As some may have seen I tend to post up seeking advice and wisdom from the car guys among us as I’ve starting driving and working on my 73 Nova more and more. I’m not a knowledgeable car guy. I know only a little and have done less. But I want to try and tackle all that I possibly can myself as opportunities present themselves. Just wrapped up changing rear shocks, rear shoes, rear shackles, and front brakes when I discovered the next project.

The car, since I’ve started driving it again almost a year ago, and even before I stopped driving it maybe 8 years ago, stumbled a bit when you get on the throttle. In a past thread it was suggested a vac leak might be the problem. So I was spraying the carb cleaner around when I noticed the plug wire at the 12:00 position on top of the distributor (HEI type) looked odd... it didn’t seem to be sitting as low as the other wires. So I poked it. It was loose. I tried to push it down but it just won’t snap in like the other 7. Looking at the stud it’s got obvious corrosion. The contact in the wire is rusty. Maybe I’ve found my problem?

So I started the car back up and now, looking with purpose, I can see arcing between the stud and the firewall, which is right there. Very tight clearance.

So it seems obvious I should replace the cap and wire set. What I’m wondering is if I should consider buying a rebuild kit like this:

Pro Form 141-796 GM HEI Distributor Tune Up Kit (Black Cap), 1 Pack https://www.amazon.com/dp/B071...cp_api_8G2zBb45CB614

And then I wonder about the plugs themselves...

The plugs have been changed since I’ve owned it, back before I originally stopped driving it. They might be 10 years old.

I have had the cap and wires replaced once, but never the other stuff in the kit.

So, should I do the cap and wires only or the whole shebang? Plugs too?

This message has been edited. Last edited by: thumperfbc,

Did you install an HEI distributor or was it on the car when you got it?

For a 73, it should have points and a separate coil.

Just get a stock cap, rotor and wires from Autozone, O"reillys or pep boys. High performance stuff like accell or stuff like that won't matter on a street car.

And toss in some new plugs. Get AC delco oem, again, no accell or ultra spark or that crap. For 20 bucks, factory plugs are fine.

quote:

Originally posted by barry1967:
Did you install an HEI distributor or was it on the car when you got it?

For a 73, it should have points and a separate coil.

Just get a stock cap, rotor and wires from Autozone, O"reillys or pep boys. High performance stuff like accell or stuff like that won't matter on a street car.

And toss in some new plugs. Get AC delco oem, again, no accell or ultra spark or that crap. For 20 bucks, factory plugs are fine.

It’s not the original motor. The previous owner put in a GMPP ZZ4

Check with your local NAPA store and see if they still have a brass contact distributor cap available. I personally prefer those over the aluminum contact ones. Also replace the distributor rotor at the same time. For the wires, Delco preferred by me.. Especially that unless something has changed they are limited lifetime warranty covered. For fitment, use 75 and later Nova or Camaro. If I was still "in the business" (GM parts department) I would get you the part number.

Watch the side lock tabs on the wire harness connectors, they are prone to breaking. Pretty common. They will plug in and can be used without the clip ends, the clips are insurance that the connectors will stay together.

One thing with that kit you linked on Amazon. I did not see any insulating grease with the items pictured. If you do not use that insulating grease between the module and the distributor housing I can guarantee that any module will soon fail. It is a heat insulating grease, seen a bunch of those burn out when it was not used.

quote:

Originally posted by shovelhead:
Check with your local NAPA store and see if they still have a brass contact distributor cap available. I personally prefer those over the aluminum contact ones. Also replace the distributor rotor at the same time. For the wires, Delco preferred by me.. Especially that unless something has changed they are limited lifetime warranty covered. For fitment, use 75 and later Nova or Camaro. If I was still "in the business" (GM parts department) I would get you the part number.

Watch the side lock tabs on the wire harness connectors, they are prone to breaking. Pretty common. They will plug in and can be used without the clip ends, the clips are insurance that the connectors will stay together.

One thing with that kit you linked on Amazon. I did not see any insulating grease with the items pictured. If you do not use that insulating grease between the module and the distributor housing I can guarantee that any module will soon fail. It is a heat insulating grease, seen a bunch of those burn out when it was not used.

Rock Auto has Delco brass caps for $15...

What about this kit? Just add plugs? Is there no needs to spend money on a new module and coil?
https://www.rockauto.com/en/pa...8836,tune-up+kit,684

Modules and coils rarely went bad from my experience.

Early Delco HEI modules (very late 1974-75 OEM) that were white plastic had a high failure rate. I don't remember all the particulars, heat related failures IIRC. They were replaced by the black plastic ones. If a module fails, the "usual" failure would be to lose spark and shut down. Would restart after about a half hour to an hour cool down time. Would then run/repeat the cycle. One major cause would be improper installation, no insulating grease between the metal heat sink at the bottom and the distributor housing.

Delco coil failures, very rarely. Those produced up to 45-50 thousand volts IIRC. Again OEM was good quality, saw more damaged by improper installation than anything else. Best one for abuse I ever saw had the center of the distributor cap melted out, the carbon button between the coil and the rotor was completely shredded/burned up.This coil was jumping spark from the center where the button would be, through the dime sized hole in the distributor cap and down to the distributor rotor. The car ran, poorly, but still drove into the shop with the complaint "running rough".

