[Schurkey]

Throw the heaviest springs you can find into that distributor advance; if you can be sure that the weights aren't moving around at idle, and the timing mark still jumps--you know not to bash your head trying to "fix" the centrifugal advance.

While you have the distributor cap off, and the timing pointer nearly lined up--turn the crank backward with a long breaker bar and socket until the rotor moves, then turn the crank forward until the rotor moves. How many degrees of crank rotation do you have with the rotor not moving? I'd allow ~10 degrees of crank movement for a grandma-car; much less for anything with performance aspirations. Excess slop is either the timing chain (very likely) or the end play in the distributor shaft (not likely if you're turning the crank slowly) although gear lash between cam and distributor could theoretically be an issue, with iron gears it really isn't something that causes much trouble.

If your timing pointer is accurate, start looking for electrical issues that would cause the starter to not have full power. Maybe your starter is going bad; or the cables are corroded or undersize. You shouldn't have any problem cranking that engine with 10--15 degrees of initial advance. More than 15 degrees may--or may not--be an issue depending on the rest of the engine combo such as compression ratio and valve timing, etc.

 

[Schurkey]

thanks guys, just hung up the phone with Jegs, I have an HEI advance kit and an adjustable vac. advance can on the way as well.

That's too bad. Every commercially-available advance kit I've seen is TOTAL JUNK. The weights are much too light; full advance takes too much RPM. There have been complaints about low-quality springs that wear out quickly, too. Since the Crane vacuum advance unit comes with (or at least USED TO come with) a centrifugal spring assortment, that and perhaps some junkyard HEI weights and center plates would be all you need.

Would it be foolish to "lock out" the cent. advance all together with a couple pieces of wire to see if my timing is indeed jumping, or am I asking for trouble? Seems to me it would be sensible to eliminate that variable.

If you can do that without screwing up the rotor mounting--fine. The entire point of the heavy springs was to hold the weights in (for testing) so that you could eliminate them as a source of your timing fluctuation.

My electrical *should* be fine, new starter, seems to wing over nicely, good clean connnections, engine is grounded well, directly to the battery, then 2 ground straps to the body from the block. I am running an Si style alt. with the ext. regulator removed, and all seems well. If I get the timing all sorted out and it still starts hard, then obviously I need to chase electrical issues as well. Parts will be here Thursday, I'll check what I can this evening! Thanks again, Justin

The engine shouldn't be hard to crank at under 10 degrees of advance. Yup, you need to verify the accuracy of your timing pointer/damper mark. IF that's good...clearly, something else is wrong.

You need to know for sure whether the centrifugal is bouncing or not at idle rpm.
I would definately tie the weights off or remove them temporarily and see if things settle down. If it's not coming in early, you probably don't want to be changing the springs for heavier ones. Their either a problem or their not.

Yeah, I intended that the heavy-ass springs be used for testing; in normal use you only want springs stiff enough to keep the weights in at idle. But if the weights are NOT in at idle--then somewhat stiffer springs are in order.

You need to get another timing light and make sure yours reads the same. Check a dialback with a non dialback and vise versa.
Squido

Good point. Dial-back lights can create some problems--and doubly so with MSD-style ignitions.