EAtDUST

Anyone know what benefits there are from running lower compression in an EA.
What performance gains would you expect by fitting a 4.0 head to a 3.9?

Soxx

There are no benefits. Higher compression (to a point) is what you want.

Rick.

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4L I6, naturally aspirated producing 173.5rwkw.
14.410 @ 96.49mph with street radials.
What's that?..... Did I hear you say TQE power?

thehat

you want lower compression if you
go forced

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previous cars
EA Fairmont ghia
EA brock PBS031

current car

Chev Camaro Iroc-Z

EAtDUST

So what gains can you get by raising the compression?
Is it just a matter off shaving the head?

thehat

thinner head gasket will raise compression
shaving the head will do it also

__________________
previous cars
EA Fairmont ghia
EA brock PBS031

current car

Chev Camaro Iroc-Z

thehat

http://www.sdsefi.com/techmods.htm

did a bit of searchin though got this stuff in books

Increasing the compression ratio is another way to increase power. It also increases fuel mileage. Unfortunately, the pump fuel available in most areas limits the compression ratio useable on the street to under 10.5 to 1 on most engines. The difference in power is minimal going from say 9 to 10.5 to 1 and it is a lot of work to shave the head or install new pistons. Again, if you get stupid and try to run an 12 to 1 CR on 92 octane fuel, you will suffer with lots of pinging and eventual failure. Many high compression street engines must have their timing severely retarded to avoid detonation which reduces the power right back to stock levels. Don't raise the compression ratio too high!

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previous cars
EA Fairmont ghia
EA brock PBS031

current car

Chev Camaro Iroc-Z

Rollin

i have also read that due to the length of the stroke in the I6 the power increase you recieve from increasing the compression ratio above about 10:1 is offset by the power required to shove the piston up the bore against compression pressure,(due to the pressure acting against such a long 'throw' of the crank, so i personally would not go any more than 10:1 in a N/A application for a falc I6.

did that make sence?

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SiX_iN_a_RoW

yes i have read the same thing rollin, apparently there is little to be gained from a higher compression ratio in the I6, however I guess every little bit helps

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