers just different in design or have more material to acheive (higher compression / less CCs)

or is it that the ceiling of the chamber along with the valve closer to the face of the head which bring the also the valve closer to piston of at TDC

which is it ,, or am i completely off abour what i'm even trying to say

thanks