Shaft may be skipping out, falls on it's face when rpm's go up,.......................B-RB dizzys spin backwards.....the vac can would come in from the wrong side and the
mech adv plate would turn the wrong way...........I actually thought of doing this(with the correct shaft & mech adv unit) in the reverse, a SB housing on My 383 to use
the vac adv/plate system to retard the timing when i hit the NOS. Sounds very likely by symptom anyway.......................
