Bad GM modules in older HEI 2x 6 cyl

[534BC]

The engines are old v-12 gasoline engines, using a pair of older v-6 HEI distributors with about 3-4 inches between them.

Both distibutors stand up and spins clockwise like they did in the original v-6. These are the large cap, coil in cap HEI from the 80's.
One runs the left bank and one runs the right bank cylinders.

The modules only last 1-6 months and then will "be affected" and not run anymore. The module tests good and will run in another stock gm vehicle for years.

There's about 4 of these dual set-ups and all 8 of them eat modules , some longer than others.

More info:

regular spark plugs, mallory pro-sidewinder wires, and a nice clean set-up. They are in heavy duty trucks that run nearly every day. I'm real familiar with the engines for many years have tried various ignition systems in them. This new double HEI is a new set-up to me. I r&r'd two modules in the same distributor for them yesterday.

Some ideas that don't help:

tin foil,lead,insulation in between the two distributors
different brands of modules,
remote coils,
remote modules
nice airflow cooling over the components

some ideas that may be the trouble:

2 set-ups on a common engine ground,ect.
2 set-ups RF energy
Use 1 reverse direction )polarity) coil
Use 2 reverse direction coils (pontiacs I think)

If anyone has some ideas that may cause the modules to go bad I will try them out and se if it fixes it and is very much appreciated.

[maxwedge]

Proper grease between the dist plate and module, correct? Also rotor to cap misalignment can cause voltage spikes in the module circuitry. Index the rotor and cap.

[534BC]

Yep on both accounts. They've been using mostly the grease or occasionally the white harder compound. I think the white compound is best.

I saw a slight black mark right in the middle of the cap post signifying the rotor relationship is spot on. I'm going to double check it.

Thanks.

[534BC]

You think the white heatsink compound may be better than the diaelectric grease supplied with echlin modules?

You meant rotor to cap alignment referring to having the rotor in the center of the post at the time of spark right?

[maxwedge]

Correct.

[534BC]

Thanks, I may heat things up with a heat gun or hair dryer soon and see if that makes them go bad. Everyone that "goes bad" tests out good from the manufacturer.

[534BC]

Can I post pics? I see no atttachment method.

Thanks, VVVV shorod VVVV here's some pics of the dual setup, it is in the stock location (rear of engine) with a gilmer belt driving the second distributor.

[shorod]

You have to upload the photos to a picture server (picasa, photobucket, etc.) then link to the photos.

-Rod

[534BC]

I talked again to the installer and even though neither of us KNOW for sure , but we both rather think that if the setup was in a gmc v-6 truck engine that it would be reliable. I then asked if it was allowed to run only half the engine with one "bad" module would the good half be reliable. We both agree that it would.

[534BC]

Some more info:

Truck makes real good power comparatively to other similar set-ups. Truck detonates very easily and overheats very easily. (Both symtoms when making power)

[534BC]

Originally Posted by 534BC

Some more info:

Truck makes real good power comparatively to other similar set-ups. Truck detonates very easily and overheats very easily. (Both symtoms when making power)

Fixed the overheating and detonation by replacing two blown head gaskets.

They had been leaking combustion into cooliong system for a long time causing vapor spots and detonation,overheating. Now we are just back to bad modules every once in a while.

[534BC]

Do you think a heat sink like this might help?

[UncleBob]

I once used an HEI module to run a toyota 22R motor....just bolted it to a heat sink and mounted it to the fender. Worked great. For that matter, people use them often to fire low impedance injectors and/or ign coils in home made EFI systems. All I'm saying is, these modules have been used for much more odd, extreme things than you describe. I see no reason why it wouldn't work, assuming you're not running a 6V system or reverse polarity, or some other unmentioned important tid bit of info!

Have you checked the ground at the distributors?

[534BC]

Hmm, I have mixed and matched many different components on the older stuff with good results too. I will double check ground on dist bodies. Maybe I will find a heat sink and mount the modules "remotely"

thanks uncle Bob.