My first thought is a stretched-out timing chain.

 

X2
set the motor on TDC remove distributor cap.
now turn the crank by hand till the rotor starts to move. Then turn crank in other direction and note how much it turns before the rotor does should not be more than about 2 to 4 degrees.
Dave - - - -

 

 

 

Duraspark II is a good system. First you should check whether you ever have any problems with your distributor. Check for side to side movement in the shaft, this indicated worn out bushings needing replacement. Also check that the mechanical advance operates smoothly and full returns to the same position each time. Mechanical advance is easy to clean and lubricate to ensure proper operation.

 

 

I just disassembled my '84 302 with only 36,000 miles on it, and the timing chain was so sloppy it looked like it would fall off...lol. However, I had checked the timing and it was nice and steady, so I don't know what to tell ya. My distributor shaft seems nice and tight, and everything inside the distributor appeared to be properly intact.

 

An 84 engine? You should have the DSII in there now, no?

103K miles...yes, I would say the timing chain would have some play in it......

 

You have Duraspark II, evaluate condition of the distributor and rebuild if necessary. Recurve it to optimize power and economy, from the factory mechanical advance tends to come in pretty late.

 

 

 

 

 

Not sure what you consider too expensive, but if I was going to spend the extra coin on an aftermarket 302 distributor, I'd look at a custom curved unit from Performance Distributors:

Ford Duraspark - Performance Distributors Performance Distributors

You'll have to select your engine in the drop-down box.

Otherwise, there are a lot of options. The Pertronix ones have come up in a lot of my searches...not for trucks necessarily, but on old cars.

I'm just going through the process of upgrading my '84 302, same as you are. GT40 heads, 4bbl Edelbrock intake, Holley carb, Comp Cams full kit, headers, etc. I mulled over the distributor for quite a while, and in the end I decided to just order a stock reman unit from RockAuto, and the Crane Cams advance re-curve kit from Jegs.

This thing was supposed to be kind of a budget build, so I've been struggling to keep the costs down...lol. My truck is going to see very little use, and when it does get used, it will just be cruising, never hauling anything more than it's own weight. I think a performance distributor would be overkill for what I'm doing, so I just stayed stock but will re-curve the advance for performance.

If I was going to step up from here, I was going to go with one of those custom curved Performance Distributors.