[Ramairnacho]

Originally Posted by steve25

In a nut shell that effect / action is due to the expansion ratio.
We are all too use to looking at the compression ratio and the pistons travel up the bore.
The thermo dynamics involved in the expansion ratio looks at residual heat left over once the crank has rotated passed the point where it can still use that heat to power it.

A high compression motor burns its inhaled air and fuel much faster then a low compression one and Is why less total advance is needed as compared to a low compression motor.

The post last week of the W72 400 motor build and the 42 degrees of timing that was employed is a clear cut example of this!

Thanks for the good info. I need cooling , timing , dish,forged rods,heads build right, stainless values,new guides, roller cam, brass plugs,distributor recurved, rear end should be 308 or 331 ,and need to figure out Trans and tires size too. I'm slowly getting there. I n not sure why everyone knocks the 273 252 or 242 gears they where found in Trans am and formulas in the late 70 s and with those gears I think.gas milage is better or am I wrong? But at end of day I might slap some 331 posi and scream down the freeway at normal speed limit getting 10 miles to the gal. Not!