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Are my compression figures right?

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Old Feb 17, 2008 | 01:37 PM
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Default Are my compression figures right?
2002 stock LS1:

PRC 5.3 2.5 heads
62cc combustion chamber
.40 cometic gaskets
TR 224 112+4 cam

If I were to do these mods I come up with SCR of 11.346 & DCR of 8.695. Anyone tell me if these figures are right, if not can someone correct them?
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Old Feb 17, 2008 | 01:39 PM
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Is that an aftermarket hood on the car. Looks good.
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Old Feb 17, 2008 | 06:09 PM
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No, it's a stock firehawk hood
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Old Feb 17, 2008 | 06:40 PM
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Old Feb 17, 2008 | 07:21 PM
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TSP figured mine up to be 10.88 to one with the stock CC 5.3 heads and .030 cometic gaskets, i dont know if haveing 4cc valve releifs affect it or not.
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Old Feb 17, 2008 | 09:56 PM
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Originally Posted by jow02327
TSP figured mine up to be 10.88 to one with the stock CC 5.3 heads and .030 cometic gaskets, i dont know if haveing 4cc valve releifs affect it or not.
Yes it will.
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Old Feb 18, 2008 | 12:03 PM
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Originally Posted by 405HP_Z06
Hey, thanks for that. I think you've helped me out before. From what you figured the SCR is good but the DCR is a little high for pump gas, what do you think? Can you figure it with the DCR around 8.7 or 8.6? What kind of SCR would I have with that?
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Old Feb 18, 2008 | 04:18 PM
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Originally Posted by Indiana Hawk
Hey, thanks for that. I think you've helped me out before. From what you figured the SCR is good but the DCR is a little high for pump gas, what do you think? Can you figure it with the DCR around 8.7 or 8.6? What kind of SCR would I have with that?
Don't read too much into the DCR. You will be fine. This site preaches DCR. Its not that big of a deal. Read this: http://speedtalk.com/forum/viewtopic.php?t=7463
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Old Feb 18, 2008 | 04:38 PM
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Originally Posted by HEMIETR
Don't read too much into the DCR. You will be fine. This site preaches DCR. Its not that big of a deal. Read this: http://speedtalk.com/forum/viewtopic.php?t=7463
I agreee with HEMIETR concerning DCR. I post the approximate value because people ask for it. The cam you specify will be fine for 93 octane.
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Old Feb 18, 2008 | 05:06 PM
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Originally Posted by HEMIETR
Don't read too much into the DCR. You will be fine. This site preaches DCR. Its not that big of a deal. Read this: http://speedtalk.com/forum/viewtopic.php?t=7463
I clicked on that link and it's asking for a user name and password. You got another one?
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Old Feb 20, 2008 | 09:01 PM
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405hp can you check my compression? Sorry to hijack by the way.
408, 4.030, 4.00
64cc head
JE flat tops 5cc relief
.051 gasket
pistons .019 out of the hole.
Thanks man, where did you find that calculator. It looks a lot more detailed then
the one I am using.
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Old Feb 20, 2008 | 09:21 PM
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Originally Posted by Dave88z
405hp can you check my compression? Sorry to hijack by the way.
408, 4.030, 4.00
64cc head
JE flat tops 5cc relief
.051 gasket
pistons .019 out of the hole.
Thanks man, where did you find that calculator. It looks a lot more detailed then
the one I am using.


The calculator is from Performance Trends, Inc. Amazingly, it's called Compression Ratio Calculator.
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Old Mar 12, 2008 | 04:47 AM
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Sorry to hijack the thread but what's the max DCR to use gas pump? I've been reading and some guys are afraid on running 8:1 or 9:1 DCR and I got 11.54 SCR and 10.124 DCR, I do not know if I calculated it incorrectly but 10 looks a lot to me. Hey Aaron, could you help me out? I'm just a pain in the *** I guess jajaja, thanks again you've helped me out before

I'm using 59 cc heads
3.903 flat wiseco 2cc valve relief
4.030 bore and .030 thick head gaskets
3.622 stroke
6.100 rods
0 deck height

TREX CAM @ .050
1.- Intake
duration 243.5
lift 108.3
valve closing ATDC 50.1

2.- Exhaust
duration 249.5
lift 111.5
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Old Mar 12, 2008 | 07:55 AM
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Originally Posted by MLP00Z28
Sorry to hijack the thread but what's the max DCR to use gas pump? I've been reading and some guys are afraid on running 8:1 or 9:1 DCR and I got 11.54 SCR and 10.124 DCR, I do not know if I calculated it incorrectly but 10 looks a lot to me. Hey Aaron, could you help me out? I'm just a pain in the *** I guess jajaja, thanks again you've helped me out before

I'm using 59 cc heads
3.903 flat wiseco 2cc valve relief
4.030 bore and .030 thick head gaskets
3.622 stroke
6.100 rods
0 deck height

TREX CAM @ .050
1.- Intake
duration 243.5
lift 108.3
valve closing ATDC 50.1

2.- Exhaust
duration 249.5
lift 111.5
Based on the specs above:


From a quick search, the Trex has an IVC of 76.7 at .006. There are many debated ways of calculating DCR and no one agrees upon the method or what the number really means. It's used alot on this site, but I don't put much stock into it.

My present combo is 11.31 SCR, 8.29 DCR and I have no issues.
Last edited by 405HP_Z06; Mar 12, 2008 at 08:33 PM.
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Old Mar 12, 2008 | 10:00 AM
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Thanks bro and yes, I've got 76.7 in the cam card, it would not be so far from 75, well thanks a lot. I guess I'll have no problem if you dont.
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Old Mar 12, 2008 | 08:36 PM
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Originally Posted by MLP00Z28
Thanks bro and yes, I've got 76.7 in the cam card, it would not be so far from 75, well thanks a lot. I guess I'll have no problem if you dont.
Updated with 76.7 IVC event, lowered the DCR slightly.
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Old Mar 14, 2008 | 11:38 AM
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Originally Posted by 405HP_Z06
Updated with 76.7 IVC event, lowered the DCR slightly.
Can you run some more numbers for me?

stock ls1
64cc heads
stock GM mls gaskets
224/224 .568/.568 110+4 ICL 108

Thanks
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Old Mar 14, 2008 | 07:52 PM
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Originally Posted by Indiana Hawk
Can you run some more numbers for me?

stock ls1
64cc heads
stock GM mls gaskets
224/224 .568/.568 110+4 ICL 108
Thanks
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Old Mar 14, 2008 | 11:22 PM
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I was wrong, that cam is on a 106 ICL not a 108. Don't know if that makes a difference or not.
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Old Mar 19, 2008 | 12:02 AM
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Originally Posted by Indiana Hawk
I was wrong, that cam is on a 106 ICL not a 108. Don't know if that makes a difference or not.
The above calculation is correct for the 106 ICL. I calculated IVC based on 110 + 4 instead of looking at the 108 ICL in the first post. I made a mistake initially but it was correct in the end.

110 + 4 (106 ICL) = 64.5 IVC
110 + 2 (108 ICL) = 66.5 IVC
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