73 360 Ignition timing after Chain replacement

Bewy said

You have an engine that is nearly 50 yrs old. Quite possible & likely cam has been replaced & the new one has more oomph. Which would explain the need for more timing at idle for best idle quality. If you did inadvertently install the cam 4* advanced or retarded, doesn't mean it is wrong for that engine. Could be, but only way to know for sure would be to put the engine on a dyno & test all three cam positions.

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Yeah, the RV it was in had only 48K miles on it, and hadn't been registered for the road since 2001. I really, really think the engine had never been out......but I guess the cam could have been replaced at some point, and that could have been done without removing the engine.....there were signs the water pump had been replaced but every other bolt seemed original with factory paint on it still......The cam could have been swapped for an RV Cam, by the company that did the RV conversion (Beaver coaches, Bend, Oregon) in 1974. You would think they would have marked new tune up info somewhere though.