Advanced Engineering Tech - LS1 head combustion chamber CC volume vs CR

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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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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!

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

Richard :)

Nice informative post. :nod:
Minor corrections, but still relevant:
Casting #933 '97 perimeter bolt 5.7l
Chambers = 69cc
Casting #806 '97-'98 perimeter bolt 5.7l
Chambers = 69cc
Casting #862 and 706 '99 and up 4.8-5.3l trucks
Chambers = 61cc

Richard :)

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

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

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 :)

"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)

"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)

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,

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 :)

ya, that helps, thanks :D

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.

"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)

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 :)

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

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


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.

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.


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?

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.

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.

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

The 6.0L heads are approximately 71.06cc.

The 6.0L heads are approximately 71.06cc.

Thanks.

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?

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?

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

Why am i hearing alot that a 72cc head will make a 9.5:1 comp ratio on a stock ls1 when the write up says 9.1:1 ?

Ok great info, now, how do we calculate that for a 427 with a 4.125 bore.

Thanks
Bryan

MYTURBO T/A - I was wondering the exact same thing. Everybody says a 317 casting 6.0 head will put you at 9.6 - 9.7 CR with the stock 71 cc chambers. That doesnt match up with that table very well. Which one is correct?

Justin

Many people have bolted on stock 6.0 heads and all of them report a 9.5-9.6 comp ratio so I trust that to be acurate.

Yes, I know this is my first post - I've just started reading these forums after buying an LS1 to put in my 71 Camaro. But I've got a lot of experience with the "old tech" motors :)

Just looking at the table at the beginning of this post, it seemed to me to exaggerate the sensitivity of CR to chamber volume. So I ran a quick calculation or two, using the basic formula I've always used to compute CR (lots of places to find this, the constants I use are from "Lingenfelter on modifying small block chevy engines"). The overall calculation is pretty straightforward:

CR = (SV + CV) / CV

where:

CR = compression ratio
SV = Swept Volume (displacement of one cylinder)
CV = Compressed Volume (volume at piston TDC)

To get the swept volume of one cylinder in CCs, the handy formula is:

bore x bore x stroke x 12.8704

For a stock short block, this works out:

3.90 x 3.90 x 3.62 x 12.8704 = 709 CC (rounded up)

Compressed volume is the sum of chamber volume, deck volume, gasket volume, and piston dish volume (including valve reliefs). For a stock LS1:

Chamber volume = 66.67
Deck volume = 3.9 x 3.9 x 12.8704 x (-.006) = -1.17 CC (negative because piston out of hole)

Gasket volume = 3.9 x 3.9 x 12.8704 x .060 = 11.7 CC (guessing on the gasket bore?)

Piston dish volume = 0 (true flat top piston)

Thus CV = 66.67 + 11.7 - 1.17 = 77.2 CC

Put all of this into the first formula:

CR = (709 + 77.2) / 77.2 = 10.18

Pretty close - my guess is that I've got gasket size slightly off, or that the factory is taking into account the piston/ring/wall volume, or something like that.

Anyway, the interesting thing is to run this with some different chamber volumes. Shrink the chamber by 8 CCs (to 58.67):

CR = (709 + 69.2) / 69.2 = 11.25

Expand the volume by 6 CCs (to 72.67):

CR = (709 + 83.2) / 83.2 = 9.5

So it seems to me that the table in this post does slightly exaggerate the changes in CR due to chamber volume. Or am I completely missing something?

Did you take into account that the Gen III motors have a negative deck height? About .008 I think. Also, depending on the type of GM gasket, compressed height is usually .054 or .060.

I did account for the piston out of hole - I used .006, based on some other posts I'd read. I used a .060 gasket thickness. Fiddling with those two parameters will increase or decrease the individual CR calculations slightly, but the point about relationship between CR and chamber volume remains ...

I think it would be beneficial to add to the original post that if you're using the later GM MLS gasket, that will decrease your compression by .1 - .2.

Craig

making this thread sticky again ;)

If this is going to be sticky again, the calculations should probably be redone (see my post above).

I just used Ross Piston's Calculator and can not get to 9:1 CR using the following data.
Bore 3.898
Stroke 3.622
Head Gasket .060
Deck Height -.008
Piston Dish .00
CC Volume 72
Cylinders 8

I get 9.6:1

How do you get 9:1 using stock gasket thickness and 72 cc head volume????????

If this is going to be sticky again, the calculations should probably be redone (see my post above).

Something definately not right here. I'll unsticky this again until resolved ;)

Using 3.898 bore, 3.622 stroke, -0.008 deck hight, 0.00 dish pistons, and 0.060 gasket thickness this is what i come up with...

