Timing is all relative to head design, temp, comp ratio, fuel, atomization, bore size, dome, and rod length. To make the most power the plug should fire to enable peak cylinder pressure around 15 degrees ATDC. I am speaking here of factory iron heads. To start a BB mopar has a lousy plug location. The chamber isn't the best eithier. So it takes a fair amount of timing to get peak pressure at the desired time. The larger the bore or adding dome to the piston requires even earlier timing. There is a flip side. The closer the peak pressure is to TDC the greater the chance of detonation. Detonation doesn't have to occur very long before the onset of damage. A little high air temp, little bad batch of fuel, a little oil in the cylinder and you are in trouble. A bigger bore 400/440 with a dome might need an extra degree or two when compared to a flat top 383. So what it timing worth in ET? Depends. but I'll give you two instances where less was better. #1 Duster street car, 10.5-1 340, cam , headers. Set at the recomended 35 degrees for a iron head small block. Runs 13.15, 13.16. We reduce the timing to 33 it goes 12.88. Next pass 31 degrees, 12.64. Next shot reducing timing slowed it down, 31 was best. #2 my current 64 Belvedere. 4.5" bore, 15-1 w/flat top piston, Indy-1 heads with far better chamber design and plug location. Most run these heads are run up around 37 degrees. We normally run 34. The car has been 8.96. We slow it down to run 9.25 index. Pulling the timing to 27 degrees kills about .10. So not much. If we cant gain mph with more timing, it doesn't get any more. Hope this helps your learnig curve. Trust me back in the day I owned a car that was a piston melter. It took a few sets before I realised that it had about 4 degrees to much timing. I still own it. Hasn't hurt a piston since 1991.
Doug
