I am in the process of switching to E-85 for my motor.
(520 RB, 7.1 Rod, 10.7 deck, .005 down, Ported TF 240 heads 360 cfm)

The highest CR I am finding for these pistons is Icons, which will come in at a little over 12:1.
What company would get me to about 14:1 without having to have custom pistons? I think someone had said Diamond will do 2 changes for like $40.

Is the jump from 12-1 to 14-1 worth it?

My cam is 260/266 @50.

Wallace says I will have this for cranking pressure with 12:1 which seems reasonable-
CID is 520.16 CID
Effective CR is 10.47
Cranking Pressure is 248.60 PSI
Gauge Pressure is 233.75 PSI
Atmos. Pressure is 14.85 PSI

with 14:1 it jumps to this

CID is 520.16 CID
Effective CR is 11.99
Cranking Pressure is 292.57 PSI
Gauge Pressure is 277.72 PSI
Atmos. Pressure is 14.85 PSI

My car is mostly strip with some local drive around, 4 speed, 4:10 gears.

Is 233 lbs to high anyhow with the 12:1 , my present cam, and E85?

If i jump to 14:1, what would be a reasonable duration to go to on the cam?


Thanks in advance.