[25stevem]

You just can’t make any type of blanket statement about what a given type chamber wants in terms of timing.

Many folks engine combo’s that are similar just have too many important factors that are different.

The propagation of the flame front across the chamber ( assuming no detonation) is influenced by many factors, of which two of the biggest are cylinder pressure rise as the piston gets close to TDC and the different jetting needs for a specific gravity of the fuel used, and not to leave out the chamber suface temperature difference between a iron and Aluminum head.

Also to stuff a third factor in there the wet flow characteristics of the intake runner and port are part of the picture too.

Big droplets of balled up fuel don’t light off if at all until the piston is already moving down the bore.

This. Creates a power loss, and sometimes a big one if the motor detonates as is the case many times when that balled up fuel goes off at a sonic expansion rate.

Even if there is no detonation the dyno guy will wrongly see a need lean out the jetting to get some of the power back that the motor should be making, but then since your putting less fuel into the motor your also in turn making less power then what could be made if all was well, and since your now lean the motor is on the razors edge of detonation once again.

It’s a very hard wall to be backed up into!!