Hi everyone. I have a 72 Malibu and i converted it over to a HEI system with a MSD-6A ignition box about 4 years ago. The car ran fine, never had a problem with the ignition and starting ever, aside from a bad battery once. I parked the car about a year and half ago so i could do some body work to it. I started it every now and then to get it out of the way and never had a problem. One time I tried to start it and the battery was completely dead, it wouldn't keep a charge from the charger either. So i would jump it, move it, jump it again, move it. I did this several times. Then i was gonna drive it again so I put a new battery in and tried to start it. It wouldn't start. Now the last time i jumped it, it started right up. So i narrowed it down to the MSD and replaced it with a regular ignition module for the time being. Car worked fine or 2 days and blew the module again. Now my question is: can a different size battery mess up a module like that? I did put a different battery in it cause i didn't have the one i had in it originaly available. The original battery was a was Douglas 24-675 battery. I replaced it with a Douglas 58-775. Would that cause the problem? Each time the module went bad was when i went some where, shut off the car, did what i had to do, came out and it would not start, just cranked over and over. Seems like when i shut off the key, it would send a voltage spike maybe to blow it out? I dunno. Any help would be great, thank you. Oh yeah, the charging system is a one wire job that goes directly to the battery from the alternator. That works fine. One time the regulator went bad and it was charging 16.5- 17 volts. I fixed that though. The problems may have started about 3 or 4 months after that. Everything was workin fine when i parked it so that's my problem, thanks. 355 motor, thm 350 p/s p/b