[Bscman]

Hey guys...

Long time no post. My '72 was rear-ended on I-5 November 20, 2008. It's been in and out of the shop since then for repairs...it's been a LONGGGG ugly road!
...and no, I still don't have it back.

In the mean time, I threw a motor in the old pickup so I have something to drive. I have a problem, though! I've burned up three ignition modules (HEI) in the last 30 miles!!!

The first HEI distributor was a new pro-comp! JUNK!
I figured that was the problem, so after the first module burnt out I installed a NEW Accel "performance replacement" distributor along with the Accel performance coil and module...that lasted 30 mintes.

Module #3 lasted 25 miles and an hour of idling and tuning.

YES, I remembered the special grease on the module--this isn't my first rodeo!
The coil is getting a full 12 volts, even while cranking.
When the motor runs, it purrs like a kitten (GM goodwrench crate350 with 3,500miles on it).

I'm wondering if this is a grounding issue...???
I have a ground strap (1/4" wide) and a #4gauge wire grounding the motor to the frame, and several opthers from body to frame...#4 ga to the negative terminal on the battery.
Is this enough?

And ideas? Advice? Knowledge? Wisdom? Stabs in the dark? Anything?

I was broke before the accident, now I'm even more broke...and broken down!!!...and I can't afford to keep buying modules! HELP!!!

 

[74 hatchback]

Try a msd6a box and ditch the module, mine ran trouble free like that for 14 years with lots of daily driving.

 

[Ray_McAvoy]

Hi Bscman,

My first thought was a bad coil that's shorting out after it heats up. But I see that you replaced the coil along with the 2nd distributor/module.

Stock HEI distributors have a metal ground strap that hooks under one of the 4 coil mounting screws. It connects to the middle terminal of the 3-wire plug that connects the body of the distributor to the in-cap coil. Check to make sure your distributor has that ground strap. And that the black wire hooking to it is grounded inside the distributor body. Without the body of the coil grounded there could be some stray voltage that's burning out your modules.

Also, what type of alternator/charging system is in the truck? I've heard that some aftermarket/replacement HEI modules don't have very good over-voltage protection and can be damaged by voltage spikes produced by the old style mechanical external voltage regulators. Solid state electronic voltage regulators are available that'll plug right in place of the old mechanical ones.

 

[Bscman]

Yes, I've tried two different coils...both known to be good.

The metal ground strap IS in place, and all the wiring is in good condition and positively attached (again, new).

The truck has the complete "gm serpentine conversion kit" installed...which is the same as the early/mid 90's full size GM cars and trucks. I'd guess you've probably seen the kit from GM performance parts or summit/jegs.
The alternator is internally regulated.

The modules that have burnt up wereas follows: the factory pro-comp module, a neihoff replacement from schucks (cheap), and an accel performance module.

I re-wired the 12v source to the distributor from another source "just in case." I also added another ground strap from the engine to the frame.

I started and ran the truck 4 times today...I put on about 15 miles with no issues--but I'm still lacking trust in it's reliability.

Thanks so far for the responses!

 

[gfercaks33]

i was just asking bout you good to see your back health gotten any better lets see some pics of the nova

 

[Philip]

If the tach terminal goes to ground it will take out the module. Check the wiring for any frayed areas that could ground out that circuit.

 

[Plowman]

See if charging rate too high. 14.2volts at idle,and 3000r.p.m.

 

[The Big Al]

I re-wired the 12v source to the distributor from another source "just in case." I also added another ground strap from the engine to the frame.

I started and ran the truck 4 times today...I put on about 15 miles with no issues--but I'm still lacking trust in it's reliability.

Thanks so far for the responses!

I believe this to be your fix.

If your truck is pre-1975
The ignition wire (IE: power) is a resistor wire only suppling 9v, and in some cases the HEI will short this wire. The wire needs to be replaced from firewall to dist.

Al