9.1:1 = 77.27
9.2:1 = 76.21
9.3:1 = 75.16
9.4:1 = 74.15
9.5:1 = 73.16
9.6:1 = 72.19
9.7:1 = 71.24 (Approximate Combustion chamber of 6.0L heads +/-)
9.8:1 = 70.32
9.9:1 = 69.41
10.0:1 = 68.53
10.1:1 = 67.66
10.2:1 = 66.67 (Stock LS1 Head)
10.3:1 = 65.96
10.4:1 = 65.18
10.5:1 = 64.45 (Stock LS6 Head)
10.6:1 = 63.61
10.7:1 = 62.85
10.8:1 = 62.10
10.9:1 = 61.37 (Approximate Combustion chamber of 5.3L heads +/-)
11.0:1 = 60.66
11.1:1 = 59.96
11.2:1 = 59.27
11.3:1 = 58.60
11.4:1 = 57.93
11.5:1 = 57.28
11.6:1 = 56.65
11.7:1 = 56.02
11.8:1 = 55.41
11.9:1 = 54.81
12.0:1 = 54.20
15.4:1 = 38.00 (Stock C5R Head)

Although the stock ls1 compression figure may seem off, i have seen a lot of sites selling "stock ls1 long block" with a 10.2:1 compression ratio (i.e. pace performance). Perhaps 10.2:1 is the true compression ratio of a stock LS1 motor and GM says otherwise. GM has a nice way of making up their own horsepower and torque ratings for motors as they see fit, perhaps they figure 10:1 is just easier to say. The LS6 compression ratio seems right on according to the combustion chamber and the calculations. Since no one has ever been able to give a diffinitive answer on the actual size of a 6.0L combustion chambers (i've seen anywhere from 70cc-72cc) i think it is safe to assume that 6.0L heads would not lower a stock LS1/LS6 motor's compression ratio any more than 9.6:1.

If you notice on the original chart by the original thread starter, all combustion chamber sizes are exatly .56cc different per tenth from 9.1:1 to 11.6:1. That is obviously impossible. As the compression ratio increases, the combustion chamber does not decrease by equal incriments. A simple analogy would be swapping rear end gears without recalibrating your speedometer. If you swap from 3.42's to 4.11's your speedometer will read 15 miles per hour faster at 90mph and will read 5 miles per hour faster 20mph. It won't read a consistant increase/decrease across the board.

Hope this helps some people out. :cheers:

TTT

these calcs are w/0.00 dish pistons ... my pistons have 8cc reliefs cut in them... so could I just add 8cc to the Compress Volume?

Trying to figure out my CR ... 382 (3.898 bore, 4.000 stroke) using Felpro gaskets (so I heard they're .040" compressed?) w/unmilled TEA S2 5.3 heads (63cc chamber volume)

Felpro makes several LS1 gaskets. They have graphite and MLS I think. The 1041 MLS gasket has .043 compressed height and a 4.1" bore (from the package). Their stock replacement gasket probably has a stock compressed thickness of between .054 - .060".

TTT

these calcs are w/0.00 dish pistons ... my pistons have 8cc reliefs cut in them... so could I just add 8cc to the Compress Volume?

Trying to figure out my CR ... 382 (3.898 bore, 4.000 stroke) using Felpro gaskets (so I heard they're .040" compressed?) w/unmilled TEA S2 5.3 heads (63cc chamber volume)

With a 63cc combustion chamber, 3.898 bore, 4.000 stroke, -0.008 deck hight, -8cc dish pistons, and 0.040 gasket thickness i come up with 11.1:1

Stock 2002 MLS Crushed Head Gasket Thickness is .054 not .060

Guy's, are the MLS gasket's the later metal type? So if using these on a block that has the graphite gasket b4 you will loose .1 comp?

I just used Ross Piston's Calculator and can not get to 9:1 CR using the following data.
Bore 3.898
Stroke 3.622
Head Gasket .060
Deck Height -.008
Piston Dish .00
CC Volume 72
Cylinders 8

I get 9.6:1

How do you get 9:1 using stock gasket thickness and 72 cc head volume????????


You entered .060 when it would acturally be .052 This is what a stock head gasket is. With the same numbers you have and the different head gasket size the C/R comes out to 9.7:1, (this was with a .0008 deck height) still pretty close to where you were at. The only thing I could not do is add a negative .008 in the factor. The ross calculator dosen't allow a negative number in that spot. When using a .008 (instead of .0008) it come out to 9.55:1??????????????????????????

i believe my chambers are coming out around 68cc in my 5.7 heads.
if i use a stock graphite gaskit how much do i need to mill the heads
to get a 10.75 to 10.8-1 CR....anyone???

or is there a gasket i can use to get that CR ???????

test.

