Re: Weird Surging

Posted by Redhexagon On 2024/2/23 0:52:24

The carburetor is definitely not lean. Rich, actually. I live at high altitude and left the standard jets in it because it's not rich enough to hurt anything and it allows me to drive to lower altitude without damaging the engine from being lean.

It's not the gas cap. I've driven with the cap off with no change.

It's not the vacuum advance. The old vacuum advance didn't work and it still surged the same as it does with the new vacuum advance.

It's not the points or condenser. I've been through several sets. No change.

It's not the fuel pump. Three different fuel pumps all acted the same.

Nothing is out of place or clogged in the air cleaner. I soaked that whole thing out with kerosene and thoroughly inspected it before I ever drove it.

No valve springs are broken. I looked at them all when I had the valve covers off not long ago.

The fuel line is not clogged. I can blow a high volume of air back through it. Pinhole air leak, maybe, but usually that makes the pump lose prime when the car sits and I do not have that problem.

Motor mounts are good.

Throttle linkage is good.

Exhaust is not clogged.

Carburetor bowl vent is sealing properly and adjusted properly.




I wonder if it's some sort of fluttering in the air cleaner or carburetor. I can imagine the oil in the air cleaner getting sucked up into the gauze then draining back and getting sucked back up again in a fluttering rhythm. Something similar could happen with the air and fuel flow in the carburetor as well. Some models of four barrel carburetor can get secondary flutter. I might switch a pleated paper air cleaner onto it or disable the secondary barrels of the carburetor and see what happens.


It is definitely a weird one.