did a complete rebuild on a 258 with a 4.0 head and a weber 38. havent got it running yet. did the tfi upgrade and the resistance wire got really hot with just the ignition on (not running). put in 12 gauge wire in place of the resistance wire and now the coil gets warm with the ignition on. any ideas?

thanks,

mjXIII

I do believe you are supposed to have about 9 volts or so coming out of the ceramic resistor or in your case a wire. I am not sure if the difference between 9 and 12 volts is enough to make a difference in how hot the coil gets, but on my TFI setup with a inline resistor, the coil doesn't get hot with key on, engine off.

Do you have all connections made up correctly??

Here is a TFI Diag Leadfoot's Page

thanks for the diagram. im gonna get under the hood right now...

mjXIII

FWIW, my coil gets hot with key on engine off. (TFI)

I'm not really sure you can just put a 12 ga. wire in place of the resistor wire. I think the stock wire had something like 1.35 ohms of resistance. If you check out some of TRs old posts, he had a part # for a wire that would give the correct resistance. It was for auto zone for a ford pick-up. going by memory I think it was wells F179, but don't quote me on that. do a search.

Uh, you do know that that drop in voltage had to go somewhere, don't you? That whole conservation of energy thing. The difference in voltage got transformed to heat.

not sure if you were aiming this at me or not.... I wasn't meaning to say my coil didn't get warm at all, just not "hot". It does get warm, but no warmer than any other coil Ive had. I was thinking when he said hot that he meant maybe hotter than normal??

As for that conservation of energy thing, its just a little thing..... [img]images/graemlins/smile.gif[/img] Physics was probably one of my favorite college classes, learned about all sorts of cool stuff. Things like spherical moose and cows and such [img]images/graemlins/laugh.gif[/img]

You can't just replace the resistor wire with a piece of 12gauge. The coil is designed to operate at a below 12v. I believe is needs like 8-9v. The resistor wire reduces the voltage to the coil. It's perfectly normal for the resister wire to get warm.

You can plan on replacing that coil about 20 times a year if you run it at 12V all the time. Use the resistance wire, or wire in an old style ceramic shielded resistor to give the coil 8-9V.

TFI coils want 12 volts!!!!!! CJ coils (the canister style) wanted the resistor wire.