Hello, I've been lurking here for a while and need some help. A few years ago I picked up a 1972 f250 2wd to tinker with and just to have a truck around. It's a 360/C6 and sometimes it runs very good, other times it seems like it is running on 4 or 5 cylinders and has no power. A couple of times when driving and running bad, it has had a little cough through the carb and then runs good. I put a rebuilt carb on it a couple or years ago and have been playing with it over time. I only drive it maybe once a month when I haul something to the dump. If I get this fixed I will be able to start driving it more. Any ideas as to what the problem is?

 

Welcome to FTE

Being a '72 it may still have a points & condenser distributor type ignition system. There are a fair number of "gotchas" with 50 year old ignition components, and simply replacing them with some of the new crap out there today may make things worse, not better. If you don't want to make a career out of it I'd suggest installing a Pertronix Ignitor 1 point replacement module. Make sure the ignition timing advance operates correctly all the way up and down through the RPM range, and the vacuum advance diaphragm isn't blown.

 

I'll check the distributor this weekend. The points are probably gonna stay until I know that they are a problem. I'm trying not to spend money on it unnecessarily. When it is running good, it runs very well for a tired old truck.

 

Make sure the condenser is good, the parts stores sell el-cheapo imported junk.

 

Is it possible to not get imported crap for these, I have same problem with some old tractors. Who makes good reliable ignition parts?

 

Yes, it's possible but the problem is also even good quality or NOS parts can be defective. Most people don't have the equipment to actually test a condenser. A DVOM will measure capacitance pretty well, but that's basically almost useless. So long as it's in the ballpark of 0.22 mfd or micro farads, it will work fine in a V8 or most automotive applications. Can also test for infinite resistance. That is another important test.

Condensers need to be tested at their rated voltage, the coil will "ring" at about 300 volts so they need to be voltage rated even higher than that. So a real capacitor tester will apply say 600 volts DC. And they should be tested at their rated temperature. As in HOT. If you're thinking condensers are more complicated than you thought, you're right. Sorry to get off in the weeds, but this is the problem.

You could try NAPA, and ask for their top of the line (Echlin?) or maybe find a way to buy NOS Motorcraft from a dealer and maybe have them tested for "leakage" or insulation resistance. They still stocked both points and condensers recently. FleaBay is chock full of NOS, but I've gotten duds before.

I've messed around with modern epoxy dipped high voltage poly film capacitors. The Model T guys use similar to these and restuff the wooden box coils with good results. The problem with the NOS or older condensers is they tend to absorb moisture over the years. Even a known good spare condenser carried in the glovebox, should be tested now and then.

Sprague makes a line of high voltage polypropylene film caps, called "orange drops". They used to be made in U.S.A., probably not anymore. There's more to it in selecting one than just the voltage rating and capacitance, for ignition service. This is probably why the el-cheapos crap out right away, if they work at all.

Turns out building a reliable high voltage, high capacitance unit in such a small package is tougher than it looks, at least when they are sold by the pound.

Sprague 716P 0.22uF at 600 volts should hold up, ignition service is tough, though they aren't real expensive, maybe $4 or $5. I got one to fit inside a Ford distributor, but there's nothing that says they can't be used externally. The leads should be potted or somehow protected against vibration or they might break over time from work hardening. I checked it out in the distributor using an ignition oscilloscope and seemed to work well. I built up a spare distributor and keep a couple condensers in the glovebox but I figure an orange drop is practically waterproof and should have a lot better shelf life.

 

Well I replaced the condenser( they're cheep) and checked the points gap and was checking the vacuum advance to see if it worked and discovered that it was connected to the wrong source. I plugged it into the manifold and the truck seems to be working better. Still have a issue with the choke, but I think I'm making progress. Thanks for your help.

 

Well that's the problem today, not the solution. If running a points type ignition top quality ignition parts are critical.