Distributor And Dwell Puzzle

Ok, only had the jeep since last summer. F head engine. Started chugging at a lower speed than it used to and misfires a lot at idle so I started by cleaning the (Solex) carb with no change. Checked dwell/timing. Timing is 5 degrees at idle, advances an additional 10 degrees at 2400 RPM and dwell is all over the place so I changed points,cap, and rotor. Dwell still reads all over the place, adjusted the timing with minimal misfiring at idle. Test drive all the way to 54 mph with no stumbles and idle ran smooth. Go to drive it tonight and it will barely stay running. Checked timing again and it’s on 5 degrees and running terrible and stumbling all over the RPM range. Do I need to replace the distributor or is there something I missed?

 

Condenser was also replaced. Wires, coil, and plugs are new as of the end of last summer.

 

ditto on the condenser,seen a bunch bad right out of the box.

 

The bushings and/or advance springs in the distributor may be worn.

Test 1
Remove the cap
Grasp the rotor
rotate it clockwise as far as it will go (won't be far)
release
Bouncing back means the springs are good
Not springing back could be stretched springs and/or worn spring posts.

Test 2
Now remove the rotor
Grasp the top of the shaft
try to move it 12 to 6 and 3 to 9
if it does move appreciably, the bushings need replacing

 

Thanks, I’ll swap the condenser and run theses test. I’ll let you know what I find out.

 

Scoutpilot speaks the truth, Grasshopper.

Dwell will be very inconsistent if the distributor bushings and shaft have play in them, since the point gap will change and that controls dwell time.

Try shaking the distributor shaft from side to side, if it is loose it needs to be replaced

 

Well first thing I found is that new rotor had a ton of play in it so I swapped to old rotor. No significant change. Twisting the rotor counterclockwise it moves and returns to original location. Clockwise does not move hardly at all but does not return. When wiggling the shaft, there is a slight amount of play in each direction. Should there be zero movement or am I looking for “loose”?

 

It should not be loose.

Define "slight." Perceptible motion is at least .002" minimum.

On the other hand we have only your description of "all over the place" for dwell duration. Some flutter on the dwell meter may be acceptable, until it starts affecting the timing significantly.

You describe timing as "five degrees." Can we assume that means BTDC? And is it steady, or wandering?

It is possible your perceived performance issue may be somewhere else entirely. (cough*solex*cough)

Have you tried a vacuum gauge on the intake manifold?

 

Yes it is 5BTC and mostly steady except for a rhythmic skip. I describe the shaft as slight as in perceptible but not loose or wobbly. The dwell is on a digital timing light and it is my first time using it so I’d like to rule that (the meter) out as the issue. I ordered an analog one so I can see what it does in real time rather than a digital refresh. It currently registers between 15 and 50. Does not matter how a adjust the gap. I understand it can be carb related, but when I first changed the points there was a dramatically positive result. The dwell is what I have as suspect right now so I’m trying to rule that out first. Someone on this forum once told me 90% of fuel problems are electrical.

 

I also do not have a vacuum gauge yet. Can you recommend a decent one that won’t break the bank?

 

AFAIK they are all simple and inexpensive.

 

x2.

 

Clip was still in rotor, it was able to turn probably 10 degrees (5 each way) without the shaft moving points spring felt much better than the original point. Parts all came from Walcks so I assume they were good quality.

 

Thanks I’ll look into this.

 

Old or fresh gas?