I have a '46 Chevy Pickup with a '53 235 straight six and when I am out cruising and there is NO load on the engine I get a chattering noise from the engine. I run a 10w 50 oil and I always add a lead substitute when I get gas.
I would appreciate any tips.

A side note can you use a timing light on a 6 volt battery?
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1946 1/2 ton Chevy Pickup
1954 235 cu in
3 speed on the floor