Uh Oh, Too Much Compression?
10-30-2007, 07:30 PM
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Uh Oh, Too Much Compression? HELP!!!!
So I am about set to order the new cam/trans./gears/flycutting stuff and then I come across this thread
O NO.... https://ls1tech.com/forums/generation-iii-internal-engine/806151-milling-205-afr-s.html
So I am reading along I see post #16 talking 59cc AFR 205's (which I have) and someone using a cometic .040 gasket (which I was going to run). He says that the compression on that would be 11.83-SCR which as I now understand is in the zone of requiring a much higher octane gas? Also, he wrote that 59cc is .042 milling and I have heard from most other places that it is .030. Someone with knowledge could you fill me in... I'm really hoping I catch a break on this one.......
-Rob
So I am about set to order the new cam/trans./gears/flycutting stuff and then I come across this thread
O NO.... https://ls1tech.com/forums/generation-iii-internal-engine/806151-milling-205-afr-s.html So I am reading along I see post #16 talking 59cc AFR 205's (which I have) and someone using a cometic .040 gasket (which I was going to run). He says that the compression on that would be 11.83-SCR which as I now understand is in the zone of requiring a much higher octane gas? Also, he wrote that 59cc is .042 milling and I have heard from most other places that it is .030. Someone with knowledge could you fill me in... I'm really hoping I catch a break on this one.......
-Rob
10-30-2007, 07:42 PM
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Maybe .042 milling if you are refrence to 241's and .030 to 243's?
241= 67cc; 243= 64cc
To my specs Im running 11.9:1 on 93, so far no knock retard but I forget how much timing I have.
241= 67cc; 243= 64cc
To my specs Im running 11.9:1 on 93, so far no knock retard but I forget how much timing I have.
10-30-2007, 07:47 PM
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In Cali. it's really hard to find 93 and if we do you have to give the gas station an arm and a leg for it...Basically, I will only be running 91, unless I find myself somewhere close to a race track
10-30-2007, 07:54 PM
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On AFR heads, a flat cut @ .006" = 1cc. I have .036" cut from mine for a 59cc combustion chamber. I would have no problem running .045" Cometics with a nice quench and 11.5 to 1 compression ratio.
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10-30-2007, 09:11 PM
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Im gona be right at 8.86 and im in texas with decent gas. Im using every anti detonation trick in the book. I would try to get yours to around 8.5-8.6 to be on the safe side.
10-30-2007, 09:13 PM
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DCR is what you need to look at, not just SCR. Obviously the cam is a big part of the equation. 8.87 is slightly more than I shoot for with 93 octane, but if your not getting any KR then all is good. I think 8.6 - 8.7 is ideal. The higher you can get away with the more torque you will have, all things being equal.
10-30-2007, 09:32 PM
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So the thing is all this talk is with the cometic gasket right? I think I am going to use the GM MLS gasket, rather than the cometic, I would much rather lose a few ponies and have a motor that wont blow
10-30-2007, 10:08 PM
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You can get cometics in different thicknesses. If you want to lower your DCR a little, recalculate it with .045 and .050 gaskets to see what you need to put it where you want to be.
