I've been battling vapor lock issues on my '84 F-250 with a 460 for awhile now:

https://www.ford-trucks.com/forums/1...l-problem.html

I had planned on replacing the mechanical pump and adding more heat insulation. The pump I ordered is a Carter 60081 which is designed to work on trucks and vans with a 460. When I removed the old pump I discovered it was the '85-'86 style with return nipple on the pressure side. When I put this truck together 15 years ago that was the only pump I could find that would clear the oil filter adapter. This truck was originally a 351W so rather than change the frame saddle I cut a hole in it for clearance. I had capped off the return nipple...completely forgotten about that. The pump I ordered will not clear the oil filter. I'm not sure if I could gain more clearance by turning the adapter down more, but that would require cutting the hole out bigger in the frame saddle which I'd rather not do. I'd prefer to eliminate the return style pump if possible since my truck does not have return lines on it and I'd rather avoid the leak potential of having it capped off. From what I can see the Carter 60081 (which I have) and the 60036 look identical...not sure what the difference is. I don't see any other pumps with the curved inlet line that fit a 460. Question is, will a 302/351W pump fit, or is the eccentric arm different? I haven't looked through those applications yet, just trying to find something that will fit so I can eliminate the return fitting.

 

You could forget the mech pump all together and run some sort of electric pump. If you mounted the elec pump at the rear of the truck it might help your vapor lock problem.

I haven't a clue why the 460's had the vapor lock problems and others didn't. You know if the engineers could save a dollar on each 460 truck they would have. There was a definite reason they put the return system on the 460 trucks, I just can't point to the specific "smoking gun" that caused it. You may have gotten by with it for years, but maybe you were borderline that whole time and now some little thing has thrown you over the edge.

 

I think Dave's suggestion is what I'd do were I in your shoes. Fuel under pressure will have a much better chance of not boiling, and the pump in the rear should be cool enough to work.

Otherwise I think you'll be fighting problems for years.

 

Any good, reliable electric pumps? I've never been impressed with the parts store external pumps, they only seem to last a few years and I've heard the Holley pumps are noisy and tend to run hot. I have dual tanks too so it would have to be mounted ahead of the switching valve.

 

Carter P4070 . Their rotary vane pumps are self regulating and they run a wet motor so no shaft seals to fail like a holley. I have been running them on most everything forever, the one on my IDI was 7 years old when I put it on in 06. Still works perfect.

They are a bit on the loud side but they are very good pumps.