All,

On my 1970 Duster with a 340, I have had some issues with hard starting over the past two years. Last year it was cured by installing a new cap and rotor and a new set of plugs. It seemed to deteriorate again - and the plugs look fine. Engine runs great once it starts, clean and smooth.

So today, I pull off my 8 month old distributor cap with about 1k miles on it and find this:


It looks pretty messed up to me. What's causing this? Do I have a rotor phasing problem? The distributor is a stock mopar unit curved to run 22 up front and 35 total. Cap and rotor is Accel, and I am running the FBO aluminum white box and coil. Coil gets full battery voltage. Plugs are autolite 3924.

I'm just curious as to what's causing this. This problem may hasten my EFI/coil near plug conversion depending on the root cause.

Thanks for any help.

the burn marks appear to be very near dead on centered as far as phasing goes. NAPA does offer a rotor (Echlin MO3000) which has a .060" longer blade which reduces the radial gap & helps with circumferential phasing (if needed) as it is the total distance (radial+circumferential) between rotor tip end/cap terminal that if greater (required voltage) than what the (available voltage) can jump will cause a misfire & maybe hard starting (not sure on that but likely). Ideally you want the radial gap to be .015" or a hair more. You could make a mark on the dist metal top rim below the CL of the dist cap bulge where the rotor is at (at rest) & see how dead on the rotor is centered on your scribe mark & only the can changes rotor phasing and an 8 deg can will shift the rotor 8 deg CCW (on a SB) from the at rest position. I think I would check other basics for the hard starting & I would check the reluctor gap

Could your plug gap be too big causing arcing in the cap?

Interesting theory on the rotor. I never knew there was a longer one.

The other thing is the hard starting is only when cold - if the engine is warm it will light right off.

The plug gap is 0.035 just like stock. I never opened them up.

Either improper materials choice or too many joules.

Those Accel caps are a poor choice.

I found what is probably one of those longer rotors in my pile of used ignition parts that looked decent, and a non-worn out cap - put those on to try and the car lit right up on the first crank. Looks like you guys were right.

Thanks again!

You might pop the old rotor back in for a quick 2 minute test just to see if it is the rotor or the cap (or a combo) but what SC said, more likely the cap.

If the car has a carter don't blame the ignition My 340 with a Holley will start any time down to 0 with couple jabs of throttle and no choke. The Carter AVS is a good carb except when high speed handling, start with no choke etc

I used a AVS I have 5 for over 30 years but switched to Holley in the late 90s and never went back