If you take the deck height and use a positive operator and make it +.005 and use .052 as the compressed gasket thickness everything seems to add up right for an LS1. If you use the Piston down bore of -.008 and a .060 head gasket, the LS6 CR is correct. As I see it there are basically 5 variables that need to be considered when computing compression ratio.

1: Head Chamber Volume. Stock is 66.67cc for an LS1 head and 64.43cc for an LS6 head.
2: The stock head gasket bore is 3.910"
3: The stock MLS gasket thickness is .060 compressed and the stock graphite gasket is .052" compressed. That gives a Head Gasket Volume of 11.81cc for an MLS gasket and 10.23cc for a graphite gasket.
4: Deck Volume which is Piston down bore @ TDC. Stock is -.008". That gives a deck volume os -1.57
5: Swept Cylinder Volume. The stock LS1 has a Bore of 3.900" and a stroke of 3.622" giving a Swept cylinder volume of 709.04cc

Adding up items 1-4 gives the Total Combustion Volume.
So, If I use the formula (Swept Cylinder Volume + Total Combustion Volume) / Total Combustion Volume = these results using a .060 MLS gasket:

72.27cc = 9.59 CR
71.71cc = 9.65 CR
71.05cc = 9.72 CR
70.59cc = 9.77 CR
70.03cc = 9.83 CR
69.74cc = 9.87 CR
68.91cc = 9.96 CR
68.35cc = 10.02 CR
67.79cc = 10.09 CR
67.23cc = 10.15 CR
66.67cc = 10.22 CR (stock LS1 head spec) ?
66.11cc = 10.29 CR
65.55cc = 10.36 CR
64.99cc = 10.42 CR
64.43cc = 10.50 CR (stock LS6 head spec)
63.87cc = 10.57 CR
63.31cc = 10.64 CR
62.75cc = 10.71 CR
62.19cc = 10.79 CR
61.63cc = 10.87 CR
61.07cc = 10.94 CR
60.51cc = 11.02 CR
59.95cc = 11.10 CR
59.39cc = 11.18 CR
58.83cc = 11.27 CR
58.27cc = 11.35 CR

using a .052 graphite gasket gives these results:
72.27cc = 9.76 CR
71.71cc = 9.82 CR
71.05cc = 9.90 CR
70.59cc = 9.95 CR
70.03cc = 10.01 CR
69.74cc = 10.04 CR
68.91cc = 10.14 CR
68.35cc = 10.21 CR
67.79cc = 10.27 CR
67.23cc = 10.34 CR
66.67cc = 10.41 CR (stock LS1 head spec) ?
66.11cc = 10.48 CR
65.55cc = 10.55 CR
64.99cc = 10.63 CR
64.43cc = 10.70 CR (stock LS6 head spec)
63.87cc = 10.78 CR
63.31cc = 10.85 CR
62.75cc = 10.93 CR
62.19cc = 11.01 CR
61.63cc = 11.09 CR
61.07cc = 11.17 CR
60.51cc = 11.25 CR
59.95cc = 11.33 CR
59.39cc = 11.42 CR
58.83cc = 11.51 CR
58.27cc = 11.59 CR

If the piston is shoved back into the head to +.005 Piston Down Bore that gives a deck volume of .98cc. If an MLS gasket is used with this parameter changed the results are as follows:

72.27cc = 9.34 CR
71.71cc = 9.39 CR
71.05cc = 9.46 CR
70.59cc = 9.50 CR
70.03cc = 9.56 CR
69.74cc = 9.59 CR
68.91cc = 9.68 CR
68.35cc = 9.74 CR
67.79cc = 9.80 CR
67.23cc = 9.86 CR
66.67cc = 9.92 CR (stock LS1 head spec)
66.11cc = 9.99 CR
65.55cc = 10.05 CR
64.99cc = 10.12 CR
64.43cc = 10.18 CR (stock LS6 head spec)
63.87cc = 10.25 CR
63.31cc = 10.32 CR
62.75cc = 10.39 CR
62.19cc = 10.46 CR
61.63cc = 10.53 CR
61.07cc = 10.60 CR
60.51cc = 10.67 CR
59.95cc = 10.75 CR
59.39cc = 10.82 CR
58.83cc = 10.90 CR
58.27cc = 10.98 CR

If the piston is shoved back into the head to +.005 Piston Down Bore that gives a deck volume of .98cc. If a graphite gasket is used with this parameter changed the results are as follows:

