I have a 71 F250 CS with a 390 and I have a problem nobody who has worked on my engine or anybody I've talked to can solve. I'd like to put it before you guys and ask for help from people who really know FEs.

The engine is rebuilt with about 1500 miles on it. It has headers dual exhaust and a petronix module w/petronics coil. The rest is stock. It has a 2bl stock carb.

Here's my problem. It runs perfectly around town. Plenty of oil pressure and a constant 180 degrees. The problems start when I try to pull a grade. Any grade steep or gradual. It reacts exactly the same each and every time. First it starts pinging and gets worse and worse then it starts cutting out as if I were running out of gas untill I have to shut 'er down and call a tow truck. The temp then spikes up to 210 or 220. An hour or so later it will start right back up and run just as if nothing ever happened. (Vapor lock?? If so I don't know what's causing it.)

Here is what I've done to it so far to try and resolve the problem.
1. Replaced the fuel pump twice.
2. Replaced rubber fuel lines from dual tanks and tank switch.
3. Replaced carb.
4. Replaced Petronics module.
5. Replaced coil with matched Petronics brand coil.
6. Switched to premium fuel
7. Replaced distributor.
8. Replaced plugs, wiring, distributor cap, and rotor.
9. Set timing with vacuum gauge.
10. Replaced fuel filter.
11. Pressure tested fuel pump.

Anybody have any ideas??????????
Thanks,
Bill

 

#9 has me concerned. Usually when timing is set with a vacuum gauge it is too advanced. Find TDC on #1 on the compression stroke. Then set the timing with a timing light to 8 degrees BTDC.

If that doesn't work, try increasing the jet size in the carburetor 2 sizes at a time.

It's either too lean or too much timing.

 

I agree, too much timing. Never ever set timing with a vacuum gauge. Timing light only, thats what they are for. I will bet your total mecahnical advance is 38 degrees or better.

 

Thanks guys. I'll try it and get back to you.
Bill

 

Just to clarify one point on what a vacuum gauge is good for setting. They are best when it comes to carburetor tuning. Youn cannot set by ear or any other old fashioned method a carburetor better than using a vacuum gauge. The one thing that is even in the same class is an oxygen sensor. It can tell you how rich or lean the fuel mix is.
Anyway, I just wanted to point this out.

 

9. Set timing with vacuum gauge, you really need a timing light sounds like you are running way to advanced i only run 8 to 12 btdc and no more than 28 total advance

 

I had a vapor lock problem with my 72 F100 the fuel pump had the canister filter on it and it was causing a vapor lock. I switched to a 78 model fuel pump and a inline filter and it fixed the problem. Make sure your timing is correct first.

 

I just wanted to thank you guys who replied to my question. The problem turned out to be a combination of carboration and vac advance. I took it to a carb expert who calls himself "Dr. Carb. He re-jetted the carb because it was WAY to lean and replaced the stock vac advance with an adjustable one then recurved it.

Problem solved and my truck runs perfectly once again.

Thanks again,
Bill

 

Cool!
Just sucks you replaced all those parts with no better reaction. At least you are on the road!