1985 350 HEI dist. replacement

[hatzie]

The moolie that let the magic smoke out of whatever part should never be allowed to touch your truck again.

Supposedly the ESC distributor was only used on the LE9 305. If your truck started life with either of the 350 engines or the LF3 305 it wasn't equipped with ESC. Big Cap ESC is easy to distinguish from a regular Big Cap HEI. With the cap off you'll see two sets of wires exiting on opposite sides of a big cap ESC distributor body. Three wires out one side are attached to the cap, just like a regular big cap HEI, and an extra Weatherpack or Metripack connector (ESC harness) attached to a harness running through the firewall. The ESC engines also have a spark knock sensor screwed into a block water jacket drain plug hole just above the oil pan rail. And last but not least. The ESC ignition module under the rotor has 7 electrical terminals instead of 4.

It's not rocket science to replace the HEI control module. They're nowhere near the cost of a whole reman unit. Usually right around $15 for the AC Delco module. Don't get me started on the Chinese floor sweepings you'll end up with if you buy a brand new distributor.
The HEI module amplifies the magnetic pickup signal to drive a power transistor that switches the coil ground on and off. The distributor body is a heatsink for the transistor... this is why the new module will come with a tube of heatsink grease. Be sure to use it.
The only reason it might fry again is if the harness attaching it to the coil is loose either at the module or at the cap connection.
The original AC Delco modules and coil worked quite well up to some fairly obnoxious RPMs. Unless you intend to drive with the RPMs in the stratosphere for extended lengths of time the stock replacement AC Delco module is the best bang for your buck and the most reliable. The recovery time on the coil was the limiting factor. Modern coils are capable of 7500RPM plus with the stock module. You'll start to see mechanical problems at that speed so the coil is no longer the limiting factor.

As long as the shaft doesn't have a bunch of play side to side and the advance plate isn't flopping around like a wet noodle the distributor you have will work just fine with some inexpensive TLC.

You can replace the advance counterweights, plastic counterweight pivot bushings, and springs if they are too loose. If the distributor needs to be re-curved you'll be replacing them with a new weight and spring set anyway because that's part of how you re-curve the advance. The Vacuum can should be tested to make sure she doesn't leak... If you are keeping it... or just install the new can for your new advance curve.

Hot-Rod Car-Craft HEI Ignition Module Testing
Read this article as well...
Crankshaft Coalition Hot-Rodding_the_HEI_distributor

Rebuilding a big cap HEI

[Zach079xxx]

My plan is to have the shop install it BUT have someone with brains install it. Once the man I deal with is back in going to run it by and get an A-ok from him that it's right. He built my transmission and engine all in the last 3-4 months. 900 for a 350 turbo rebuild and 2500 for my engine. 1000 labor the rest was parts. I think that was fair, he's a really down to earth guy. Works alone, has no lift; only jack stands and creepers! Just a case of bad timing I guess, but Larry will help me and make sure it's right. The mechanic who fried it did it right in front of the owner, he was holding the timing light.. He turned the distributor over 1/2 turn maybe even 3/4, I thought he was spinning that sucker 360 degrees then poof.

[Zach079xxx]

How come? What else would be the cause? It was totally fine before, I only went to get it timed because the nut came loose and it came out of adjustment. Ran perfect besides the timing not right. Idk I'm going tomorrow to get it fixed

[Zach079xxx]

Tomorrow I'll snap some pictures for sure.. My heart sank when I saw smoke. It puzzles me as well but it happens so not much you can do but move on!

[hatzie]

More How-To on testing the HEI components.

http://forums.hotrod.com/car-craft/7...odule-testing/

BTW you don't want to use dielectric grease between the module and the distributor body... Dielectric grease is an insulator.
Just buy the least expensive thermally conductive grease you can find. It's used on computer CPU to the fan/heatsink... If you've built your own PC you probably already have some. You can find it at BestBuy or Microcenter or even Radio Shack... Microcenter Thermal-Compound-Paste

[cadillac_al]

Originally Posted by hatzie

More How-To on testing the HEI components.

http://forums.hotrod.com/car-craft/7...odule-testing/

BTW you don't want to use dielectric grease between the module and the distributor body... Dielectric grease is an insulator.
Just buy the least expensive thermally conductive grease you can find. It's used on computer CPU to the fan/heatsink... If you've built your own PC you probably already have some. You can find it at BestBuy or Microcenter or even Radio Shack... Microcenter Thermal-Compound-Paste

This has always confounded me. When you buy a new module they include a little packet of ............dialectic grease. I have some heat sink paste for modules but I always question if it is correct or not because the modules always come with dialectic grease. FWIW I haven't had trouble with either one. Lucky again I suppose.

[hatzie]

Originally Posted by cadillac_al

This has always confounded me. When you buy a new module they include a little packet of ............dialectic grease. I have some heat sink paste for modules but I always question if it is correct or not because the modules always come with dialectic grease. FWIW I haven't had trouble with either one. Lucky again I suppose.