72.27cc = 9.49 CR
71.71cc = 9.55 CR
71.05cc = 9.62 CR
70.59cc = 9.67 CR
70.03cc = 9.73 CR
69.74cc = 9.76 CR
68.91cc = 9.85 CR
68.35cc = 9.91 CR
67.79cc = 9.98 CR
67.23cc = 10.04 CR
66.67cc = 10.10 CR (stock LS1 head spec)
66.11cc = 10.17 CR
65.55cc = 10.24 CR
64.99cc = 10.30 CR
64.43cc = 10.37 CR (stock LS6 head spec)
63.87cc = 10.44 CR
63.31cc = 10.51 CR
62.75cc = 10.59 CR
62.19cc = 10.66 CR
61.63cc = 10.73 CR
61.07cc = 10.81 CR
60.51cc = 10.89 CR
59.95cc = 10.96 CR
59.39cc = 11.04 CR
58.83cc = 11.12 CR
58.27cc = 11.20 CR

There are other factors that change CR but they are relatively minor compared to these variables. I am by no means discrediting the work done by Tin Indian or even contesting the published figures. I just took the tables and extrapolated them with different variables other than stock for cc volume and swept cylinder volume. What appears to me, if I am to justify GM's published CR specs for LS1 and LS6 engines are as follows. LS1 uses 66.67cc combustion chambers, .052 gasket thickness, and a Piston Down Bore @ TDC of +.005". An LS6 engine uses a combustion chamber of 64.43cc, .060 gasket thickness, and a Piston Down Bore @ TDC of -.008". Does this point to a design difference between the LS6 block and the LS1 block I am not aware of? It would be nice to know the spec for LS1 and LS6 deck volume. I personally have a 99 LS1 that is clearly and old-style LS1 block. Are my pistons sticking up out of the hole .008 or are the down the hole .005? This makes a huge difference is computed CR and it would be a great help to the guys changing heads and getting them shaved to know this.

Im about to have installed : west coast cyl heads casting #241 ls1 heads: ls1 stage 1+ ported. valve job 2.02/1.57 rev valves 5 angle cut. MILLED .030 chamber size 62cc compression ratio 10.8:1 or 10.9:1 new 918 springs ready to just bolt-on. The custom grind cam going in , is comp cam 228/228 .588/.588 114+2 Im worried about the p/v issues , but the installer and my ls1tuner has do this set-up to so many cars, and they say it will be fine, they are even running this set-up on one of my tuners cars. I thinking about ordering the cometic thicker head gaskets. Please advise on what i should do! Any advise on p/v issues will really help me quit worring! thanks jerry

You will be fine with that setup.. Will clear easily.

You will be fine with that setup.. Will clear easily.
thanks bigeller

heres one for you guys, if using a 6.0L block with 10.1 C/R with the stock 317 heads, if you bolted on stock LS1 heads, the C/R would go up correct ? any body got a number ?? The 317 heads have a 73cc chamber , and the LS1 heads have a 66cc chamber, so it WOULD go up right ??

That is a great question and the same one I had relative to my former setup.. I have a 10.1 Escalade engine.. The stock #317 heads are 71.06cc. I had a set of #243 LS6 castings that were bare initially, and were approximately 70cc.. I had them milled .020" Which should be something similar to the 66.67cc stock LS1 heads on a 3.898 bore..

The only accurate way to measure in my car would be to have the chambers cc'ed .. I would guess I was around 10.4:1..since the heads had been ported..

To answer your question.. Yes your compression ratio will increase.. I would guess you'd be at around 10.6:1..


heres one for you guys, if using a 6.0L block with 10.1 C/R with the stock 317 heads, if you bolted on stock LS1 heads, the C/R would go up correct ? any body got a number ?? The 317 heads have a 73cc chamber , and the LS1 heads have a 66cc chamber, so it WOULD go up right ??

anybody else got an answer ?? I have been doing research, and need to see if the block I have is an LQ4 or LQ9......I asummed that the iron block with alum heads had 10.0 to 1 C/R. but I have since read that the diff between the two are the pistons, if they are flat top pistons, it is 10.1:1, if they are dished pistons, it is more like 9.5:1 if anybody knows chime in

Sorry, I thought you already knew which engine you had when you said it was 10.1.. The blocks are the same between an LQ4 and an LQ9.. The LQ9 has flat tops and the LQ4 has dished pistons.. Mine is an LQ9 10.1 engine..

If you have an LQ4, which is the lower compression engine, you'll wanna put some LS1 or 4.8/5.3 truck castings on it to up the compression for an NA setup.

