I just put a Crane adjustable advance on my MSD ready to run distributor. It came with a limiter plate that has notches every 2 degs. I want to limit the vac advance to 10 degs so I installed the plate with the fifth notch against the cannister arm. Now, how do I adjust the rate? If the hex screw in the nipple is turned fully clockwise does this give full rate? How many turns can you go counter clockwise? I have it hooked to manifold vacuum.

I would aim for having all 10° "in" with about 2" less vacuum than you have at idle. For example, If your idle vacuum is 10", aim for having it all in at 8". If you have a mighty vac and you know what vacuum your car pulls at idle, you can set it on the bench.

You want the vacuum advance all "in" while idling or the timing will bounce around with the vacuum causing the RPM to vary, causing the vacuum to vary, causing the RPM to vary, etc. :eek:

-Mark.

What Mark said.....plus
get a long hose for your vac gauge and check your idle vac with the trans in gear.

You may not be able to achieve both ends of the curve with the way Crane vac stops work. The eccentric notched wheel limits the low end of the curve. Dave Ray has a limiter kit that puts the stop on the top end and you use the adjustable spring to do the low end.

Put the limiter plate back in the stock position and follow Cranes directions. You can try to start somewhere in the middle and you may end up without any pinging but you'll never know if you could have run just a bit more advance. It's a longer process but you'll get the most from the product by doing it their way.

Crane says to go clockwise as far as it will go to start and drive and listen for part throttle ping. If it does ping adjust 2 turns counter-clockwise and test drive again. If you end up going 10 turns or more counter-clockwise you then want to go one knotch on the limiter plate and go all the way back clockwise and start testing over.

Each notch on the limiter will pull 2degs out of the vacuum advance. Caution though as it adds the 2 degs to the mechanical. That means if you were reading 14degs initial (vac plugged off) and 34 total one notch on the limiter plate will bump that to 16 initial and 36 total. Just be aware and re-adjust your timing after making a change to the limiter plate.

You've pointed out the shortcomings of the Crane system very well. By putting the adjustable stop on the lower end of the assembly and limiting the return of the rod to its normal resting place you create two conditions:
1. You change the initial advance and the total advance whenever you turn the stop.
2. You change the amount of tension on the spring in the VA can, which changes the amount of vacuum needed to activate the can.

If you install a stop on the outer edge of the actuating rod you alleviate both of these conditions. Moving the stop does not alter the mechanical timing and it does not alter the amount of vacuum needed to start the curve.

Here's a catalog listing of a such a stop:

http://www.kendrick-auto.com/ignition.htm