1931 Chrysler Jerking in all Gears

[JeffGreen]

I’ve acquired a 1931 Chrysler that’s in museum condition. While driving in all gears, I am getting a jerking. At idle I have great acceleration and can hold steady RPMs. The carburetter was rebuilt recently plus the transmission was also overhauled three years ago by the previous owner. Does anybody have an idea what could be causing the problem?

[Matt Harwood]

Possibly too much timing advance? That can often cause a surging or jerking at low speeds and under acceleration. Make sure the timing is set to factory spec.

[EThomas]

I suggested looking at the brakes, in your post in the General Discussion section.

[JeffGreen]

While in neutral you can accelerate hard and slowly but when in each gear when you accurate it's like it starving for fuel but that's not the issue.  

[Gunsmoke]

So many variables, sounds like a power problem, compression, timing, plug wires, a cylinder misfiring, ...... plugs, fuel mixture.....and a dozen other possibilities. My friend 80 YR OLD Larry would have it narrowed down in 5 minutes (classic fuel, electric, air, compression quartet) (may also be a clutch issue) but he is not available on Saturdays! The fact it idles smoothly and can be revved smoothly suggests it is a power issue to me, but I'm not Larry..

[Grimy]

Hard to diagnose without experiencing the "jerking," but my first inclination would be to temporarily replace the coil with a known good one, and the second would be to add a condenser to the coil primary, and ground the added condenser's case with my trusty 10-gauge wire with alligator clips, without disturbing the installed condenser.  On the ignition side of possibility, the failure occurring *under load* suggests coil or condenser.  What is the resistance (ohms) between the two primary posts on the coil?  Should be about 1.5 ohms.

[Oldtech]

As others have said prime suspect is ignition. A weak spark will run under light load but fail when cylinder pressures are up (foot on the loud pedal). Grimy has good advice, also check that advance mechanism is free and working properly. 

[EThomas]

To add to this, check your generator as well. I had to get mine rebuilt as the bearings were locking up as it got warm. 

[Farmallregular]

In addition to previous suggestions, check the spark plug wires for cracks in the insulation, or just replace them.  Vehicles of that era had copper spark plug wires, and if someone has replaced them with modern resistor wires it can cause misfires.   A good auto parts store can get copper spark plug wire in bulk and the terminals for both ends.

 

Keith

[paulrhd29nz]

Have you checked your fuel tank? Could be full of museum crud. Also have you changed the float height for our modern crap fuel ??