Your last sentence is correct.

anybody else got an answer ?? I have been doing research, and need to see if the block I have is an LQ4 or LQ9......I asummed that the iron block with alum heads had 10.0 to 1 C/R. but I have since read that the diff between the two are the pistons, if they are flat top pistons, it is 10.1:1, if they are dished pistons, it is more like 9.5:1 if anybody knows chime in

Up to what compression ratio can 93 octane handle well?

Damn u guys confused the hell out of me. So can someone help me with this question? I have a 98 block with stock internals. I want to put 6.0 heads on it because I have a set laying around. How can I get my compression ratio in the 10s? Can I get thicker head gaskets or do I have to get the heads shaved. Also I can get my hands on any rods, pistons, or crank from any new gen motor. Is there any they are the best to use?

Damn u guys confused the hell out of me. So can someone help me with this question? I have a 98 block with stock internals. I want to put 6.0 heads on it because I have a set laying around. How can I get my compression ratio in the 10s? Can I get thicker head gaskets or do I have to get the heads shaved. Also I can get my hands on any rods, pistons, or crank from any new gen motor. Is there any they are the best to use?

thicker gaskets decrease compression. exactly what CR are you trying to get "10's" is a broad number. if you can get the 02+ ls6 rotating assembly.

thicker gaskets decrease compression. exactly what CR are you trying to get "10's" is a broad number. if you can get the 02+ ls6 rotating assembly.I have a stock LS1 and I want to put 2001 and up 6.0 heads on it but I want my compression to be around 10.1. I was curious if 6.0 internals will work in an LS1?

I have a stock LS1 and I want to put 2001 and up 6.0 heads on it but I want my compression to be around 10.1. I was curious if 6.0 internals will work in an LS1?

milling the heads .030 will put you back at 10.1 w/ a stock gasket. and everything but the pistons (obviously) are interchangable.

So if I use a ls1 block I can put in 6.0 crank and rods and use LS1 or LS6 pistons Right? Do I have to get this line bored? and what would my cubs be?

So if I use a ls1 block I can put in 6.0 crank and rods and use LS1 or LS6 pistons Right? Do I have to get this line bored? and what would my cubs be?

your cubes will be stock; 3.90 bore x 3.622 stroke. and yes all internals sans pistons will fit. i'd say any machine work would be dependent on the condition of the block used.

http://ftp.scbbs.com/~al/lurk.gif

if i have a dome shape piston with 1.299 piston height with 59cc LS6 heads that yeild to 13.1 CR.. is there a formula that i can calculate the Cr .. i need to lower the Cr by getting a new heads with higher CC to 11.5:1..

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

Richard :)

Quick question: with the pre-LS1 SM engines, if the heads were milled (for whatever reason) the intake manifold surface also had to be milled a smaller amount to align the bolt holes and eliminate the gap between block and the front/rear of manifold. Does the geometry of the LS1 heads require the milling of the intake manifold surface if the block mating surface is milled?

TIA...JJ

I am going to go for approx 10.7-8 CR on a std bore / stroke LS1 block with the std graphite gaskest. What I'd like to know is what is the best after marlet cam for the LS1 to put it power wish a little beyond a std LS6? I beleive there is a GM part no for a cam past LS6 spec that comes with a softer set of springs in the kit as well. Does this sound right - any idea's what this no. is and what kind of power over std I could expect from the CR raise and the above cam and spring (nothing else planned - no porting) - maybe using later LS6 intake maniford.
Cheer Jon

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.

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.


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?

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.

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.

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.

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.

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.

http://z71.net/423/chamber.jpg

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.

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 :)

Thanks to all.

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............ :(

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?

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?


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?

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?

Sorry, I want more CR not less.

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.

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.

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

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?

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

I don't think there is any way to know other than to measure the clearance. Your head supplier might be able to answer your question, but I imagine you will need fly-cut pistons regardlsss. The cam you are running has a ton of overlap, which causes clearance issues while the valves are opening/closing, not while at max lift.

Scoggin Dickey sells a lot of these cams, and may know which heads will work untouched.

gonzo stated the 243 heads were uncut.. That is a big difference.. The uncut 243 heads are right around 70cc.. I had a set on my LQ9.. Scoggin Dickey sold them.. I had the uncut version of the GMPP ASA heads that had been CNCd.. Maybe that is what the guy was talking about.. Don't know...

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?


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.

