Backfiring stalling and missing hard starting

[Stewart]

Car until yesterday was running fantastic. Ran smooth and tons of power. First start of the day yesterday it fired off fine ran for a few seconds then quit like someone shut the ignition off. Started it back up and it took a lot of throttle to get it to start and it would run very rough. I gave it a few minutes of warm up and ran well enough to take it on the road to see what would happen. Ran rough and backfired rapidly through the exhaust while accelerating. Stopped after less than a half mile at a store went in and back out in less than 5 minutes hopped back in and it started up instantly like it normally does and then ran perfectly. Later in the day I took it down to Fargo and it ran perfectly all the way there 75 miles or so and for another 20 miles on the return trip then it started to miss slightly for periods of time and then return to running like normal.

This morning it did the same thing but way worse. Didn't really want to start and once it was running it didn't want to stay that way and would stall and then hard to restart. It would backfire out the exhaust rapidly and miss in any gear at any rpm. I had to limp it back to my apartment in first gear to keep the rpm up and the second I pulled it back into my garage and it was like someone flipped a switch and it returned to running normally so I took back off for class and its been running fine since.


Last night I checked and reset the points, new cap, rotor and checked the timing and it was dead on. The only thing I noticed that was slightly weird to me was the mixture adjustment screw on the rear carb was flush with the outside of case as thats what it took to get the mixture correct. Spark plugs are a medium tan.

Setup is
Hif4 carbs
45d4 that was rebuilt by Jeff at advance distributor about 1500 miles ago running points
Lucas sports coil.

 

[jlaird]

Could the needle on that carb be looseish?

 

[RickB]

This sounds so very very familiar...

hmmm... My post with same kind of problem

I also have a new(ish) dizzy from Jeff, I have HS carbs.
Having gone through the fuel delivery side I've concluded it's electrical.
This could be caused by a faulty ignition switch, or many other things on that side. It's going to take a process of elimination to find out what is happening.

 

[Stewart]

I think I have found the problem. The rear carb is suspect at this point and is apart on my desk. The level of the jet was between a 1/16 or 1/32" below the top while the front carb which is dialed in was the opposite above the top.

The big thing I've noticed is the jet is rather sticky. I can adjust it richer but it tends to be sticky and will jump trying to adjust it leaner and it will stick in position unless I push on it lightly.

 

[Stewart]

I wont know till tomorrow morning when its cold out but I think its fixed. Once the jet was freed up and matched with the front carb it only took a half turn on the adjuster to get it in tune. Did a quick test drive it felt good and the plugs are nice and even light tan across the board. On a plus side I think I finally fixed the sticky throttle.

Hopefully when I go to vote tomorrow morning I can take a well running B.

 

[Stewart]

Fired right up this morning on and ran great so hopefully that was the problem.