C O M P R E S S I O  N

"aberson Bresident of the FullyAssed Committe" (emaxxbl) 01/13/2019 at 16:27 • Filed to: None

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MM54 > aberson Bresident of the FullyAssed Committe 01/13/2019 at 17:40

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What’s your effective deck height? With those pistons and a 64cc head you’ll be pretty close to 11:1 (figuring zero deck) - too high for pump gas.

Spamfeller Loves Nazi Clicks > MM54 01/13/2019 at 17:45

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11:1 is not even remotely too high for pump.

Porsche 9A1 runs 12:1 on 91+.

MM54 > Spamfeller Loves Nazi Clicks 01/13/2019 at 17:57

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It’s also not a carbureted smallblock chevy. There’s a lot more to it than compression ratio, but the rule of thumb for these is 10.5 or so is premium pump.

themanwithsauce - has as many vehicles as job titles > aberson Bresident of the FullyAssed Committe 01/13/2019 at 18:02

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Silvestro-san approves

Spamfeller Loves Nazi Clicks > MM54 01/13/2019 at 18:28

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The rule of thumb is also based on improper fuel and intake setup, wrong cam grinds, and over-aggressive timing, and shadetrees. 11:1 is well within envelope when the engine is properly dialed in for it. They scorch shit because they aren’t delivering the fuel.

Past that, compression is compression. Hot Rod did a build a while back with a block running 11:1 on 86 by drowning the cylinders.

aberson Bresident of the FullyAssed Committe > MM54 01/13/2019 at 19:17

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i’m gonna run a pretty thick head gasket so i should be good

MM54 > aberson Bresident of the FullyAssed Committe 01/13/2019 at 20:32

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That should do it! Once I get the bottom end parts mocked up (after line hone and bore/hone) I need to see what sort of stick-out I’ve got in mine to see how much headgasket I’ll be needing.