I still stand by what I said. I've seen the improvement and better reliability first hand.

I've been a Jeep dealership all areas-Level 4 Master Tech specializing in tune ups, emissions issues, driveability and electrical; ASE (A-1 to A8 + L1) Master multi-recertified tech, and CA certified smog technician since the early '90s and I understand ignition theory quite well. Rich mixtures, especially those that don't quite wet the plugs, are harder to fire than proper mixtures and require more voltage to light. Leaner mixtures are even harder to fire as I stated in an earlier post. The larger gaps permissable with the higher voltage FACTORY TFI coil will fire leaner mixtures better than smaller gaps with the can coil will. Almost any newer model car with that I can think of runs at least .044" gap, if not much more as opposed to the .035" gap that's stock on older Jeeps. Why do you think that is? Why did they go to .035" gap from the .025 gap on the points cars? The larger gap with higher potential voltage capability to fire it reliably IMPROVED the driveability, emissions, power and fuel economy! Yes, as I stated earlier, if your rig is currently running properly, and you don't ever operate it with deteriorated parts, or with extra-ordinary demands and you don't mind re-tuning it every time it misfires, you will see little improvement in emissions, power fuel economy. If you want your parts to be more modern, with longer service intervals between maintenance, and you don't mind opening the gaps to take advantage of the greater potential, you will see an improvement over the life of the parts. If they last twice as long between services, maintaining the designed power, emissions and economy that's an improvement, right?

For those people that don't change their plugs as often as they should, the higher voltage, larger cap, thicker silicone wires can handle the higher voltages needed when the plugs are worn, without misfiring. I recently tuned up a '89 Ford 5.0l truck at work that had 100k on the stock plugs and original wires (both dated '89), with gaps worn to .080" (from .045") and not have a misfire or driveability issue. (I'm catching up on alot of overdue maintenance at the fleet I'm working for now <img src="/forums/images/graemlins/rolleyes.gif" alt="" /> ).

Crossfire can come from the advance curve and is accentuated by any distributor indexing errors. (TSB's for small cap 4.0l Jeeps with crossfire issues show you how to check and correct the indexing). Factory Mopar EFI is not HEI but it does use the better plug type terminal, but with the old type 7mm wire jackets. Higher voltages possible with the FACTORY TFI COIL will make crossfire more likely if used with a narrow cap. Yes, I agree the main reason for the wider cap was to prevent crossfire. The wider cap has less chance of allowing crossfire from that point, as you correctly stated. The better insulated, thicker, wires also induce less voltage that can cause crossfireing external to the distributor. Any crossfire results in at least bad misfire or backfire, or worst case a broken piston. So you agree that this is an IMPROVEMENT to the old parts, right?

The added reliability from the new style cap comes from the spark plug style connections. As opposed to the old style, 1930s design terminal wells in the caps that tend to trap moisture, build corrosion and sieze to the wire terminals if they don't fall out on their own. An improvement, right? I don't see ANY modern vehicles with the old wire terminal wells in their coils (Most don't even run a distributor anymore) There must have been a reason, right?

The TFI coil is not even necessary to perform most of the reliability upgrade, In fact, the wide cap '82 300 Ford truck six spec'd out the same regular can type coil as the '80's Jeep 258, even the same Motorcraft part number. Wire sets for the 300 Ford (and some brands of the V8 sets) come with coil wires for either the can coil or the TFI coil. (later 300's went to the TFI coil with a spark plug type terminal, same low RPM engine).

The main benefit from running the TFI/HEI coil is the larger possible plug gaps ability to fire leaner mixtures This is the reason Ford and GM invested MILLIONS in new design ignition systems, to fire leaner mixtures more reliably (AT LOW, street RPMS), reducing emissions and adding fuel economy. Remember that the '80s were when the new mandated economy standards came into being, along with much stricter emissions standards. The manufacturers also had to warranty that the car would pass emissions without ANY maintanence for a very long period compared to the old days.

The Ford TFI coil costs a couple bucks less (new, in the same grade of parts) than the old can coil.

Factory Ford type silicone jacketed 8mm wires with silicone boots will last much longer than the original AMC/Jeep 7mm black wires, especially with high underhood heat and in moist salt air environments, such as we have here on the coast. The old wires' jackets and boots deteriorate much faster to the point that on a moist morning, or after driving through a puddle, they allow voltage to leak and cause a misfire or stall if the coil wire is involved. Yes, both wires will arc out if deteriorated, it's just that the better wires don't deteriorate nearly as fast! An improvement, right? Especially since the usually only cost a couple bucks more than the black wires, and are usually cheaper and more readily available in "resume speed Iowa" than aftermarket silicone sets made for the AMC/Jeep engines.

All that said, I don't even like Fords! <img src="/forums/images/graemlins/patriot.gif" alt="" />

I'm hittin' the rack, good night <img src="/forums/images/graemlins/sleeping.gif" alt="" />