408 cr #
flat top w/ 2cc valve relief
unmilled 806 5.7 heads 69cc
graphite gasket compressed .052
4.03 to 4.1 gasket bore
11.37 to 11.41 i might be off by a tenth at most
hope this helps the 408s questions
oh with a gasket bore of 4.1 and compressed to .040 cr = 11.72 /
gasket bore of 4.03 compressed to .040 cr = 11.77 :drive:

Can the AFR 72cc 225cc heads be milled enough for 11:1 CR with .041 gasket and with 231.8/237.1 .589/.598 on a 111.9 LSA without having a piston to vlalve cleaarance issue? If so how much to mill?

I have a 4.8L i am putting a set of ls1 heads on i used a compression calculator to find out absalutly nothing. so i ask for help here.

Bore 96mm/3.780
stroke 83mm/3.268
gasket .054
piston cc i dont know
I am looking to get a 10.5-8 to 1 CR, i am assuming i will need to mill the heads to 58cc can ls1 heads be milled that much and how much is that to make a 66cc to 58cc that is an 8cc differance 8x.007=.056 right.

My cam is 220/220 .581/.581 willl i clear ok.

I dont know if im even close help please.

don't think you'll have a problem but get another opinion to be safe

If you take the deck height and use a positive operator and make it +.005 and use .052 as the compressed gasket thickness everything seems to add up right for an LS1. If you use the Piston down bore of -.008 and a .060 head gasket, the LS6 CR is correct. As I see it there are basically 5 variables that need to be considered when computing compression ratio.

1: Head Chamber Volume. Stock is 66.67cc for an LS1 head and 64.43cc for an LS6 head.
2: The stock head gasket bore is 3.910"
3: The stock MLS gasket thickness is .060 compressed and the stock graphite gasket is .052" compressed. That gives a Head Gasket Volume of 11.81cc for an MLS gasket and 10.23cc for a graphite gasket.
4: Deck Volume which is Piston down bore @ TDC. Stock is -.008". That gives a deck volume os -1.57
5: Swept Cylinder Volume. The stock LS1 has a Bore of 3.900" and a stroke of 3.622" giving a Swept cylinder volume of 709.04cc

Adding up items 1-4 gives the Total Combustion Volume.
So, If I use the formula (Swept Cylinder Volume + Total Combustion Volume) / Total Combustion Volume = these results using a .060 MLS gasket:

72.27cc = 9.59 CR
71.71cc = 9.65 CR
71.05cc = 9.72 CR
70.59cc = 9.77 CR
70.03cc = 9.83 CR
69.74cc = 9.87 CR
68.91cc = 9.96 CR
68.35cc = 10.02 CR
67.79cc = 10.09 CR
67.23cc = 10.15 CR
66.67cc = 10.22 CR (stock LS1 head spec) ?
66.11cc = 10.29 CR
65.55cc = 10.36 CR
64.99cc = 10.42 CR
64.43cc = 10.50 CR (stock LS6 head spec)
63.87cc = 10.57 CR
63.31cc = 10.64 CR
62.75cc = 10.71 CR
62.19cc = 10.79 CR
61.63cc = 10.87 CR
61.07cc = 10.94 CR
60.51cc = 11.02 CR
59.95cc = 11.10 CR
59.39cc = 11.18 CR
58.83cc = 11.27 CR
58.27cc = 11.35 CR

using a .052 graphite gasket gives these results:
72.27cc = 9.76 CR
71.71cc = 9.82 CR
71.05cc = 9.90 CR
70.59cc = 9.95 CR
70.03cc = 10.01 CR
69.74cc = 10.04 CR
68.91cc = 10.14 CR
68.35cc = 10.21 CR
67.79cc = 10.27 CR
67.23cc = 10.34 CR
66.67cc = 10.41 CR (stock LS1 head spec) ?
66.11cc = 10.48 CR
65.55cc = 10.55 CR
64.99cc = 10.63 CR
64.43cc = 10.70 CR (stock LS6 head spec)
63.87cc = 10.78 CR
63.31cc = 10.85 CR
62.75cc = 10.93 CR
62.19cc = 11.01 CR <<<I want to be here
61.63cc = 11.09 CR
61.07cc = 11.17 CR
60.51cc = 11.25 CR
59.95cc = 11.33 CR
59.39cc = 11.42 CR
58.83cc = 11.51 CR
58.27cc = 11.59 CR

If the piston is shoved back into the head to +.005 Piston Down Bore that gives a deck volume of .98cc. If an MLS gasket is used with this parameter changed the results are as follows:

