Run the timing up at idle slowly until it stops picking up rpm. That’ll tell you where it wants idle timing. With 255/260 @ 050 and depending on your compression, fuel, and overlap I’m gonna say it might want more than 18. We had to make our own bushings to get more initial on the race truck as the black MSD wasn’t enough. MSD has good graphs for their springs. I usually start with one light spring and one medium spring and that brings it in pretty quick.
