Milling Heads

[Brock]

i am in the process of building GT-40 heads. i wanted to raise the compression a bit while i had the heads off. but with the 5.0 you already have a 9.5:1 compression ratio. if i milled the heads to get a 10 or 10.5 compression could i still run pump gas? any recomendations?

[eghonda88]

as long as you don't go over 12.5 you can run premium (93). Im pretty sure that goes for all motors.

[all-mota]

as long as you don't go over 12.5 you can run premium (93). Im pretty sure that goes for all motors.


not exactly.

most v8 had designs aren't designed to be able to run that much compression on pump gas like hondas are

[Brock]

haha yea i 12.5 on a V8 = 103 and + octaine

[eghonda88]

I know a dude who runs 12.0:1 in a hemi but its E85... Never built a V8 though. I think 10.5:1 should be fine. with high octane My buddy had a chevy with 10.5:1 it just shook like a B

[Brock]

yea they will run on lower octaine but they will run like ****. thanks for the imput, yea with a 10.5:1 you should run at least 98 octaine

[HatchHero]

Good thread

[Dietcoke]

Fuel injected you wont have a problem on a v8. It's all in the tune really, I ran 11.7:1 in my street LT1 camaro for a long time. Good to go on pump gas.

[mitch lab]

should be fine

[dynoman14]

Brock,
Don't waste the time or money on 1/2-1pt on Compression as it is only about 4% increase for each point below 12 on a normal V-8. You would be better off getting a 5-7 angle Serdi valve job, de-shrouding your combustion chamber around your intake valve and bowl blending the heads to increase the low-lift airflow. This work should easily net you 50-100 RWHP depending on the quality of the work.

With todays crappy fuel, 50 year old head designs, and most stock ignition systems street cars should stay in the 9.0 - 10.5 compression range unless serious attention is paid to the intake and exhaust systems and the fuel injection mapping and ignition system.

Honda's get by because they have very advanced engine management systems and the fuel is very close to direct injected, and the head designs are very good. Only thing I have seen that is close is the Chevy ecotec. We will be starting a development program on the engine next month and should be ready for street / track testing mid-Summer.

Good Luck,
DM14