Gents: just put a new long block 225 in my 73 swinger and it starts and runs beautifully, but when I put a timing light on it just to be sure, the timing mark slowly but steadily precesses counter clockwise as if the pulley were turning at an apparent 5 rpm.
Distributor is solid, car starts and runs easily and the problem persisted despite using a different non-adjustable timing light, an old bakelight raygu Sun...only thing I can imagine is that the crank key jumped out as I was pressing on the harmonic balancer and the interference fit allows it to rotate...I'll check that of course, but before I do, any other ideas as to what the heck? Anybody else ever see this?
Thanks much
John Foyston,
Portland OR

I've had one do this recently where the springs were too light during a recurve, but in your case you're using a std distributor. If the vacuum advance is hooked up did you use the correct port on the carb? Check the keyway, then disconnect the vaccuum source from the dist. while it's running and see if it goes away (running mechanical, and maybe your vacuum advance pod has a slight leak too.).

anyone else?

-D.Idiot

I saw some strange things in a 302 Ford - it turned out that the clip holding the vacuum advance arm had come off, allowing the plate to dance about quite freely.

It could be the damper is moving. It is not uncommon for the rubber in the balencer to shear. Take a marker and make a mark on the inner hub of the balencer, and continue the mark right to the outer ring. Start the engine and see if the marks stay aligned. If not the rubber is sheared.

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225