begining to plan the build of my 454 street motor. looking for a general consensus on what is the ideal / optimum compresion ratio to use on an iron head 454 on pump gas - by which i mean 91 octane as that is the max available here.
as always - thanks in advance.

Under 8:1 dynamic compression most likely, 7.8, 7.9 to be safe is probably pretty close. Don't get too aggressive with it in case you catch that occasional bad batch of gas, as I seem to do. graemlins/clonk.gif

Check Pat's site out for some background....

http://cochise.uia.net/pkelley2/

need more information what kind rpms you want to turn,gearing,stall,carb size. need a basic idea of what you want to do.

you can build a 11+ to 1 street engine that runs on 91 octane...but its going to have a big cam run 3500+ rpms .

or you can run a safe 9.5 to 1 ratio which will allow you to run a number of small street cams say under 235 duration at .050

i think you might be asking how much can i get away with on 91. we just need more info.

im running a true 10.5 to 1 comp. ratio with a 233/239 @ .050 cam in my bbc and its very happy with 87 octane fuel. but alot of work went into it to allow this. (timing curve) even with 2.73 gears and 3900 lbs.

Ahh yes, I thought that the answer might not be that straight forward;
looking for lots of low end torque for the street, will not spin the motor any more than you guys say is safe, current gearing 2.73 planning 3.55, stock stall of 1000 over, 750-800cfm carb.
I have the block but I am just in the planning stages right now, I am limited to 91 octane. I see many combos in the magazines and on this site at say 11:1 and higher, also many at 10:1 but less and less at 9.5:1 and less. If anything I am obviously looking to error on the conservative side.

My engine loves 91, never a ping. Plenty of Tq too!!!!

Aluminum heads or iron? On my aluminum head 496 the compression was 10.72:1. Low end torque - how about 495 tq at 2,500 rpm, peaked 602 tq at 4,800 rpm. If iron heads then I would shoot for something between 9.5 to 10:1.

Thomas

I have one thats 10.5- 1 and one thats 11-1 both will run on pump premium,, but like it alot better with 3 or 4 gallons of Cam II