The Cooper crankshaft is cast.

The Cooper S crankshaft is forged.

Are there specification differences also?

 

I believe all of the other factors (journal sizes, flywheel bolt pattern, harmonic balancer shaft sizes) are the same, but since the S engine (forged crank) has forged rods instead of the powdered metal standard rods, there might be a difference in balancing. A forged crank is heavier than an equal-sized cast crank, so the bobweights (counterbalance) are heavier than cast bobweights of the same size.

 

Forged Crank is also stronger than merely a cast item. So if ya wanna build a he-man motor, start with the forged pieces.

 

what do you mean by a difference in balancing? shouldn't a crank be evenly balanced in order to turn smoothly?


I know a forged crank is stronger, that is why I want one. But I do need to know if there are any characteristics that would help or hinder the performance of a Cooper engine.

 

typicaly, a crank, stripped of all rods, is balanced by bolting weights on each rod journal equal to a percentage of the conrod weight. it is then spun and the counterweights ground to balance the shaft radially and axially. Sometimes the harmonic balancer and flywheel are included, sometimes they are independently neutrally balanced (usually better)