72.27cc = 9.34 CR
71.71cc = 9.39 CR
71.05cc = 9.46 CR
70.59cc = 9.50 CR
70.03cc = 9.56 CR
69.74cc = 9.59 CR
68.91cc = 9.68 CR
68.35cc = 9.74 CR
67.79cc = 9.80 CR
67.23cc = 9.86 CR
66.67cc = 9.92 CR (stock LS1 head spec)
66.11cc = 9.99 CR
65.55cc = 10.05 CR
64.99cc = 10.12 CR
64.43cc = 10.18 CR (stock LS6 head spec)
63.87cc = 10.25 CR
63.31cc = 10.32 CR
62.75cc = 10.39 CR
62.19cc = 10.46 CR
61.63cc = 10.53 CR
61.07cc = 10.60 CR
60.51cc = 10.67 CR
59.95cc = 10.75 CR
59.39cc = 10.82 CR
58.83cc = 10.90 CR
58.27cc = 10.98 CR

If the piston is shoved back into the head to +.005 Piston Down Bore that gives a deck volume of .98cc. If a graphite gasket is used with this parameter changed the results are as follows:

72.27cc = 9.49 CR
71.71cc = 9.55 CR
71.05cc = 9.62 CR
70.59cc = 9.67 CR
70.03cc = 9.73 CR
69.74cc = 9.76 CR
68.91cc = 9.85 CR
68.35cc = 9.91 CR
67.79cc = 9.98 CR
67.23cc = 10.04 CR
66.67cc = 10.10 CR (stock LS1 head spec)
66.11cc = 10.17 CR
65.55cc = 10.24 CR
64.99cc = 10.30 CR
64.43cc = 10.37 CR (stock LS6 head spec)
63.87cc = 10.44 CR
63.31cc = 10.51 CR
62.75cc = 10.59 CR
62.19cc = 10.66 CR
61.63cc = 10.73 CR
61.07cc = 10.81 CR
60.51cc = 10.89 CR
59.95cc = 10.96 CR
59.39cc = 11.04 CR
58.83cc = 11.12 CR
58.27cc = 11.20 CR

There are other factors that change CR but they are relatively minor compared to these variables. I am by no means discrediting the work done by Tin Indian or even contesting the published figures. I just took the tables and extrapolated them with different variables other than stock for cc volume and swept cylinder volume. What appears to me, if I am to justify GM's published CR specs for LS1 and LS6 engines are as follows. LS1 uses 66.67cc combustion chambers, .052 gasket thickness, and a Piston Down Bore @ TDC of +.005". An LS6 engine uses a combustion chamber of 64.43cc, .060 gasket thickness, and a Piston Down Bore @ TDC of -.008". Does this point to a design difference between the LS6 block and the LS1 block I am not aware of? It would be nice to know the spec for LS1 and LS6 deck volume. I personally have a 99 LS1 that is clearly and old-style LS1 block. Are my pistons sticking up out of the hole .008 or are the down the hole .005? This makes a huge difference is computed CR and it would be a great help to the guys changing heads and getting them shaved to know this.

Somebody prove me right or wrong. I've got a stock 02 LS1 bottom end, pistons etc. I'm swapping heads using a set of 5.3's. Our desired CR is 11:1 + So using a stock MLS .052" gasket we should chamber the heads to be 62.19ccs.

Would I be better going for a tighter quinch and using a .042" gasket and going for 62.29cc Chambers?

Or how about staying with 62.19cc and measuring PtoV prior to install and if I can run the .042" and have a slightly higher CR?

I'll be installing an F14 cam and the heads have 2.02" intakes so I'll be measuring PtoV regardless:devil:

What will be the CR with bone stock 5.3L heads on a 6.0L LQ4 engine?

Will the 5.3L heads require some work to fit on the 6.0L engine specially that 6.0L has bigger bore size?

How far will the piston be from the valve with stock cam?

Hello All
I am new to the ls1 motors I just bought a 2000 frc and it has stage 2 Heads (thats all i know about the heads) , TR 224 114 cam .Well about 3 weeks ago the motor needs to be change (pullie fell off and grinded up the crankshaft) I went out and got a SDPC 402 motor with a -15cc dish piston and 226/226 lsa112 cam. I will be useing the old ls1 heads that are stage2. It looks like the heads where milled how much? I don't know. How will i find out if this combo will work? What is the max a head can be milled? I am worried that i might have to much or not enough CR .

Thanks for your input

Just to clarify... if I have stock everything and get -4cc dished pistons, it'll be 66.67cc (stock) + 4cc (piston) = 70.67cc total and about 9.67 CR?

I'm trying to get down to 9.0:1 CR with just my pistons.

