Wandering timing

1950 - 1952, M38, questions, discussions, regarding anything related to the M38.
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Scott in NM
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Wandering timing

Post by Scott in NM » Thu Aug 05, 2021 2:53 pm

Put a timing light on my stock M38 today and the timing wandered from about 7 degrees BTDC to TDC and back over the course of about 2 seconds at idle. Prior to this, distributor had been disassembled, mechanical advance cleaned and springs checked, shaft bearings replaced, and points and other parts set and ensured tight.

1. Ran timing with #4 to check distributor cam wear and performance was exactly what #1 did.
2. Distributor is in the fully retarded position to get the timing correct.
3. Mechanical advance seems to work as the degree of retard progresses with increased rpm but still wanders the same spread as at idle.

Did I miss something? Something else I ought to check to eliminate this wandering?

Scott


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dpcd67
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Re: Wandering timing

Post by dpcd67 » Fri Aug 06, 2021 2:11 pm

Two things; if your dist has to be set at either end of it's travel in order to be timed then the oil pump needs to be removed and indexed correctly.
And if it wanders over several degrees, then either the oil pump gear or the cam gear is worn. Can you rotate the dist shaft when you turn the rotor? Or the slot in the oil pump is worn, or the distributor shaft end is worn. Sometimes worn bushings will cause that too but not as bad.
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GPW1263
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Re: Wandering timing

Post by GPW1263 » Fri Aug 06, 2021 7:04 pm

Before getting completely crazy, let's check that rotor first. Is it cracked, or does it have a sloppy fit on the shaft?

(ask me how I know)


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