Needing help and has nothing to do with my age!

[Jim Boy]

I posted in another forum but didn't get any response so I'm trying here.
Good day folks. I have a brain burner going on. The story.. 68 truck ran perfectly to the golf course. On the way home it started to backfire on acceleration. I thought it was mad at my score but it continued all the way home. So I thought that with the crappy fuel we have nowadays it must be in the carb. I had a kit so I rebuilt it. Fired up the money pit and it ran perfectly until it got hot and then the same problem occurred. I talked to a few knowledgeable guys and they said carburetor. So another kit and dider again. Same thing, no worky right. So there was two choices. Either beat the heck out of this money pit or be nice and spend some money on way overdo items. So I chose the latter and did a lot. It got new points and condenser, new coil I had in a box on the shelf, plugs and timing done. I even replaced the carb that c/w automatic choke for my old one from another engine that c/w manual choke, that engine ran perfectly. Same result.
So the 250 engine is idling for quite awhile while I'm standing there reading about the different needle movements on a vacuum gauge, when the engine just chugged a couple times and quit. We stared at each other for a while as I was not going to let it win. I figured that it ran out of gas from the carb. I took the top of the Rochester Monojet off and when I lifted it up the gas gurgled into the fuel bowl. Now, I'm a thinkin that I either have a stuck needle valve or my fuel pump is not doing the job after it has ran for a while. When cold, the engine will accelerate like it should but when it gets warm, bingo, bango, no ticky no worky.
That saying of "less is more" doesn't apply to old farts that like to talk(or type) as you probably have noticed. Just trying to eliminate questions. I will treat all replies with great interest and report as to whom is the winner.
Thanks in advance and have a good day eh!

[OLDROCK&ROLLER]

I have found that backfiring is always a ignition problem. Have you checked your vacuum advance and timing.

[raggedjim]

Was the backfire through the carb or the mufflers? If through the carb I'd think timing issues, if through the mufflers I'm thinking unburnt fuel from either running rich or a cylinder not firing.

[68 P.O.S.]

This ^^

[LNP]

If the fuel pump is not pumping efficently when cold the choke will be closed to richin the motor up but once its warm and the fuel supply is crappy its to lean and will run like crap backfire thru the carb etc. Do a couple simple fuel pump test. Check fuel pressure and fuel volume. Fuel volume simply hold a jar with the fuel line poking inside it have someone turn it over or start it up momentarily to see if it is pumping sufficently. Plus now you will have a fuel sample to look at to see if theres water or other crap in your fuel.

[loudchevy]

Originally Posted by LNP

If the fuel pump is not pumping efficently when cold the choke will be closed to richin the motor up but once its warm and the fuel supply is crappy its to lean and will run like crap backfire thru the carb etc. Do a couple simple fuel pump test. Check fuel pressure and fuel volume. Fuel volume simply hold a jar with the fuel line poking inside it have someone turn it over or start it up momentarily to see if it is pumping sufficently. Plus now you will have a fuel sample to look at to see if theres water or other crap in your fuel.

Similar to this suggestion, install a clear plastic fuel filter inline before the carb. I had a similar stalling issue years ago on my blazer, the clear filter would fill up when the truck was started and then slowly the filter had less and less fuel until it would die. Ended up being a cracked rubber fuel hose sucking air.