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

Engine, ignition, fuel, cooling, exhaust

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UH60L
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'72 F250 hard crank / rough run / run-on...

Post by 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?
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sideoilerfe
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Re: '72 F250 hard crank / rough run / run-on...

Post by 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! :wel:
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colnago
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Re: '72 F250 hard crank / rough run / run-on...

Post by colnago »

UH60L wrote: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
"Sugar", my 1967 Ford F250 2WD Camper Special, 352FE, Ford iron "T" Intake with 1405 Edelbrock, Duraspark II Ignition, C6 transmission, front disc brake conversion.
UH60L
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Re: '72 F250 hard crank / rough run / run-on...

Post by UH60L »

sideoilerfe wrote: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! :wel:
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...
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Re: '72 F250 hard crank / rough run / run-on...

Post by fastEdsel »

A tired timing chain can also give some "all of a sudden" grief as well. :cuss: 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. :thup:
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