Overdrive vs. Cubic Inch

I am curious about overdrive vs cubic inch restrictions and the reason for this? Below 450 is only 2.04% overdrive while above 450ci is 2.15%.

Is there a benefit to smaller ci other than less rotating mass?

Shannon

 

Given that blower size is limited, the smaller the motor, the easier it is to make high boost.-less to feed.

 

Dragster 503,

The overdrive limits come from the SFI 34.1 spec.

The idea is to insure that the rods exit the engine while the blower is still way within its safe RPM zone. Most blown alcohol engines use the same blocks, and are able to use the same bore sizes regardless of displacement.

Long-stroke engines throw the rods at a lower engine RPM than short stroke engines, so by indexing the maximum blower overdrive to the engine displacement, the blower RPM at the instant the rods exit the engine is essentially the same.

Norm Drazy