I built several distributors up for Buicks and Pontiacs using "recycled" parts over the years. Biggest failure part in HEI distributors from my experience, cap and rotor due to wear and tear. The most maddening failure was the pickup coil, the one under the baseplate with the small rectangular two wire connector, a white and green wire IIRC about 20-22 gauge. That failure manifests with a miss/running rough/shutdown condition off ilde but a perfect idle condition. A quick and dirty way to analyze this is to remove the vacuum advance hose from the distributor, rev it up, now runs normal. Those small wires can break at the coil due to the advance plate moving when the advance kicks in. The correct test from the service manual would be to disconnect the two wire connector at the distributor module, connect a ohmmeter and move the wires around. Any open circuit detected, toss and replace.

This article might be some help.http://www.crankshaftcoalition.com/wiki/Hot_rodding_the_HEI_distributor

My opinion, don't change the module and coil unless there is a failure in those components.

Ok, so change the cap, rotor, and wires. Is that all pretty straight forward? Sounds doable.

As shovelhead stated a little dielectric grease inside each boot on the distributor cap and plugs will help prevent arcing to ground and weak or no spark condition to each plug.

You only need a thin layer.

It also helps prevent boots from sticking.

For the firewall, you can try something like this.
Just degrease well (Dawn dish soap or Simple green) and stick it on the firewall. It should look OK.

https://www.amazon.com/LASCO-0...0_QL70_&dpSrc=detail

quote:

Originally posted by sigmonkey:
As shovelhead stated a little dielectric grease inside each boot on the distributor cap and plugs will help prevent arcing to ground and weak or no spark condition to each plug.

You only need a thin layer.

It also helps prevent boots from sticking.

For the firewall, you can try something like this.
Just degrease well (Dawn dish soap or Simple green) and stick it on the firewall. It should look OK.

https://www.amazon.com/LASCO-0...0_QL70_&dpSrc=detail

I have serious doubts that I could fit that between the boot and the firewall. I think the lack of clearance is likely the underlying cause to this issue. A little creative ball peen hammer work might be done when the cap comes off.

You are correct. If it is that tight, it will always break through, and the side load against the cap is not doing you any good and may lift the cap, or push it off center and that will screw with the rotor contact to cap studs air gap.

Some hammer love is in the future.

Some loud Rock and Roll will help mask the noise and set the mood.

I’ll try and post pictures for advice.

Cap and wire replacing advice. Disconnect the connectors to the cap. Remove the distributor cap with the wires attached, replace the rotor and install the new cap. Then replace the wires one by one from the old cap to the new.

It does not really matter whether you replace the wires before or after you replace the cap, just don't pull them all at once. Easier one by one.

If you do pull them all at once, remember that the firing order is 1-8-4-3-6-5-7-2 in a clockwise direction. Wire accordingly.

I'd offer to come and help, but I think you would be done by the time I traveled 2500 miles one way.....

Don't make two common mistakes when replacing a HEI distributor cap. One is the ground terminal, between the two coil wires, getting left out. This will make the coil run in reverse polarity and kill it in 50-100 miles. The rubber washer (insulator between the coil and the cap) goes OVER the carbon button/spring. If you reverse them and put the button on top of the washer, the button won't touch the rotor.

Ok, so on a whim I re-routed the wire in question to approach the distributor from the passenger side instead of the driver side. I was easily able to get it to snap into place. I think Hammer Time has been avoided.

The problem is the interior of the wire contact and the stud itself are still corroded. I was able to hit the top of the stud with a wire wheel on my drill and I scraped the inside of the wire contact with a small flathead screwdriver.... we’ll see.

Trying to embed some pics from a new service....

Any thoughts on the plug? Does it look like something that needs changing?

I would change them.


AC Delco MR43LTS

You can order online or get have O’Reilly's get them for you.

Without knowing how the engine has been running, trying to "read" those plugs is going to give you unreliable results.

There is an art/science to tuning by reading plugs.

While that one has a nice tan center electrode, the ground electrode looks a bit worn, but it could be the picture.

And the base ring looks like it could be too cold a plug.


But you can get that same "reading" by an engine that runs rich, proper heat range plug, that sat idling while lean, so the center is tan, and the base ring is sooty.

So, similar appearance, but for very different reasons.

Putting in new plugs and having the ignition functioning properly, you will have a better baseline to start with.

Ok. I actually ordered the Delcos you suggested (I checked the spec sheet to see what was oem) when I ordered the cap and wires. It’ll all be here Friday. I wasn’t sure they would need changing but they were pretty inexpensive on Rock Auto so I figured at worst I could shelve them until needed.

When I pulled that plug I wanted to pull number 6 as that is the cylinder that may or may not be firing due to the wire/cap issue. But I couldn’t even get my socket over it. In fact, plugs 1, 2, 5, and 6 are all blocked by the headers. What’s the trick there?

Get pics if you can.

I have used flexible extensions (but they tend to "unwind" if too much torque is required.

A swivel or two, and there used to be a "spark plug tool, that was about a foot long with a T handle and the socket on a flex at the other end.

Sometimes a "plug socket" can be used with a box end wrench to break them loose, as it has a hex end on the "top" of the socket.

And if you can break them free (Kroil might be your friend) you can slip a piece of rubber hose over the end of the plug and turn it out as it will be flexible.

Last would be dropping the headers but you risk breaking bolts/studs.

I agree with SigMonkey in that you need to address the cap to firewall clearance.
It is way to tight and what isn't being addressed in a still picture is the motor movement when your driving, starting and stopping.
Along with gaining clearance new body, motor & transmission mounts may be needed.

If it were mine I'd look it all over and might even look at putting a whole different distributor set-up in. That newer style distributor was huge compared to the stock distributor.

^^^

Yep.

Jegs has a small head distributor that will work.

Jegs Distributor