Compression Ration for a GEN3R Build

[jon_0_3]

Hello all,

I am planning the rebuild of my Mach 1 and need some help figuring out what compression ratio and why. I have not pulled the motor yet so I do not know if it will need to be cleaned up and bored over or not. The plan right now is stock stroke and e85 all the time. Im in Wisconsin and the gas station a mile away from me has e85 so why not. Car will be a fun weekend car not a daily driver stuck in traffic. I am planning on running a GEN3R and if i keep a stock pulley set up thats 18lbs with room to grow. What is the current thought on compression? Reading the older posts I saw a lot of people say stay around 9.5 or 10:1 but most of the posts are early 201X. I have talked to a few builders around me and they are still split. Some saying dont go any higher then 9:1 and others saying 10+ most of these are smaller shops or younger shops plus none of them Tune so still trying to find where to go. What are you thoughts and thanks for the help.

 

[01yellercobra]

If it's an E85 all the time car I wouldn't go under 10:1. A guy on one of the S197 forums ran 12:1 with a big bore stroker and a GT500 blower. I think the M122 since that's what he could find cheap.

 

[biminiLX]

For E85 full time 11:1 don’t fear the compression on E!
-J

 

[11Sec_Lx]

I agree with these guys. If you'll be on E85, bring on the compression. It will be more responsive out of boost and in boost. I'm running a 5.2 block x 5.0 stroke engine with 11.3:1. It's 99% street, made 1101 rwhp with a Gen 3R and I drive it around like that, even on 20's. It's a riot.

Sent from my SM-G988U using Tapatalk

 

[4sdvenom]

Like others have said if E all the time go 10.5 - 11:1 and bring on the boost. I’m building mine with 10.5 but only because I want the option to run 93 if I have to otherwise it would be 11:1. 2003 Cobra, 3.0 Gen5 Whipple with MS3 Pro and real time automatic flex fuel tuning adjustments.

Ken