The Stovebolt Site Forums The Shop Area The Electrical Bay 235 fitted with HEI, how to wire?

afternoon all
i've run a search and can't find anything, so i'm hoping that the knoweldeg base here can help me out.
I have just fitted a 55 I6 235 motor in my 49 chev. This engine came with a HEI fitted.
My old 235 motor had a points ignition, and my wiring loom is still set up for this, with a switched live when I turn the ignition key on. This wire previously fed the coil.
My question being, how do I wire the HEI to to car? Which of the two connections (pink or brown) do I hook up to the switched live?
I've added some pics to shw you the set up I have.
Thanks, Taff
[IMG]http://img444.imageshack.us/img444/8003/22001.jpg[/IMG]
[IMG]http://img379.imageshack.us/img379/4698/22004.jpg[/IMG]
[IMG]http://img379.imageshack.us/img379/3480/22003.jpg[/IMG]
[IMG]http://img79.imageshack.us/img79/4517/22006.jpg[/IMG]

Look at the original wire that supplied the (+) terminal of your point-type coil. It will probably be relatively small in diameter, and have a silvery appearance, not copper. That's because it's a nickel/chrome resistance wire designed to drop the voltage to the coil to approximately 9 volts during normal running. There might also be a second wire attached to the coil that bypasses the resistor during starting. Insulate any and/or all of the wires that were attached to the original coil- - - - -I usually just tape off the terminals and wrap the wires into the harness. Then run a heavy wire, #10 is best, from the "run" position of the ignition switch to the pink wire terminal of the HEI coil. You're good to go- - - -no resistor or bypass wire is needed.
Jerry

Edit: I just noticed you're working on a 1949 model- - - -has it been converted to 12 volts already? The HEI will not work on a 6-volt system!
Jerry

Hi Jerry
good spot! i forgot to mention, I have already upgraded to 12v, 6v is bloody hard work to live with in our damp climate!

there is a custom loom fitted, and it only has one wire running from the ignition switch "run" position, i take it this is the wire I need to hook up to the (+) (pink?) connection on the coil pack?

Yes, but be sure it's heavy enough to carry the current draw of the HEI ignition system. The 50,000+ volt firing voltage is generated by using a coil with a very low primary winding resistance, usually in the range of 1/2 Ohm or so. Before the internal current limiter in the ignition module kicks in at the magnetic saturation point of the coil, it's possible to draw 20 to 30 amps or so through the primary windings. Make sure the supply wire from the battery to the ignition switch and the wire going from the switch to the coil are heavy enough to carry the current without overloading. There's a reason the GM engineers chose #10 wire for the millions of HEI systems they installed as original equipment from the mid-1970's on up.
Jerry

Look at the image you posted that ends in the number 22003. The bottom inside post, next to the valve cover rail needs 12 Volts. The inside post above it is for a tach.
Make sure the tach is compatible with electronic ignitions.
Make sure the 12 V from the ignition has 12 V in both "Start" and "Run" positions.

ALERT !!!!

That HEI with the stock coil will use less than 2 Amps.
That isn't a 10 gauge wire that they used. It's a skinny 13 or a fat 14 gauge with extra thick insulation.

I've measured the resistance of hundreds of HEI coil primary windings. They average around 1/2 Ohm. 14 volts (charging system voltage) divided by 1/2 Ohm, according to Ohm's Law works out to 28 amps. Until the inductive reactance of the coil primary kicks in partway through the coil saturation cycle, there will be a very high primary current. Watching the primary pattern on an oscilloscope is pretty informative, with a heavy current surge early in the coil saturation waveform. Bigger is better on the hot wire to the coil.
Jerry

HEI primary winding is not connected to ground. Primary coil current must pass through a couple of resistors and a Darlington before it reaches ground by way of the module hold down screws.

I have my HEI wired with the original 6 cyl. 1.8 ohm ballast wire. Voltage drop across the ballast is 2 V. With 14 V charging voltage before the ballast, it still has an honest 12 V at the coil.

2V/1.8ohm = 1.1 Amps.

I did at one time temporarily wire a 3 A fuse in the line and the engine started and ran fine without the fuse blowing. I didn't actually drive it because I was just using jumpers.

If the HEI used that much current I would have to get a bigger alternator.
My '67 GMC has the original 37 Amp 10DN with external regulator.
Right now it keeps the battery fully charged and it has to keep up with the HEI, electric radiator fan, Climate Control AC, tecumseh trailer brake controller and small CD stereo.

Different strokes, etc.! I wonder why GM wasted all that money on heavy wire for millions of cars if it wasn't necessary? No wonder they went broke, paying all those incompetent research and development people! All they had to do was log onto the Stovebolt forum and ask for some advice!

Now, where's that sarcasm icon?
Jerry

I have a 63 C20 with a 292. One of the first mods I did was install an HEI, best an easiest mod I've done. I ran 10 awg from coil to firewall, didn't run 10 awg to ignition switch, I knew better. It ran great for 3-4 years. One morning I started it and the wire harness from ignition switch to firewall smoked. I checked for a short and could not find one. It only smoked the one wire and I was able to salvage the harness by replacing the one wire with 10 awg. Your mileage may vary!

Larry

just a quick update. I followed your advice, and she fired up second turn of the key.
Many thanks to all who chipped in with advice, helped me get my baby running again
Thanks, Taff

I'm with Taff's comment. Today, I finally hooked up my old Sun tach with HEI and it worked just like you all said. I have the Landon HEI for the 235/261. No filter or issues with the HEI just hook it up to the coil negative post and it worked just like new.

Thanks everyone.