Thanks,
somebody

I think that although the combustion chamber size plays a main role in the compression ratio,there may be some differences in pistons from year or model of engine.Like the ls6 heads might increase comp ratio more or less on a 5.3 than a ls1 or lq4/lq9,is this true?also--SOMEBODY,you said you wanted to use pistons to decrease CR the larger chambers in the LQ9 help them breathe better cause the valves are unshrouded.Now you have me thinking about the best way to lower compression--pistons or combustion chamber cc increase?also,calculate actual compression when your done building.At Bill Mitchel racing engines I used to check compression with a whistler we bought from Katech.The thing used frequency resonance to calculate actual CR and it was pretty cool way to check it out.good luck with your build. :gay:

greetings Jhong,why did you buy (I presume a shortblock,and you want to use the heads from your old motor)15cc dished pistons?If the sales guy on the phone suggested he must have a reason.What CR did he say you would get with the heads you have(what heads do you have?)Also stage 2 heads could mean anything,it depends whos heads they are they may not even be milled.also,If you have some miles on the engine,go ahead and change the valvesprings they are a wear part.Also you can be sure that you get the springs recommended for your new cam in the new engine.TI retainers would be nice too.those dished pistons may also allow you to use 1.85:1 rockers.Go for forged so you have the option later to use forced induction.I know I'm going on but you asked for some input!

Curiously, as I read through this thread, i only found one mention of quench.

As my first post here, please dont be offended when I ask this question. I too am searching for information.

Is quench distance as big an issue with the LSx engines as it was with the older small blocks? or does the computer allow less detonation?

I dont know much about these engines, guys, but I need to learn. I have a couple to build. I was under the assumption that with an old style small block chevy, you have to keep your quench height to between .040 and .055 to keep the engine out of basic detonation under normal operating conditions.

I just didnt know if the same was true for the LSx engines.

Anyone?

I can see the new chamber shape and the help it may give to this engine. I hadnt heard much about a piston being out of the cylinder being beneficial towards building more power.

ok so i got a set of heads ls1 241's and were milled to a 61.ish cc buying used... so whats a guess on how much they were milled... and how much longer will i have to go on a push rod if i used the stock gaskets..... soon to be a 408 with a ms4

I am building a 6.0liter out of a 2003 1500HD truck for a 1956 chevy truck I am restoring and I need some serious help. I would like to make around 400hp with this motor, but what would be suggested to do this. I would like to put a cam in it and a different set of heads but really dont know what to use at this point. Someone please point me in the right direction. I also have a 5.3liter out of a 2001 suburban that I can build as well if there is any benefit to do that. ??????????????????????

if i have a stock ls1 with 10.1 CR and get 205cc or 225cc heads with 63cc conbustion chambers it will raise to CR to 10.7? is higher compression gunna mean more power?

You Can Mill Ls1 Stock Heads To .060 , But Must Have Racing Gas112

what is safest highest compression ratio on 93 octane pump gas?

what is safest highest compression ratio on 93 octane pump gas?

Unfortunately this is not a cut and dried answer. Choosing a final compression ratio depends on working cylinder pressures and engine load. I also take climate into consideration when recommending target compression ratios. Here's some of the criteria I use when considering compression. I've listed them in order of importance.
1) Engine displacement
2) Vehicle weight (car, truck, boat, motorcycle,etc.)
3) Camshaft grind (controls cylinder pressures)
4) Transmission type (automatics tend to increase engine load)
5) Rear gear ratio
6) Rear tire diameter
7) Maximum summer temps

As you can see there are a number of things that can influence your final compression ratio decision.

Good luck,


Richard :)

so can i boost the compression with p&p 6.0 lq9 heads? I am going 408. These are my stockers.

I have a 2005 LM7 5.3 out of a 05 Silverado. I'm going to turbo the car. I believe the CR is 9.5 to 1 with a 62 cc head. What would the CR be with a 72 cc lq9 head?

Bring it back from the death. I've been reading whole 6 pages and kinda confused.

1) There's at least 3 different CR rating table base on almost the same varible, which one is acurate?
2) I read some post that 68cc will yield 11.2:1 and 58.5cc will yield 12.5:1. How is that possible according to all 3 table listed above?
3) There's different posts stated different chamber volume on a stock untouch LS6 head, from 64.XXcc to 70.XXcc? How's that possible with 6cc difference?
4) Different head gasket height will affect final CR, but how can a change of 0.060 to 0.054 head gasket yield more than 0.1 CR change according some post?

I just named a few here. I'm not a guru or anything so I could be missing something. I'm trying to find out more info for my stock bottom end LS1 build, now I'm lost. Someone please clarify and Mod please make necessary post edit so newbie like me won't mix up.