Re: HEI Module any difference in SB and BB
Distributor could have been loose and simply moved on you. Timing chain could have jumped a tooth (or more), distributor gear could have jumped a tooth (or more.)
Sounds like the module is not the problem from your description. To summarize what I read - it was running good with old module, then suddenly running bad with old module, switched module, still running bad, checked timing, timing way off.
I would pull the distributor and look for any funny business at the cam/distributor gear first.
Question. If vehicle was timed 18 degrees before TDC and ran great. then all of a sudden it ran like crap. Decided to change module and now timing mark at idle was in the 12 o clock position the only thing I can figure is the balancer slipped.
1972 Chevelle, 454, 200-4r non-lockup, 12 bolt 3.73
1981 Camaro Z28, 355, TH350, 3.73