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Timing jumps around at idle


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Like the title suggests, the timing on my 521 jumps around 4-5 degrees at idle. I'll set one end of the jump to 10 degrees and it'll bounce back and forth from there to 15 degrees and in between.


The engine is an all stock l16. Dual points distributor. I had thought this might be the timing chain because it was rattling a little. I replaced the timing set this weekend and it still does this. Realistically, I thought the distributor was the most likely cause, but since I needed to replace the chain anyway I was hoping that would take care of it.


Do you all think this is probably the distributor? Is this just kind of the nature of points or do I need to look for something loose or broken in the distributor? I plan on going to a matchbox distributor eventually, but for now I just want it to be servicable.

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Unlike most engines, the distributor on a L-engine is driven by the crankshaft. Most likely culprit, is the distributor bushings are worn. If you can find a matchbox distributor, off a later L-20 engine, you can get rid of the points, and have a better ignition system.

If you get a matchbox distributor, get its pedestal also. Try to get the matchbox coil too.


You might try to take the points distributor apart, and cleaning the advance mechanism under the plate the points are held on. Look for a broken spring, or a spring disconnected. If the idle speed is too high, that could cause the timing to start advancing, also.

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Normally there is NO vacuum advance at idle, but if the idle is set a little high some ported vacuum advance may be gettin in.Take the vacuum advance off and see if the jumping is gone. If not, Daniel's suggestion is on the nose.

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