Engine Compresion Ratio?

marks89 · Oct 8, 2012

whats the max compresion i can go one my 347 and run on premium unleaded? any imput would be great appreciated.

twistedwankel · Oct 8, 2012

I ran 10:1 on pump 93 octane unleaded with never an issue with a carbed very basic engine using no computer at all.

BUT your spark advance and computer controls will have alot to do with what you can do like a simple "knock sensor"? Modern computers allow up to 12:1+ with the right sensors. You building a diesel?

Gearbanger 101 · Oct 8, 2012

Depends on the octane. My buddy was getting away with 10.5:1 on 91-octane a while back...but he had to back the timing down quite a bit to do so.

88LX5.Oh · Oct 8, 2012

My dad's drag car has 10:1 pistons with 60 cc combustion chamber heads and we've run it on 93 octane

Jace78 · Oct 9, 2012

It's tricky because you can time it back, then advance at the track with additives/race gas...

srtthis · Oct 9, 2012

i know a few guys running 11.5:1 on pump gas

Rick 91GT · Oct 9, 2012

11:1 is about the max I try to put in a street car with 93 octane....the cam is also critical as you can play with the cylinder pressure to make it work.

A typical 4cc flat top on a 54cc chamber head barely gets u 11:1

srtthis · Oct 9, 2012

rick you tried doing anything really high since you guys have E85 right in town?

89stang1 · Oct 9, 2012

my 333 stroker is 10.7:1, Probe 4cc flat top pistons, runs on premium no problems RNH Performance built

marks89 · Oct 9, 2012

im actually gonna have to drop compression on it. its in my race car right now am gonna change heads and cam so i can run fuel injection and nitrous. it has 7cc domes. droping compression with thicker head gasket. will be aluminium heads. want to push as much compression as possible. thanks for the imput. mark

Rick 91GT · Oct 9, 2012

N20 loves compression.... what's the combo and specs? Thicker headgaskets can be an issue with increased quench.

D- they pulled all the e85....

srtthis · Oct 9, 2012

Rick 91GT said:
N20 loves compression.... what's the combo and specs? Thicker headgaskets can be an issue with increased quench.

D- they pulled all the e85....

Well that just blows

marks89 · Oct 10, 2012

i will be changing cams, ill call comp for custom grind. heads are set of ported svos and a trickflow track heat thats supposed to be ported. my 347 is a dartblock with eagle rotating assembly, i think throttle body and mafs is 75 also. 42 over injectors and 140gph fuel pump. bought street car and love it so much want to put my 347 in it and maybe sell race car or build bigger motor for race car.

marks89 · Oct 10, 2012

rick 91gt do you think keeping compression around 10.5 solve posible quench issue.

Rick 91GT · Oct 31, 2012

How many cc are the head chambers? Your staying with a 7cc dome?

marks89 · Oct 31, 2012

not sure yet will cc them then determine thickness of head gasket needed.

reldla1996 · Oct 31, 2012

I'm running 10.6 on my 369 with AFR heads and 92/93 pump gas with no issues.

Engine Compresion Ratio?

marks89

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Gearbanger 101

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srtthis

the guy doing it does every local racers rear end

Rick 91GT

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srtthis

the guy doing it does every local racers rear end

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marks89

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Rick 91GT

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srtthis

the guy doing it does every local racers rear end

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