The cap I install awhile ago I bought thru Summit. Supposed to be for the 352 FE. It "mostly" fit but I had to dremel out more clearance for one of the screws on the Vac Advance.
It never "dropped" on like I felt it should but seemed to work alright. I have experienced from time to tome some secondary ignition breakdown under load and trying to accelerate and I'm trying to make sure all my parts are in good order. Pertronix Ignitor, no resister and a 1.5 ohm coil. New plug wires, rotor and the afore mentioned distributor cap.

Anyway, can anyone recommend where I can get a Distributor cap that is really for our FE motors and will fit without having to trim on it? Lots of places say they do (like Summit MSD-5506) but it ain't always so.

Thanks and hope Christmas was great for y'all here in FTE-land.

 

There shouldn't be a difference in the cap, just the **** poor quality of what we are buying. FE didn't have a different cap from any other V8.

Eric

 

Stick with the Blue Streak caps and copper electrodes.

 

I ran into a situation with the distributor rotor, not the distributor cap. When the federal smog regulations came onto the scene it looks like they changed the length (though not the part #.) Unless you can find really old stock, virtually all the distributor rotors available will be what I call "short" versions. This increases the rotor/terminal gap, and has the same effect as opening up the spark plug gap would, i.e. increasing the firing voltage of the ignition coil by quite a lot.

Not that this is necessarily a bad thing, but, the entire ignition system has to work together as a unit, as a team and it was carefully put together by people who studied all of it together. Points distributors weren't intended to run continuously at the higher voltages that are realized when running (for example) without a ballast resistor.

So can run into a situation where arcing to ground or misfire occurs, esp. if any of the components or wiring isn't up to snuff. I noticed this on very high humidity summer days inside my garage. It was arcing all over the place. I found some old "narrow gap" rotors and everything settled down.

An ignition scope will show excessive ignition coil firing line voltages, it's one of the key ignition metrics to look at during a Tune-Up. Not saying this is "the" problem you are experiencing but I suspect it is pretty common and something to beware of when running aftermarket ignition parts of any sort. Change even one single component and it should run "better", but .. it might not. The way the ignition coil firing voltage is supposed to work, it only rises to a level of voltage necessary to jump the spark plug gap, and no more. This is maybe 10k volts at idle, the rest is held as reserve or overhead, for when the engine is under load or compression, and as the plugs wear and lose sharp edges, lean fuel mixtures etc., then the coil voltage or spark plug voltage requirements increase.

This is something to consider, it might not visibly arc or misfire while you are watching at idle, but what about high speed or high loads pulling up the side of a mountain with a load of gravel? Look carefully inside the distributor cap under a strong light for evidence of carbon tracking, and for etching or half moon tracks around the spring terminal of the rotor. If the firing voltage is excessive it will blast through the rotor itself straight to the distributor shaft. For some reason it didn't like my "crimp your own" universal plug wires either, when running the Pertronix.

Ford Motorcraft carbon core plug wires, and a pre-smog era NOS Autolite black rotor got it purring nicely and looking good on the scope. I also use NGK non-resistor spark plugs, and everything ignition related finally seems to play well together. Jus' Sayin', without a peek on the scope it's kind of a crap shoot!

 

Dizzy cap is the same 1957/74 for all V8's: B7A-12106-A (Motorcraft DH-6)

 

Finally got to install the Blue Streak cap & rotor. Replaced the couple month old MSD cap and rotor. Fitment on the MSD was very tight and took some dremeling. The Blue Streak fit looser but dropped right on. Anyway problem went away. Truck runs great now. I had never heard of Blue Streak before but I am happy now. Thanks Christmas!
I had thought MSD was a safe bet. ☹️

 

Glad it all worked out.

 

And really now, can you have too much blue?

 

Sadly my happiness was short lived. The stumble, which actually sounds like not a misfire but a staccato like sound, more like extra firing going on. So I have replaced dizzy cap, rotor, re gapped the plugs to .045 from .035 and the issue persists. I have a set of summit racing 8mm plug wires that are a couple months old and I am going to wire tie wooden spacers to make sure there isn’t any cross fire going on and see how that goes. I don’t have a scope and the issue only happens sporadically under load and acceleration. Hard one for me to find.

 

Make sure that wires #7 and #8 do not run parallel. Move #7 to the front of the wire clip or, just to see if that's the problem, leave #7 temporarily out of the clip and away from #8.

 

Two tests you might try - the younger guys call them "old school" for some reason.

1. Observe the engine running in total darkness. Any appearance of blue light is the plug-wire juice looking for ground.

2. With engine idling, pull off a plug boot and insert a moistened pinky finger into the boot. Hold it there for a few jolts, observing that the pulse coincides with the expected ignition events. Do this for each of the eight plug wires, mentally comparing the relative intensity and frequency.

If you can complete test #2, you have a weak ignition output, or you are a lot tougher than I am. Or was.

Eric.

 

i Isolated the routing on #8 to get it far away from #7 and it didn’t make any difference. Thanks for the tip.
I also watched the engine/plug wires in the dark garage. No sparking. The truck runs great until I try to accelerate with a load on it. If I take it easy it runs great. On my test after rerouting the #8 wire I get cruising around 35 or doing 3rd press the accelerator and brake and can reproduce the issue easily. Making me rethink vacuum or vacuum advance? I can’t reproduce it in my garage unfortunately. The way the “miss” sometimes sounds like a muffled machine gun makes me thing ignition stuff.

6t6merc, after testing your second suggestion, after I woke up I think I remember the spark felt fine.

 

Sounds like it could be the carb. When did you last go thru it?

 

Any chance the plug wires are out of the correct firing order?

I still think you should spend more time on the ignition. That is a points style distributor after all, and with a full "12 volts" to the coil the secondary output voltage is a lot higher, so the potential for arcing is going to be greater. What coil are you using?

Notice too for example, when solid state ignition came around the terminal spacing was enlarged.

If arcing or misfire is a problem you want to reduce the plug gap, or at least not open it up, in troubleshooting. Idle is pretty easy on the coil firing voltage, it's sometimes only under load that problems can develop. (A real good torture test of the ignition insulation and components with a manual is to "lug" the engine and crawl about 5 or 10 miles an hour in high gear.)

Gap the plugs back to factory spec (to reduce the coil firing voltage) and for test purposes, re-connect the ballast resistor or, a use a 3 ohm coil if you have one would be convenient, or temporarily swap the contact points system back in, etc.

 

To much focus on the ignition. Time to look at other things. Fuel filter, power valve, vacuum leaks, the basic stuff. If it only happens under load tear the carb down and put a kit in it. Not sure what carb you have. But if it's a Holley make sure you get rid of the stone inlet filter. Those things are their own problem.