I don't get what they're thinking either.
Probably what killed a lot of the 6.5L DS4 Pump Mounted Driver units too. I still have the original PMD my GMC was born with 15 years and 110,000 miles ago. I pulled it off as soon as I bought the truck used in 2003. I re-installed the PMD after I cleaned up a lot of corrosion on the mounting surface...
I used Dow Corning 340 Silicone Thermal Conductive grease instead of that conductive pad Stanadyne used for ease of assembly. The 140Gram tube is a lifetime supply. Kinda like my tube of Sil-Glyde for hoses etc. The $2 packets you can get at Best Buy are probably enough for 2 ignition modules...

[Zach079xxx]

What's the pun behind that? Lol they give you a packet with your order yet it's no good for it.

Originally Posted by hatzie

More How-To on testing the HEI components.

http://forums.hotrod.com/car-craft/7...odule-testing/

BTW you don't want to use dielectric grease between the module and the distributor body... Dielectric grease is an insulator.
Just buy the least expensive thermally conductive grease you can find. It's used on computer CPU to the fan/heatsink... If you've built your own PC you probably already have some. You can find it at BestBuy or Microcenter or even Radio Shack... Microcenter Thermal-Compound-Paste

[Zach079xxx]

Well here I am. Ordered my new MSD 2 days ago, it arrives today. UPS showed up around 3, once it was here I ran it up to the shop. By 5 it was done and I was truckin' on home. As soon as I turned the key BAM it fired right up, I was used to my old cranking over a few seconds then firing. I was impressed. The timing is still off, I can tell it has hesitation and going up hills was awful on the way home. SO heres my plan just like I planned the whole time, once the man is back in town who built my old faithful, I am going to run it by and get everything adjusted out. STILL, I am impressed with MSD and I can't wait to see how she runs once its tuned right. My thumpr cam is making it such a hassle with that shop, thats why the man who built it and tuned it originally will get it fixed right. From now on, you can be dang sure I will be checking that nut holding the dizzy!

My old distributor has black on it and tomorrow or whenever, I am going to pull it apart and see if its noticeable what happened. You can surely smell something burnt when you smell it. Oh well, you learn you move on.

The ONLY complaint I have so far about the MSD is cosmetic; the dust cover for the coil is black. I will most likely be painting that red just to make it all match. One other thing is that the cover that snaps on the top to secure the plugs isn't included, or atleast it wasn't for me. I'll just paint my old one and use it.

Well my post is done, happy with the MSD and can't wait to run it when I'm tuned!

[hatzie]

Originally Posted by Zach079xxx

My old distributor has black on it and tomorrow or whenever, I am going to pull it apart and see if its noticeable what happened. You can surely smell something burnt when you smell it. Oh well, you learn you move on.

Good to hear you got her running.... MSD is a quality unit.

I'd be interested to see where the smoke came out on the stock unit...

[Zach079xxx]

Well, here you go. The picture speaks for itself. Not quite what I was expecting at all.

Look at the Orange wire



Look at the Orange wire again, or I should say casing! The wire is gone!



What had to have happened is he turned the dizzy so far that it pulled the wire wrong and then here as shown above, is what you get!

Originally Posted by hatzie

Good to hear you got her running.... MSD is a quality unit.

I'd be interested to see where the smoke came out on the stock unit...

[68c10owner]

Originally Posted by Zach079xxx

Well, here you go. The picture speaks for itself. Not quite what I was expecting at all.

Look at the Orange wire



Look at the Orange wire again, or I should say casing! The wire is gone!



What had to have happened is he turned the dizzy so far that it pulled the wire wrong and then here as shown above, is what you get!

Thats not good but thats not from turing the distributor too much. That is attached to the distributor body so it moves right along with it. It looks like old age. The wire grounded out and smoked the module probably. Is the MSD in?

[Zach079xxx]

Yes the MSD is in. I love it from what I can tell so far. Starts right up before I would crank over atleast 5 seconds before it fired and all the guts were less than 6 months old. The coil went out and left me stranded and had to be towed. But that's the old one. Timing is still off it sputters and has hesitation. That'll be fixed when my builder is back. So yeah! Pretty excited.

But the other end has a connector, I think him turning it pulled the slack and did something. Who knows, I'm probably wrong.

Originally Posted by 68c10owner

Thats not good but thats not from turing the distributor too much. That is attached to the distributor body so it moves right along with it. It looks like old age. The wire grounded out and smoked the module probably. Is the MSD in?

[enaberif]

Something came through the cap and fried that.

[Zach079xxx]

Look how my day was! I was making a run to the scrapyard to toss an old microwave and cans, literally 500 feet from making it and it shuts off. I coast and pull over and try to restart it cranks but no fire. Oh, you could imagine how livid I was. I'm not a man that cusses but I had a few running through my head at that point. 45 bucks to tow it to Larry to be worked on Monday. That other garage won't even have the chance to LOOK at my truck anymore. Tempted to return the MSD if they'll allow me to and repair my old dizzy knowing now what it is that's wrong. Atleast the man towing knows what brand to go with! That brightened my day

[Zach079xxx]

Well I wanted to finish the thread up in case someone was wondering or for future reference what happened. As you know, it failed on me and it was towed to Larry the man who built my engine, and he dug into it. Clearly the timing was off, which he fixed. And the way the other garage wired it up was incorrect. Their wiring came loose and that's the reason for me being stranded. The distributor is running great again and the overall truck runs like new. Well, I learned a lot on this "quest" lol I recommend the street fire dizzy to anyone, it burns hotter and I can tell a difference.