It sounds like you have a mid 90's HO motor (351 firing order), which if that is the case will have a roller cam in it.
Roller cam requires a machined gear on the distributor (as opposed to a cast gear for flat tappet cams).
Doesn't explain how it ran and then didn't but it's maybe worth mentioning.

Also worth noting - I believe that it was 82 that the imbalance on 5.0's changed from 28 to 50 oz. If you have an 81 v/damper or flywheel/flex plate on a later motor, that would cause issues as well.

 

Thank you, 1995XLT. I just went out there to see if there was any difference in that gear between the two distributors(the one that came with the engine and the 1981 model). The gear is the same on both. They sit the same distance from where the distributor is fully seated. The only difference is the length of the shaft from the bottom of the gear down... the '90-something one is a tad longer, but the '81 one sits plenty over the rod.

However, looking at it, this time, I noticed that the one I've been running in it(the '81) has a burnt look to the gear and the teeth seem to be slightly marred. I didn't notice this before. The burnt look, I can't figure out. But, the marring could possibly be from removing it and re-installing it over and over... I dunno.

All this messing with it, I can't even get it to crank, anymore.

 

The 2 gears look the same except on very close inspection, the cast gear (flat tappet) will have a roughness (casting marks) where it isn't machined.
The machined gear for roller cams will have been turned on a lathe and will have no rough parts.

 

I really can't see any difference in them. The 1981 distributor is aftermarket, so would that make a difference in the possibility of it being caste, or machined? I got it when I put this '90-something engine in. And, this may be a silly question, but would it damage the cam so as to kill the engine? Going to figure this issue out and probably feel stupid, afterwards! :P

 

I think my first question should have been: Even though the engine itself is a '90-something I'm using it in an '81 truck and its ignition/firing system. So, would the firing order still be for a '90-something, or would it stay the same as for the old 302?

 

Firing order is determined by the camshaft. If you have the old style 302 cam you will have the old style 302 firing order. If you have the HO cam you will have the HO firing order (HO f/o is the same as 351).
If you had your rocker covers off, you could watch the order of the intake valves opening.
Truck engines (5.0) changed to roller cams in about 92, and changed to HO roller cams in about 94.

 

Thank you, again. 1995XLT.

 

Anyone have a vacuum diagram for only what's needed to make the truck function?

 

It doesn't include the vacuum line for the transmission. This is exactly what was on the sticker under the hood.

Right now, I have the transmission vacuum line going straight to the vacuum tree, the choke connected to the base of the carb where it's always been, and the distributor connected to the front of the base of the carb. Everything else is plugged off. The choke doesn't seem to be functioning properly, though.

 

The timing was not the issue. The distributor was not the issue. The firing order is the same for later model 302's as it is for earlier model 351's. The choke got stuck at the carburetor. No amount of vacuum would open it. I hope this helps anyone else before they tear apart the front of their engine to check their timing chain and gears.