LS1 head combustion chamber CC volume vs CR

[Dave F]

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.

[bigeller]

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...

Originally Posted by jrp

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?

Originally Posted by gonzo 6.0

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.

[Moralesrx7]

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

[1999TransamWs6]

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?

[2CHEVYs]

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.

[blkmgc1]

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

[ssheets]

Originally Posted by ArKay99

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

[bluecamaroz28]

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?

[jhong321]

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

[Somebody09]

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

[speedz06]

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.

[speedz06]

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!

[mudracer]

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.

[98mysticZ]

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

[twogirls]

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. ??????????????????????

[chvycmaroz28]

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?

[LEEEPPS74]

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

[02silvaZ]

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

[Richard@WCCH]

Originally Posted by 02silvaZ

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

[03_SS_22]

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