Hi all,
I'm replacing the HEI distributer on my 69' "S" 350. Original one has a ton of slop in the shaft and looks pretty worn. I do have an MSD 6 as well so the module in the distributer is deleted. I am cleaning up the wiring since the connectors are poorly installed. Question is can I leave the capacitor in the new one or does that have to go?
Thanks in advance!

 

To me unless you are running a hard charging engine the benifits to the MSD are not worth a possible failure point. I run 11.60's with my 350 and still run a bread and butter HEI works on the street and does what it needs at the track. Just fwiw.

 

Thanks all, I installed with capacitor no issues so all good.

 

it’s pretty easy to make a jumper harness to plug a standard HEI module to bypass the MSD box. All you need is to buy the replacement 2 pin connector/terminal from MSD, and some 14 gauge wire and 1/4 spade female terminals. Bolt the ignition module to a chunk of aluminum to dissipate heat.

Assuming you have a hood ignition module, solder wires from the pickup coil connector to the replacement MSD connector. Solder wires on the other terminals to matching 1/4 quick disconnects to plug into the original 12 volt pink wire, the tach terminal on the HEI cap, and finally a grind wire from ignition module.

In the rare case of MSD box failure ( I have had mine for 25plus years) you could plug in the homemade backup module in less time than it took to explain it.

I made a jumper harness/HEI backup to run MSD distributor/6AL box equipped engine on my run stand without the MSD box that was still in the car. You could do the same, toss it in the trunk and forget about it until it’s needed.

If anyone is interested, I’ll take some pics and show what I did.

 

Thanks for the info!

 

My MSD has been stable for at least 35 years, never had a failure (although miles are limited).

 

I don't feel the need for more spark and I spin my 350 olds to 7k regularly at the track. The MSD has it's place I think for the average guy it's more or less a waste because the average use will never see the added benefits.

 

With the possibilities exception of the rev limiter on the 6Al box!!

I agree, it’s pretty hard to beat a GOOD GM HEI system. The early modules did have some reliability issues the first year or so if production, it didn’t take long before DELCO figured it out. Unfortunately, the myth that ignition module failure is a common problem just won’t go away.

If your having module problems, it’s most likely ignition coil related. Granted, the stuff sold in the parts stores today isn’t the best quality. I personally would rather have a good used Delco module from the late 70s than the parts store crap today.

I put the MSD box in my car so I could use a 2step, nitrous retard, and other benefits offered with aftermarket ignition. For 95% of people with a classic street car, HEI will get the job done reliably and cheaply.

 

Matt, I am interested in having you post pics, etc.. I would think others are also. Thanks!

 

The features are the best things about the MSD. Start retard , 2 step and all that stuff totally agree for a race car that calls for it. Even on the street for high compression engines you can just have your coil on a switch so it can turn the engine over for a second or 2 then you flip it and it starts . Like a poormans start retard.

 

Next time I’m in my shed I’ll grab my backup module. It’s been below zero here with some snow, getting the shed doors open will be a challenge!!

 

I agree based on my personal experience.

I have a factory GM HEI from a 78-79 403 engine and it has been running perfectly on my car since around 1982. Still has the original ignition module, all I did was recurve it using the springs from a Moroso HEI recurve kit, and made an adjustable stop for the original 24* vacuum canister so I could set it to 10* or so.

Oh yea, my car also has a mechanical voltage regulator, been there since before the HEI was installed 40 years ago, and the ignition module hasn't failed due to "voltage spikes". The urban legend says those create voltage spikes that will kill the HEI module and you must use a solid state regulator with the HEI distributor. Not my experience at all.

 

No rush Matt. I understand the snow problem and sub zero temps, that's some of the reason I have never moved back to the north. I spent enough years in northeast Ohio; don't even like to go up there to visit unless it's sunny and 70s!

 

I don’t mind the cold, I don’t mind the snow. I despise the sub zero temps we have had.

 

Finally remembered to dig my creation out of the shed. Here are some pics.

Here is a spare ignition module screwed to a chunk of aluminum. Since the module is no longer inside the distributor, I don’t think a heat sink would be absolutely needed. But I had the aluminum, I used it.

A old HEI module harness connector.

Alligator clips for power/ground.

This is a wiring diagram for a Delco module. I downloaded years ago, it’s displayed along with other useful info on my “wall of knowledge” in the garage.

Spare MSD pickup coil connectors.

From the MSD6AL instructions.


If your 10 miles northeast of nowhere and your MSD ignition box fails, you could plug this in and be back on the road in 5 minutes.

 

I've installed many MSDs for friends and club members. I always use an MSD 8830 26 mF capacitor or a generic equivalent on the 12 V input. I've not had a failure on any of those.

The only MSDs I've seen fail didn't have a capacitor. So I suspect electrical glitches (from battery chargers, etc.) contribute to their deaths.

If you are set on keeping your MSD, use a capacitor.

 

What does the capacitor supposedly do? Other than filtering some noise, I can’t see any need for it. And if the car has a noisy electrical system, I would think fixing/replacing the alternator would be far more beneficial than a band-aid.

I personally know of 6 friends who have 6AL boxes on their cars and trucks, all of them are at least 15 years old. The only one who had problems was due to hooking up jumper cables backwards, but that’s no fault of the MSD. He didn’t know he had ignition problems until after rebuilding the alternator, replacing several fusible links, etc.

Important tech tip: if your going to use red and black battery cables, make sure you follow the common sense color coding!! This car had replacement cables that didn’t color coordinate in the usual manner.

 

MSD's capacitor filters the power going into the MSD. It's large, it filters big, damaging spikes from external sources; it's not meant to filter noise.

I'll send you a PM to explain the details, rather than hijack this thread further.

 

Thanks for the pics Matt!