Uh Oh, Too Much Compression?
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
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.
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
TECH Enthusiast
Joined: Dec 2003
Posts: 535
Likes: 0
From: Warner Robins, GA
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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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.
TECH Fanatic
Joined: Feb 2004
Posts: 1,259
Likes: 0
From: Lexington, KY
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.
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
Wrong!! Mamo spec' ed my stuff 59cc 11.3:1 .040 cometic, no issue what so ever on 91 octane. My car runs great we have the worst gas in the country in Oregon.
Theres nothing wrong with your setup. Call Tony Mamo next week when SEMA is over and ask him. He knows AFR's better than anyone else, dont be panic'ed. I run the same head at 59cc. Different cam but if thats all you need to do then your fine
