Erratic idling, wear in distributor?

R

restojon

New Member
I recently had a look over the ignition system and fuel system on the SC and whilst checking the timing with the strobe found the timing was out by about 4deg. so I adjusted the distributor accordingly and it was this point the can of worms well and truly opened. I could not get the car to idle at the correct speed or anything less than 1000rpm (suffered extreme vibration), whilst adjusting the tickover I was using the throttle at the carb end to keep it going and realised every time I revved the car the rev's settled at a different rate every time. Every time I took the revs down to approx 700rpm the engine was shaking very badly and threatening to stop altogether. after a little fiddle with the mixture got it to run at 750rpm, revved it then it wouldn't idle then after no adjustment and another rev it was sitting at 1000rpm again. checked the timing with the strobe and it was still on the money when running at 700-750rpm but running erratically. I've adjusted the choke correctly and I've checked all the obvious things and changed leads plugs and I have a pertronix so no points or condenser to change and everything that end seems fine. I had the distributor apart to check the advance weights were moving freely and realised that there is some play in the shaft that runs through the distributor, I'm presuming this is not normal on an SC? I know a worn drive could cause erratic running as the slack in the drive varies each time the revs increase and decrease but surely that would show up on the strobe? Would anybody be able to share their experience here and prevent the inevitable John Cleese branch sketch happening on my driveway?
Thanks all.
 
I had the exact same problem on my 2000tc last year after switching to a petronix system. In my case it was weak return springs for the bob weights. You'd rev the engine and the idle would settle at a much higher speed with the ignition staying advanced. Stiffle the flow into the carbs sp revs drop and it would return to the original timing. In my case I confirmed it by having the wore for the petronix module was close to the cam. I could cause drag on the cam by pulling on the wire and thereby causing enough drag to reset the bob weights.

I used a guy in Minnasotta to rebuild my dizzy and recurve to spec with modern fuels and engine setup in mind. I think he was very reasonable ($125?) and it was worth every penny. His company is called advanced distributors. There's also a very helpful chap in the uk google the distributor Doctor.

Cheers,

steven
 
Just a quick follow up on this problem for anyone who's interested. I've had this running problem on and off for a while now and after a batch of duff fuel recently have had to have everything apart for a clean up and whilst resetting everything I had the dizzy apart to have a look around that too, what I found was that the base plate and pick up coil had worn and the pick up coil had moved away from the rotor part of the Pertronix unit creating too much of an air gap. I've had a fiddle and reset the gap and it's behaving itself a lot better now. One worth watching out for for other Pertronix users, one of those basic things that can be easily missed.
Thanks for all your helpful posts. :D
 
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