EC74

74 L48 350 4sp, holley 750 carb, have noticed occasional backfire thru carb when starting from a stop on an uphill. Seems to be only when car is facing uphill, not when starting from stop on level.
Car had been running fine, nothing changed or replaced before this started. otherwise car seems to run fine slow or fast.
Car is new to me, do not know how old the plugs, points, wires etc. are. Any help appreciated.

Super6

Sounds like it's going lean as the throttle is opened with the load of accelerating uphill on the engine. Float level could be somewhat low to start to with, although going up hill would effectively increase the float level.

Jack Wood

Insufficient fuel shot will cause a stumble and/or backfire. Ignition timing under a load can maybe too but probably the accelerator pump on the carburetor is your issue, I believe it can be adjusted. Going uphil from a start is a big load on the engine. Downhill is not as long as gravity still works.

toddalin

Or float level is too high letting some raw fuel slosh over into the manifold. This is then what back fires.

My Holley has no choke and back fires plenty when I flood it out to start it and until it warms up. Sounds like a similar situation.

Open the site plugs with the car idling on a level surface and the fuel should just be to the bottom of the opening barely dribbling out.

Satoa

Yes float level - also for future ref advanced timing will cause carb backfire - could be a small combo of both