Hi- This weekend I was having some carburetor "boiling" and vapor lock issues with my 74 F350, stock 460 w/4bbl motocraft carb. While I was waiting for the boiling/perculating to stop and cool down, I noticed that the stock Motorcraft ignition module and coil were VERY hot to the touch. I had driven it about 20 miles, when I stopped, and it was probably around 68 degrees out.

Is the module and coil supposed to get this hot to where you can barely touch it, after 20 miles? This is the first dentside w/Duraspark module that I have owned so I don't have anything to compare to?

Thanks,

 

They should both be hot to the touch, but not so hot that you cannot keep your finger on them. Of course, how you define "too hot" in terms of touch is a relative term.

As a sanity check, you can measure your coil primary winding resistance (resistance across the two smaller terminals with the coil disconnected) - if it's less than an ohm (including meter resistance) than it can potentially let the ignition module pull too much current. This can also happen if the ballast resistor upstream is bypassed. Either results in excessive heat dissipation.

Realize though that the ignition coil will be hot to the touch because it bolts directly to the engine. The ignition module will be hot because it's in the engine bay as well - however, it will be warmer than its surroundings because it dumps current to ground through a power transistor which uses the case as thermal relief.

 

Thanks FMC400. Your response is what I was expecting but just wasn't sure. Now I know and I can do further testing to check.

Thanks!

 

Stacking 4-5 washers under each mounting screw lifts the module away from the fender, promoting better air flow, heat dissipation and longer module life.

 

That is a good idea. I am gong to be upgrading my ignition and distributor so I will keep that in mind when I mount the module. Thanks,

 

I have also drilled some 1/2" holes into the inner fender behind the module to allow cooler air from the fenderwell to reach the back of the module. It seemed to help a lot.