I posted this in the dentside forum but thought I might have better luck here since this is 460 specific...

I have a 1976 F350 crew cab with a 460. It has the C6 and 59,000 original miles. Last summer, I started having a problem when it was hot outside and the truck had been driven for quite a while. It would start missing at cruising speed then I couldn't accelerate. If I tried it would miss and backfire out the exhaust. I could idle it home or gain a little speed feathering the throttle. It was very intermittant and I tried testing different things but nothing showed an issue.
I replaced the fuel pump and tested it to be a constant 6PSI. All the fuel lines are only 2 years old. Fuel filter is new.
I replaced the coil as it seemed really hot when the truck was acting up.
I replaced the 36 year old distributor to rule out the pickup. This made a positive difference in how smooth it ran. Timing is set to 12 degrees.
The plugs are new as are the cap, rotor and plug wires.

This spring, I started driving the truck and it has been working great except for the POS 4350 carb. A couple weeks ago, I replaced the carb with a new Edelbrock 600. The truck has been running awesome! It has good power, idles very smooth, reasonable mileage. (LOL!)

That is until this morning. Driving to work it acted up again. I limped it back home. It is only 0 C here this morning! Before the issue only showed up when it was hot outside and the truck had been ran for quite some time. Now it acted up when it is cold out and the engine had just gotten up to operating temp. Once home I verified the choke was open and I tested the fuel flow. Seemed to be good volume and it was 6PSI.

Anyone have some ideas? Ignition module maybe? A lot of the parts I replaced I wanted to anyway since they are pretty cheap. When I bought this truck, I believe it was mostly original. The plug wires even had 1976 on them!

 

Someone with more knowledge should chime in, but the ignition module might be a good part to swap out. Though a little different my '94 was doing something similar when I bought it, and the ignition module fixed it up. Never hurts to do the cap & rotor, gap or replace the spark plugs, maybe fresh plug wires. My other vehicles have all ran stronger with wires every 50k miles and plugs every 30k or more often.

 

Let me ask one quick question, did you keep the original air filter system or use a low restriction aftermarket one? At 0 C you could be getting carburetor icing, my 86 with the Holley 4180 would do it, mostly at idle until it completely warmed up. My 58 with a 223 6cyl would ice up the old Holley one barrel till it would barely run. Pull over cut it off wait a couple of minutes then drive on.