Ok, so I'm 98% done with my frame-off resto on my '60 F-250 4x4 with 292 and 4 speed T98 and I have run into a wall.

I broke the engine in with the body off a bit over a year ago and it ran great. I'm in the last stage of the rebuild and trying to get the motor tuned but I've had a bad misfire issue since trying to run the truck for the last 3 weeks.

A little background: the motor is mostly stock with a stock dizzy with Pertronix Ignitor 2 electronic ignition, Pertronix Flamethrower 3 coil. Brand new plugs, brand new wires, completely rebuilt top and bottom end and carburetor.

The problem: the motor starts immediately but has a pretty bad intermittent misfire. To the point that the when you try and drive it, it backfires big time (it's not firing and dumping unburnt fuel into the exhaust) it's especially bad under load.

Here is where it gets weird, if you put the timing lot on the distributor end of the wires, each cylinder fires consistently and without misfire. If you put the timing lot on the plug end of the wires it misfires like crazy on all cylinders.

But, if you run a wire over the top of the motor (isolating it from all contact with other wires) that cylinder quits misfiring and runs right.

So I have arcing between my spark plugs, right? Not so fast.

I replaced the wires (again) and made certain that I had wire separators between each wire on every turn they made from the plugs to the distributor and this solved the misfiring problem on one bank (passenger side). The other bank continues to misfire even though all wires are separated from each other and the block.

In addition I have replaced the coil with a stock coil (no change).

At this point I'm out of ideas. I'm seemingly still getting shorting between wires but I don't see how I could separate them better (and there are no visible arcs with the lights out).

Anyone seen this before and/or have some sage advice for a very frustrated person?

 

That is weird! No idea ... are you using solid core wires? I know lots of people use them with Pertronix, but they are supposed to be incompatible with electronic type ignition. Sure it's not some weird ground issue?

Did you paint everything up... Frame up restoration certainly would seem so. Maybe something that needs a solid ground isn't getting it. WAG though. Try grounding the distributor body with a jumper directly to battery ground.

 

Everything is painted up but everything is grounded as well. Battery grounds to block, dizzy grounds to block (obviously, through the mount) and also a second ground wire to one of the heads. Head is grounded to the body as well (shouldn't have anything to do with this).

I'm at a pretty big loss here

 

And check for arc's not just with the lights out but at night with the lights out (if you have any windows in the garage) ideally you want total darkness.

Also I would try a set of new plugs. Had similar issue once that drove me nuts until I tried a different brand of plugs and that solved the problem.

 

It's supposed to, that's why I asked about paint.

Is it arcing visibly (at night/dark garage) across the towers at the distributor cap? Or somewhere else? Gotta be arcing somewhere. I had that problem with my Y, it's a point style distributor and modern electronic ignition (well pertronix anyway) is a bit hotter. It was arcing between towers and causing a stumble at idle. Stuffed some dielectric grease in the boots and the problem went away. Remember electricity will take the easiest path so the goal is to make the plug gap be that path. For some reason there is a problem there. New plugs might help if they are really old/fouled/worn but you sound pretty meticulous.

 

I had basically the identical issue Nate is having is. I did a tune up the usual cap, rotor, wires, plugs, the vehicle ran great for 2 weeks then started misfiring and even cross firing. The end result was after replacing the wires cap and rotor and plugs once again with varying degrees success, it was not solved. I was at my wits end and was pulling my hair out. I finally replaced the plugs with a different brand and it was fixed, tried it with all the original new wires cap and rotor and the new brand of plugs and it ran fine, put the pre tune up plugs in and it ran fine, Put the original new plugs in and it misfired.
Needless to say I have never bought that brand of plugs again.

It was the first time I had even seen anything like that. So do not rule out the plugs, just cause they look good and are new does not preclude them from being faulty.

I was surprised really, cause how the hell do you send faulty spark plugs out the door?

 

I didn't want to name names, but I've heard quite a few guys say too that they won't run them in anything. Sad.

 

Thanks for the replies.

To answer a few questions:

I'm not using solid core (stranded) plug wires. These are Belden premium wires from Napa (they're the only wire available in town).

I did look for arcing at night with all the lights off and saw none.

Everything is well grounded. I went through and made certain things were really well grounded to include the dizzy, etc.

I have not tried to replace plugs yet. Not sure what brand you guys are having issues with but I struggle to see how plugs are the issue. Unless the misfire is due to some sort of carbon tracking (which I have seen no evidence of) I doubt the plugs are the problem. But, hey, it's worth a try.

 

If they are defective, this would cause a problem. Pretty rare, but you're pretty far off the trail already pard lol.

That's really strange. Phasing? Is this a standard Motorcraft points distributor ... have you tried a new or different cap? Carbon tracking or maybe cracked .. Just thinking outloud.

It may be the distributor cap can't handle the higher voltage of the Pertronix. Note when the switch was made to high energy ignition the diameter of distributor and therefore spacing became much larger, on account of crossfire.

You might try reinstalling points and condenser for test purposes. Also, what are plugs gapped? Try actual spec for 292 or no more than .035".

 

Interesting issue, I am sure it is frustrating! If it were mine I would do the following in this order. Start and observe after each one.
1) Make sure the wires from the distributor to the coil are protected, I would put them in a wire sleeve to ensure they can't ground. Double check the inside of the distributor that there is no grounding as it rotates.
2) I would replace the plug wires but you said you did already.
2) Put dielectric grease on all plug boots, coil and cap.
3) Replace the cap and rotor, today's quality of these parts suck, could be arcing inside.
4) I would replace the spark plugs.

I run a Pertronix electronic ignition and coil in my 292. I bought them in 2006 so they are likely an older version. They still work great.

 

Thanks for replying. I've replaced the coil twice, cap twice, rotor twice, wires twice, and plugs once. The only thing I haven't replaced is the Pertronix ignition module itself.

I called up Pertronix today and had a 20 minute chat with their help line. The man there suggested I try running the power to the coil through a relay rather than from the ignition switch itself. His thought was the ignition switch may not be delivering a clean enough signal to power the coil and ignition module. Even though I already checked voltage running at the coil positive, he thought I could be getting drops in voltage bad enough to cause the ignition to fire late, effectively causing a miss.

I'll try that and report back. Not much hope though.

 

Might just run a jumper directly from the battery to the positive side and see if that does any good. Would be the same as the relay idea.