11.0:1 306 vs. 9.0:1 306

[red82gt]

It would depend a lot on the airflow requirements, combustion chamber shape, camshaft, etc. If you put in a cam with a lot of overlap, the extra compression would help to restore the low end torque and would allow the motor to get into the powerband for the camshaft. I think it would be worth about 20 ft/lbs of torque at the low end but I'm not sure how much up top.

I think 11:1 would be a bit much for a street motor, even with aluminum heads. You'd have to run probably at least 93 octane gas and hope you don't run into a bad tank. If you have emissions testing, it may be difficult for an 11:1 306 to pass.
My car has just over 10:1 with iron heads and if you use less than 91 octane it knocks and pings like a pig.

I'd go with about 10.5:1 or even 10:1 and make the power with more airflow.