'72 F250 hard crank / rough run / run-on...

[UH60L]

So, I've been using my '72 F250 as a daily driver for over 3 years now with no major issues. It's a F250 custom, 360, automatic. Since I got it I've rebuilt the carb, replaced the battery, replaced the fuel pump, new plugs, wires, cap & rotor. I yanked to points last year and dropped a Pertronix kit in the distributor. Had to adjust the timing a little on the advanced side, but otherwise seemed to run like a cheeta!

Over the last 3 or 4 months I've noticed it would, when the engine was warm, not want to crank. Not from a lack of power but it would just go really slow and fight itself at first, then crank over and start.

Then in addition to that, over the last 2 to 3 months it started doing the run-on thing once in a while when I shut it off.

Now, over the last month or so, sometimes when I accelerate, it almost feels like I'm running on 7 cylinders.

The starting thing felt like timing, and I made a very teeny slight adjustment to the advanced direction. That seemed to help for the first couple days but now it seems to be getting worse, running-on almost every time I shut it off.

The carb is the factory original from '72, so it may be in need of retirement / repair. Also, my exhaust manifold gaskets are shot, and I've been told that can have negative effects on certain things.

Any thoughts would be appreciated.

Clint


P.S.: Someone mentioned to me that the run-oncan be caused by running too low of octane fuel. Pretty sure these trucks were designed to run on regular and that's what I usually run, but could that be a problem with having the pertronix kit isntalled?

[sideoilerfe]

Sounds like the timing is advanced too far. It should be around 10 degrees before TDC. They run better there than 4 degrees which is what the factory setting is. I would start there. Welcome to the forum!

[colnago]

P.S.: Someone mentioned to me that the run-on can be caused by running too low of octane fuel. Pretty sure these trucks were designed to run on regular and that's what I usually run, but could that be a problem with having the pertronix kit isntalled?

Just remember that these trucks were designed and built 50-ish years ago, and that fuel/oil were quite different than what we get now. Remember the good old days, when we had "regular" and "unleaded?" Now, it's all unleaded.

Joseph

[UH60L]

Sounds like the timing is advanced too far. It should be around 10 degrees before TDC. They run better there than 4 degrees which is what the factory setting is. I would start there. Welcome to the forum!

Well, when I put the pertronix kit in the distributor, most of the people I talked to stated that I would need to run it advanced more than normal. During the initial adjustment after install it didn't seem to run right at 10, so I put it at roughly 12. It seemed to run fine for most of a year. Drove it from Salem Oregon to Travis Air Force Base in California and back, with no issues, passing 18 wheelers going uphill doing 75 mph (or more a couple times, didn't know the old girl would go that fast, hehe).

I guess I'll try backing it down a hair and see...

[fastEdsel]

A tired timing chain can also give some "all of a sudden" grief as well. There are a couple good ways to check it and they are listed by the good folks who contribute to this site. I run Pertonix in my FE's as well, I have my Edsel set at 9* BTC idling with the vacuum line blocked off and it runs great. I am also at 3500' above sea level so that can be a concern as well. Let us know what you find.