vetteoz

Fitted the engine from my ’89 in my brother’s ’56 Belair .Runs like a charm but has taken out 5 ICM’s in 2 years
Ground up rebuild has all new wiring / grounds which eliminates the usual reported suspects in ICM failures.
Thinking the used F-Body dist at fault ( required for the HSR ) ,we fitted a new MSD 8366 dist and remote coil which has blown 2 ICM’s ;
the orginal and a NAPA replacement

More research online found a boating forum where power spikes from the starter were identified which ties up with our problem
that the fault only occurs as soon as the starter is engaged on a cold start after the car has sat for a week or more ( higher load on starter).
Strangely the ECM has not been effected or any codes generated

If the car starts on Sat it will start fine all weekend but blow the next Sat . Also was suggest long cable runs ( batt in trunk ) aggravates the problems.

Looking for a recommended power filter / fix for the Ign system other than this rather expensive item that protects the whole system

http://www.sto-p.com/pfp/online.htm

vetteoz

TTT

None of the resident electronic guru's has any comment ?

1963SS

As a many year industrial electrician/'tronics whiz kid we've had all sort of spikes. Our biggest was an electromagnet attached to an overhead crane. This could lift tons of metal at once and when the relay opened wow, what a spike. We controlled it with a metal oxide varistor (MOV) and it worked wonders. I'm certain that a relatively inexpensive MOV would stop the spikes if that is your problem.

You really need to get an oscilloscope on your system and see what the amplitude of the spike is. That way you'd know for sure. Also in the old days (I'm now retired) alternators had capacitors on them to inhibit these transient voltage spikes. I'm thinking that a cap would do the same duty on a starter.......but I'd have to get out my reference books and check on that. It's time for sleeps now but I'll look around tomorrow (today really, it 4:19 in the darn morning.) Happy sleeps and I'll post again when I wake up and have had enough caffeine to jump start my ancient ***.

Churchkey

Still using the stock dash ign switch? If so & if IIRC the wiring needs to be changed on the back of the switch for HEI. The info on the switch change is @ trifive.com

In the meantime suggest bypassing the ign switch start feature. Use a starter button, pull power from battery terminal on fuse block to button then to solenoid. Minimum
14 GA wire. Caution: starter button will have power to it at all times.

If using a column w/ key switch follow factory wiring for the particular car the column came from provided it is a GM column 1975 & later.

1cooldaddyo

I had a Shelby Daytona back in 1988 that kept taking out radios.
I put an o-scope on it and saw that there was 90+ volt spikes right at startup.
It appeared to be reverse emf from all the solenoids opening at once (and not a clamping diode to be found anywhere).
I put an MOV (metal oxide varistor) in from the radio's 12v supply to ground and never had anymore trouble.
I believe it was a 24 volt MOV. It was one we used for spike suppression on telcomm lines.

vetteoz

Thx for the responses.
Have been out of action for a while so no internet

cudamax

Try doubling the size of ur pos wire from the battery to the starter and dont run a high torque starter and a thicker wire from the motor to the frame. Just like when ur using an extension cord on a high torque electric saw when u want to run a longer 25ft one u have to use a real thick extension core so u dont burn the brushes out when the unit starts up because of increased resistance created by the thinner longer cord. Did u hook up a fuseable link in inline on the pos side going to the starter right. I seen starters when they go bad pull 50 amps or more on a charger when the Armature goes bad and throws all the dc power to ground so a good rebuilt one is cheep, if urs is on the way out without a fuseable link in play but all this really dont matter if u have the right protection right before all ur stuff with the right fuseable link because you'll just be blowing the links