The Stovebolt Site Forums The Shop Area Engine Shop HEI coil wiring question.

Install HEI distributor and install directions tell to use a #10 wire to + side of coil. Is that direct from battery? My old wiring on the positive side was coming from wire back thru firewall. Any help appreciated.

57thekid,

That wire must be from the key switch, not the battery. The wire is only powered when the truck is running, just like the original coil wire. When the key is ON, the wire is ON!

Stuart

Sounds like I will need to run #10 wire from battery to key switch and back to coil then.

I've read about this heavy 10 wire,is it to prevent harmonics or something? Does the stock GM car or truck with a factory HEI use a number 10 wire? Probably not.Seen many HEI conversions with a typical #14 wire and no one seems to have any problems.

I tie into the pink wire on the back of the ign. switch with 12 gauge. Works fine.

Ran wire from ignition b slot on fuse block. Truck started hard then ran real rough. I ran out of time for the day. Guessing I am way off on timing, and will check tomorrow.

Here's what I found a few months ago when the subject came up on another board. Wire size, I googled it and MSD has a nice article on HEI coils. GM factory coils standard will draw about 4 amps, some better factory coils will 5.5 plus. The amperage draw is a limitation of the coil and module. There are performance coils that will draw 8 amps. The wire industry recommends as a "rule of thumb" 9.3 amps with 12 awg and 15 amps with 10 awg. 12 awg leaves some margin, 10 awg should work for the best coil you can find.

http://www.chevytalk.org/fusionbb/showtopic.php?tid/181240/post/1357867/hl//fromsearch/1/#1357867

Larry

Wow..lots of ampacity charts out there. 10 gauge wire should easily handle 30 amps and usually much more. 12 gauge is real safe to at least 20 amps. If your coil is only drawing 6 amps, it sure seems like overkill to stick a giant 10 gauge wire on it.

On the GM HEI with the .250 tabs, I'll bet you couldn't even find a .250 female push-on that would fit into the cap and accept a 10 gauge wire. This would be a 'yellow' colored crimp connector, and they are fatties!

Hope this isn't BS!

Stuart

Stuart I kind of agree with you on the wire capacity. MSD mention under what condition the coil draws the most, but I couldn't find it again. I find that MSD makes an HEI coil that draws 20 amps;

http://www.msdignition.com/dist_82.htm

My experience has been that the larger wire needs to go all the way to the ignition switch. When I originally installed the HEI in my truck, I didn't go to the switch, only to the fire wall. 8-( I drove that way for 5 years. I installed my rebuilt 292 the wire from the firewall to the switch smoked in less than 300 miles, why?? more compression? evidently something caused the HEI to draw more.

The 10awg will barely fit in the factory .250 tabs, so I usually solder them as well.

Larry

All I know is the directions that came with the distributor stated you MUST run #10 wire. They even had it underlined. I bought the distributor and coil from Jim Carters. Oh well, I ran and hooked up the wire no problem. Know I just have to get the timing right.