Backfire upon acceleration

[HeavyFuel]

Made some progress.

Turns out that some one in the previous life of my carb put in .089 primary jets, replacing the .101 that the 4429s is supposed to have.  It runs alot better now.  Not perfect, but moving in the right direction.

Gonna tweek the timing next by bringing the mechanical advance down to about 20*, then upping my initial to around 14*, and adjusting the vaccuum down to like 10*.

[HeavyFuel]

Last weekend I modified the distributor plates to give about 20* mech advance, and recurved the springs.   I set my initial at 16* and it timed all in around 36* at around 2600 rpm.  (which now that I think about it, I should have done it the other way around, set my total at 36* and let the initial fall wherever...)

I also took the carb apart (again) and checked the operation and flow of the accel pump.   The check valve between the accel pump well and the bowl might have been a little gunked up...seemed like there was some back flow into the bowl when testing the check valve.   It's cleaned up now, and I'm getting good squirt.   The discharge check looked pretty good, but I cleaned it up a little to make sure air wasn't drawing back into the circuit.

Took the car for a drive last night....45* out.

Feels like the car is running better than it ever has.   The stumble backfire is pretty much gone......it still needs some tuning in the carb.

The engine SOUNDS different with the advanced timing....seems smoother when driving, less lumpy on idle.

The choke it still staying on a little bit in this cooler weather because of the blocked crossover.   I'll have to work on that. 

Getting there.