Tin Indian

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Head CC volume vs Compression Ratio:
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The below CR numbers are with the stock GM 5.7L displacement LS1 graphite head gaskets installed.

Installing the thicker 2003 GM MLS head gaskets will decrease your compression ratio by approx 0.1 - 0.2

72.27cc = 9.1 CR
71.71cc = 9.2 CR
71.05cc = 9.3 CR
70.59cc = 9.4 CR
70.03cc = 9.5 CR
69.74cc = 9.6 CR
68.91cc = 9.7 CR
68.35cc = 9.8 CR
67.79cc = 9.9 CR
67.23cc = 10.0 CR
66.67cc = 10.1 CR (stock LS1 head spec)
66.11cc = 10.2 CR
65.55cc = 10.3 CR
64.99cc = 10.4 CR
64.43cc = 10.5 CR (stock LS6 head spec)
63.87cc = 10.6 CR
63.31cc = 10.7 CR
62.75cc = 10.8 CR
62.19cc = 10.9 CR
61.63cc = 11.0 CR
61.07cc = 11.1 CR
60.51cc = 11.2 CR
59.95cc = 11.3 CR
59.39cc = 11.4 CR
58.83cc = 11.5 CR
58.27cc = 11.6 CR
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Inspector12

iTrader: (29)

Hey I am not an expert on the specs of heads by any means but I was under the impresion that the LS6 heads had a factory @ 71-72 cc combution chamber I am just wanting to know are you 100% about your information? I own a set and I would like to know for sure while trying to calculate my CR. Stock Z28 bottom end. Thanks!

Richard@WCCH

iTrader: (3)

Very helpful post.
All the LS6 heads I've cc'd have between 64.5-65.5cc. The 6.0l heads have 71-72cc chambers.

Richard

jrp

iTrader: (16)

so does this mean if you have 806 casting heads then you have 9.6 CR

Richard@WCCH

iTrader: (3)

It depends on head gasket thickness. Some production changes were made from year to year. For example, cars equipped with the 806 heads used composition head gaskets that compressed to approx. .040". While later cars used a .010" thicker MLS gasket. It only takes .005" to change 1cc with piston deck height or head gasket.
Hope this helps.

Richard

Gage

"it only takes .005" to change 1cc with piston deck height or head gasket."



does this mean that if my 5.3 heads are milled .015 then i now have a 58cc chamber ( i have 2.00/1.6 valves)

Tin Indian

Gage ... Just because you have 5.3 heads, does not mean your compression ratio will be the same as a stock unaltered 5.3 head.

Case in point: I have TEA 5.3 heads that were only milled .003" to insure straightness. But my heads were CCd at 63cc. When TEA ports the 5.3 head, the CNC machine removes material from the combustion chambers in order to unshroud the valves. This changes the chamber volume dramatically.

The only way you will know what your exact CR is ... Is to know exactly what the CC volume is in the chambers.

BTW, those numbers posted above are assuming stock 5.7L displacement, stock block deck height, stock pistons and stock GM graphite head gaskets.

Ron,

jrp

iTrader: (16)

ya, that helps, thanks

bigeller

iTrader: (2)

Interesting post.. I was just about to post a a question regarding this..

I have an LQ9 in my Z.. Is there anyway to do the Head CC volume vs Compression Ratio for the 6.0 HO engine.. The pistons are flat tops ala LS1.. The deck height is the same as an LS1.. The stroke is the same..Just a bigger bore.. The stock heads heads are 71.06cc..

I have a set of 70cc LS6 #243 casting heads with stock valve sizes that will go on soon, and I'm trying to figure out how much I could mill these heads with my TSP 228 228 .588 .588 cam straight up. I don't want the PV issues.. I know that with the stock #317 heads(71.06cc) the compression is 10.0:1.. I want to run between 10.8:1 - 11.0:1..

Thanks for the info.

Richard@WCCH

iTrader: (3)

Not quite. The crossectional area of the chamber is less than the diameter of the cylinder bore. For example, it takes about .005" milling of the block deck to remove 1cc of volume. It takes .007" milling to remove 1cc from an LS1 head. In THEORY you would lose a little over 2cc head volume, but as TinIndian pointed out, other factors can effect finished chamber sizes.

Richard

WicketMike

iTrader: (13)

whats the compression gonna be with the Patriot LQ9/LS6 heads like the ones Gomer has?

i ordered the same CC as gomer but dont remember and im still waiting to recieve them

gomer

iTrader: (13)

My chambers CC'd a little over 59cc, so that puts me right around 11.4 :1 comp ratio. That is where yours should be too.

WicketMike

iTrader: (13)

i thought the ratio was going to be closer to 11:1

we only have 91 octane here in california. you think i should mix that with some 103?

BigTex

iTrader: (16)

I come up with 10.8:1 using a stock head gasket and a non ported LS6 head.

Run the Felpro 1041 gasket and you'd have roughly 11.05:1 and a tighter squish area.

mykdiver

So the 6.0L heads are 71-72? I am trying to figure out the compression ratio for my new motor.

bigeller

iTrader: (2)

The 6.0L heads are approximately 71.06cc.

mykdiver

Thanks.

ssheets

iTrader: (1)

This is good, now let's turn the coin...

I'm looking at a cam swap and a friend of mine says' to shave the heads and bump up the CR while I'm at it!

On a stock 02 LS1what is safe? How much can I shave off without worrying about valve piston interference?

How much can I bump up the CR and still run on 91 octane pump gas without problems?

CAT3

iTrader: (9)

How far can you mill a set of 5.7l heads? I mean could I mill mine to say .040" or s that taking the surface too thin?

U LUZ

so how much would i have to shave off the ls6 head to put me up to 11.1 or 61.07ccs?