Well, not an issue anymore. After a week or so of troubleshooting the problem ended up being a worn out control module on the HEI distributor on my Chevy big block. ( don't worry I also have a 72 Cutlass with HEI) I swapped this out about 17 years ago to replace the stock points dizzy as an upgrade. Best upgrade I ever did. After replacing the coil/cap and rotor, it came down to this last component which fixed the starting problem I was having. I wanted to use AC Delco, but these are getting hard to find. I read horror stories online about other aftermarket brands, but had no alternative so a NAPA part sits in there presently. My question is, what experience have you guys with HEI had with replacing these parts as far as durability, reliability, etc.? I even had a hard time getting my hands on the heat sink compound you use during installation.( got some from a computer store) any thoughts, experiences appreciated.
Chumley

 

I've had this MSD HEI with the vacuum advance limited to 12* in my car since 2011, so far trouble free. I run a 30A relay activated off the ignition switch feeding 12v via the horn relay power post. I think most HEI problems arise from low voltage sources.

 

Carry a spare HEI module in the glove box and the tools to replace it on the road. It’ll get you out of a jam someday.

Maybe a coil too.

 

I have drove the truck a couple of times, starts right up and runs fine until I put my foot in it to accelerate, then I get some stumbling and popping, no power. Engine NEVER did this before, even with the tired cap and rotor. I have a new ProForm cap/coil and rotor, with a NAPA brand module. I 've read where you should match the coil and module. What the heck does that mean? I still suspect the module, I have ordered a AC Delco one. From what I understand, doesn't the module basically replace the job of the breaker points? This is not a high performance engine, but being a big block does get up and move. Is it possible for the advance weights to get stuck or out of position upon replacement of the cap? Checked the line for the vacuum advance and it looks good.

Chumley

 

What are your timing settings? Is it a rapid fire popping in the carb when you try to accelerate?

 

No, I would not say rapid, just like its missing badly. I admit I have not checked the timing recently. It was around 8-10BTDC when I originally installed the distributor. All the wire connections seem to be good and tight. It's one of those head-scratchers where everything else remained unchanged except the replacement parts.

 

Second the idea of keeping a spare in glove box. Pulled car out of garage one day and it stalled, would not re-start, replaced module. Not any previous issues just died, luckily it was in driveway.

 

8-10* is not enough with an HEI, should be 16/18* or higher if super tuned. You cannot use points distributor settings on an HEI, the curve is different. Also you need to pull the resistance wire, HEI's need full battery voltage.

 

Got it, I installed a new engine harness at the same time, modified for HEI. Voltage was never an issue, also the engine was running great at all throttle ranges. 16-18 seems a bit much for an otherwise stock 402. I still think its something with the new parts, thanks for the insight.