compression question

[02400exer]

can i run a 12:1 piston o 93 pump gas in a 400ex

[400eXr1d3rZ]

No.

[ohsobad_chevy]

11:1 should call for a mixture of pump and race.......anything below 11, you will be fine with pump gas (93) 12 and above should be race gas only.

[02400exer]

okay thanks i didnt think you could in a 400ex i thought 11:1 to one was the biggest compression you could run but i know the new 450r come stock with 12:1 compression is the reason i asked thanks for the help

[Black R/T]

ive got 13:1 in my 400

[400exrider707]

You can definitley run pump on 11:1 in a 400ex. I ran 87 a few times...

The 400ex pistons aren't even correct advertised compression ratios. I would probably still run race/pump mix on 12:1 if not full race, but thats just me. It is an air cooled motor dont forget. Also with the right cam you can run lower octane as well.

[400eXr1d3rZ]

Originally posted by 400exrider707
You can definitley run pump on 11:1 in a 400ex. I ran 87 a few times...

The 400ex pistons aren't even correct advertised compression ratios. I would probably still run race/pump mix on 12:1 if not full race, but thats just me. It is an air cooled motor dont forget. Also with the right cam you can run lower octane as well.

What cam might that be?

[400exrider707]

Originally posted by 400eXr1d3rZ
What cam might that be?

Well any cam will help in this matter, just some are different than others. A long duration cam with big overlap will help to cool the motor a little bit.