Coil heat soak issue, or bad coil wires x2?

[ram_g]

(Posted on the other forum, posting here too to maximize views...should probably edit my .sig here as I am running a carb'd 302 now...)


I've been chasing a frustrating hot start problem. Car starts and runs fine when cold or if re-started immediately after a stop. If I let it sit for 10-20 minutes it's a beast to re-start.


Earlier I added a spacer under the carb to keep the fuel bowls cool, changed the remote battery wiring from 4 ga to 1 ga, and added a heat shield to the starter. Seemed to improve slightly but then took a turn for the worse - stubborn no-start when hot, massive backfires through the pipes.


So I purchased an inexpensive spark tester (best $10 I've spent recently!) and sure enough, found a weak/intermittent spark from the coil when hot. Replaced the coil (Crane LX-92, originally purchased together with my Crane Hi-6 ignition box and distributor with my Forte engine package) only to find identical behavior from the new coil. So then I tried replacing the coil wire (yes I know, try the cheap fixes first!!) and voila, seemed like I had a fix. But would you believe it, the replacement coil wire (had Davis Livewires, replaced coil wire alone to Taylor brand wire) has the exact same problem - ok when cold, dud when hot. Only my original Ford Racing coil wire seems to work ok (both cold and hot) but I'm wondering if that will last or it too will bite the dust.


So I'm scratching my head on what the heck I have here. It's possible that my coil location (low down on the passenger F panel) (see photos below) is too hot (right below the degas tank, not far from the J-pipe) and somehow that is messing with the coil/wire performance when heat-soaked. Or (since it all seems to work fine with the Ford Racing wire - for now) it may be that both the Livewires and the Taylor coil wires were bad and my original Ford Racing coil wire will remain A-ok.


Suggestions?? Should I take the trouble to move the coil location? See below for a couple of choices - either higher up on the passenger side rail (further away from the exhaust) or attached to the engine block on the driver side via a plate I can fab up - will need to lengthen the coil primary (feed) wire but the secondary to the distributor can be much shorter.


What would you do?


Thanks in advance!


Current location of coil - pass. F-panel below degas tank, not far from exhaust.
http://www.ffcars.com/photopost/data/500/DSC00215.jpg


Possible alternative locations:
http://www.ffcars.com/photopost/data/500/Slide1.jpg

[CraigS]

My gut feeling is that the location is OK. Seems the one at the top of the picture might actually be worse because it's a little further away from the pipe but right over top of the pipe. The front of the left head 'might' be better. I'd probably leave it where it is and add an insulating panel between it and the pipe. You could also try, as an experiment, running your rad fan all the time to have more air moving around the coil.

[edwardb]

I've had zero issues with both of my builds locating the coil on the front of the DS head. Keeps the wires nice and short, and heat shouldn't be an issue. I think it's a pretty ideal location. Many use it. I know some guys worry about the vibration. Hasn't been a problem (yet).