LS1 head combustion chamber CC volume vs CR
05-03-2009, 05:22 AM
#102
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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.
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.
07-08-2009, 11:16 AM
#103
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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.
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.
Why did GM rate the CR of the LS1 at 10.1:1 instead of 10.2:1 if this is correct.?
02-21-2013, 09:41 PM
#106
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well i thought id bring this one back form the dead too lol
however im trying to lower my Cr a bit for boost. now i have an interesting question about stock 5.7L and using 317 heads with slightly thinner gaskets form commetics
i used this calculator to get these combonations and thought it was interesting
http://www.csgnetwork.com/compcalc.html
i im putted using 71.24cc for the 317 heads as im guessing reading through most of these that thats it that but i also come across 72 so im not sure, but to be safe and not have more CR then i think ill have ill use the smaller chamber to get the calculations
(of course if 72 is used these will go down but very slightly if even noticable)
bore - 3.989
stroke -3.622
gasket bore - 4.010
gasket thickness - .040
CC in cc's - 71.24
deck clearnance - -0.007 (out of bore)
CR = 10.06:1
with only changing gasket thickness data
.045 = 9.94:1
.048 = 9.82:1 (LS9 gasket dimentions used)
.050 = 9.82:1
.051 = 9.80:1
.055 = 9.71:1
.058 = 9.65:1
now im wondering, would using a .045 cometics gasket be ok to run with 317 heads on an ls1? (everything stock minus maybe a mild cam no bigger then 230 ranged) i would really like to run it with that sized gasket if its possible. i was thinking the .040 but i think that might be higher then what i want. but if the stock ls1 is closer to 10.2:1, then knocking it down to 10:1 or 9.9 range wouldnt be that bad on mild boost with the right tuning id image.
however im trying to lower my Cr a bit for boost. now i have an interesting question about stock 5.7L and using 317 heads with slightly thinner gaskets form commetics
i used this calculator to get these combonations and thought it was interesting
http://www.csgnetwork.com/compcalc.html
i im putted using 71.24cc for the 317 heads as im guessing reading through most of these that thats it that but i also come across 72 so im not sure, but to be safe and not have more CR then i think ill have ill use the smaller chamber to get the calculations
(of course if 72 is used these will go down but very slightly if even noticable)
bore - 3.989
stroke -3.622
gasket bore - 4.010
gasket thickness - .040
CC in cc's - 71.24
deck clearnance - -0.007 (out of bore)
CR = 10.06:1
with only changing gasket thickness data
.045 = 9.94:1
.048 = 9.82:1 (LS9 gasket dimentions used)
.050 = 9.82:1
.051 = 9.80:1
.055 = 9.71:1
.058 = 9.65:1
now im wondering, would using a .045 cometics gasket be ok to run with 317 heads on an ls1? (everything stock minus maybe a mild cam no bigger then 230 ranged) i would really like to run it with that sized gasket if its possible. i was thinking the .040 but i think that might be higher then what i want. but if the stock ls1 is closer to 10.2:1, then knocking it down to 10:1 or 9.9 range wouldnt be that bad on mild boost with the right tuning id image.
Last edited by JoshuaGrooms83; 02-21-2013 at 10:36 PM.
01-22-2014, 02:08 PM
#107
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I have a Tick Polluter cam 242/244 112LSA & I'm installing some ported/polished 243 heads & was going to have them milled also. Was wondering if you could recommend how much I should have them milled? Thanks
