Thread: Engine question 350

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I have a question on engine compression. I'm thinking about buying a engine from the Engine Factory. Is there a good & bad on 9.5:1 compression verses 10:1 just wandering.

It is generally accepted that the static compression ratio limit is at 9:1 using iron heads and 10:1 with aluminum heads with currently available pump gas.

As Denny alluded to, a major factor will be the piston to head clearance, or "squish" dimension. With all other things being equal between two motors, the motor with the tightest squish (short of a piston/head collision ), will be the most octane tolerant. The camshaft timing is just as important, establishing the intake closing point and therefore dictating the dynamic compression ratio of the motor.

The Chevy in my roadster has a .038 quench. About as tight as you can go. With the Vortec heads and Keith Black "D Cup" pistons I have a theoretical CR of 9.3/1. I'm running a mild Edelbrock Performer cam. Runs just fine on 87 octane gas and I can get a satifying cherp going into second.