The Stovebolt Site Forums The Shop Area The Electrical Bay Need Help with a HEI sys.

Ok I am heading to the junkyard on sat to see if I can locate a HEI system for my 68 chevy. Is there a physical difference from my points distributor? I guess what I need to know is what exactly am I looking for?

Thanks in advance

Brad

The distributor will be physically larger at the cap area. The coil is mounted in the top of the distributor cap and is covered by a plastic cover.
Look for a distributor with newer plug wires on it as they are different than the points type wires(ends are different on the cap)
Have you asked around locally to see if anyone has one laying on their bench or shelf?

Ok will go shopping for one this weekend. Also I found a pic of one on the web. Will I need to pull the entire distributor with cap and all or just the top part?

Skokie, You'll need the distributor, cap and sparkplug wires to match the cap. Not to confuse you but there is also an early version of the HEI that does not have the coil in the cap, still the cap is going to be about twice the diameter of the original. Have fun.

Regards,
Larry
63 C20 daily driver

I assume you are using the HEI with a V-8. Most of the time there will be clearance problems with the firewall using the HEI. I ended up having to notch my firewall and I still had problems. The vac advance and wire connector section were about 180 deg apart and both were close to the firewall on each side. I solved that problem by rotating the cap 90 deg relative to the distributor body. That can be done by carefully measuring out and filing a new notch in the distributor body 90 deg (this is the notch that fixes the position of the cap. Now, the wire connector extension on the cap points forward and no more firewall clearance problems. When you are at the salvage yard, make sure you get the two-wire connector that connects to the distributor. Regular slide on connectors can be used but the special connector designed for that distributor works better.

Forgot to mention you do NOT need the ballast resistor with an HEI. Wire the distributor straight to your ignition supply. You may also have a wire that goes from your starter to the points distributor. This wire isn't needed with the HEI. It was used to provide 12v directly to the points distributor during cranking for some added spark intensity. The ballast resistor drops the voltage to the distributor to 8 or 9 volts I think, probably to preserve point life.

Also, get the wiring plug that snaps into the cap. It has the power wire connection. The wire that currently feeds your points won't be big enough, you'll need to replace it with 12 ga. wire plugged into the fused ignition on your fuse panel.

I offer this opinion here even though many of you will not agree with it.
You have a 12volt system, but the charging voltage will be around 14.0 volts. A stock resister wire is 1.4 or 1.8 ohms (if I remember correctly) depending on if it's for a 6 or V8. It will drop the voltage 1-2 volts. This will still give you 12 volts at the distributor and draw only slightly above 1 Amp. Get out your voltmeter, do the math and you'll see that this is correct.
A popular misconception is that you have to use 10-12 gauge wire with a 20 amp fuse. Your stock dash radio uses more current than a HEI. It has a 5 Amp fuse and is wired with 16 gauge.
Your resister wire is the cloth covered wire that goes from the distributor to the firewall bulkhead connector. Just crimp(it won't solder) a new connector on the end and plug it into the HEI. You'll both be very happy.
When I first put the HEI in my 292, I bypassed the resister. The third time I started the truck, the HEI module burned out.
I reconnected the stock ballast resister wire and it's worked just fine for years.
The "nay" sayers will want to tell you that you won't get as hot a spark. Bunk! Nay sayers don't even say nay.

I say "nay"; but whatever works for you, Richard .

Skokie,
I ran a switched, 12 volt fused supply from the fuse block and it was a 12 guage wire.

The fatal mistake is the grease. That's right, the dielectric grease that's under the module? Without it, the module will overheat and fail . If it's been there awhile, clean it off and replace with fresh. If installing a new one, the grease packet is usually in the box.
HEI is a good system, just has a short service life. Don't expect more than 50k miles without needing to replace something.......plugs, wires, coil, cap, rotor and sometimes module. They just burn out.
Always check the advance mechanism....they are usually worn and rusty. Mr. Gasket sells a recurve kit that has all the parts you need to fix it. You don't have to install the aftermarket weights or springs, just the bushings; unless you are running a custom engine or gears out back........That's another subject!

And check the vacuum advance. When I bought my 69 the PO had slapped in a well-used hei. Milage was horrible, so I checked the vacuum advance, it didn't work. Bought a complete upgrade kit with hotter coil and performance module, advance module, springs & weights, cap & rotor. I also found the weights rusted in place, so I had been runniing only 6* advance at speed. Got 9 mpg on a road trip before the upgrade. Now I'm running 42* total advance, and am getting 14 mpg on the highway.

As far as voltage to the hei, they were designed to run anywhere from 11 to 15 volts. I don't know what the output voltage change is within that range, but if your module burnt out it was either a bad module, the voltage regulator was set way to high, dielectric grease hadn't been used or a static field had been introduced to the module. It wouldn't have been the fault of standard voltage. I'm not saying that the module won't last longer on the reduced voltage, it probably will. But it does raise another issue, what will happen if the alternator dies and the voltage at the hei drops to 8 volts? Will the hei have enough spark to run the engine? How about running a test on that, Richard? I'd like to know the results. Also, have you connected a voltmeter to the hei output and compared the voltage differences? This, too, would be interesting to see.

When GM started using HEI's around 1975, I had a failure in a new company truck.The rotor, cap and wires were all burned. The culprit was the spark plugs,the truck went 30,000 miles on the original plugs,the electrodes were almost complety eroded away,yet the truck still ran ok.After that, I always replaced the plugs sooner ,never experiencing another problem at all. The HEI produced so much voltage to fire the worn plugs,it destroyed the wires and cap.

When I was dragracing my Pontiac, I tried all the tricks looking for more power. I wired in a cut out switch for the alternator so it wouldn't charge when racing. At the end of the track just turn it back on. It sound like a good idea till the HEI started to cut out. The battery voltage along wasn't enough to keep it running. It was a 11.0-1 compresson alcohol burning engine but, HEI needs the proper voltage. Thats why GM but 10 or 12 gauge wire to them. And you do need the wire from the starter or a from the start circut of the ignition key. With out it, it will never start. The ignition side (run) of the key switch does not send voltage to the coil in start mode.
Just tie start and run together at the key switch and run a new 10 gauge wire out to the distributor. Shove the stock wires under the dash for the next guy to restore back to original. Joe

If you tie the start and the run wires together you starter will not shut off