Timing Jitter and End Play
A. The end play on a stock
points advance setup is .5mm. The end play for a MikesXS
advance rod is 1mm. The stock end play is OK and should not
produce a noticeable timing jitter. The end play on Mikes
advance rod might show some jitter if you look closely. You
could install a .5mm washer type shim in the MikesXS setup,
but I would not advise shimming the stock rod as some end
play is needed for thermal expansion of the rod.
B. If you are going to install a .5mm shim in a MikesXS rod, then install it on the advance side.
C. In both cases, the amount of timing jitter will not affect the operation of the engine.
D. Ensure that the PAMCO rotor is fully seated on the end of the advance rod. The best way to check for this is to remove the rod and do a test fit. Do the same for the advance slotted disk.
Checks and Adjustments
1. You should also adjust your timing chain tension. A loose timing chain will cause timing jitter, as will a worn out timing chain.
2. Check the tension on the return springs. The advance should return so the advance weight arms are up against the slotted disk.
Notice that you can see some tension in the springs (spaces between coils)
3. You must have either resistor caps or resistor plugs for proper operation of the timing light.
4. The idle must be steady.
5. Engine must be warmed up.
6. Excessive idle speed (>1200 RPM) will cause the advance weights to be right at the point where they start to advance, causing timing "jitter".
7. Here is a video of the correct "snap back" action of the advance.
1. Could be a timing light
issue. Try a different timing light.
2. One of the plug wires is not making contact in the coil tower or the plug cap. Measure the resistance from one cap to the other to ensure you have continuity through the coil.
3. Low battery voltage to the timing light. Charge battery
4. Loose alternator rotor. Tighten the rotor nut.
5. Loose spanner nut holding the advance plate to the cam. Tighten.
6. Weak magnet in the PAMCO rotor. Aim the timing light at the rotor and see if it is standing still or is it jumping back and forth.
You must have this crisp snap back action for proper timing.