Well, I got the new motor in and running, (350 vortec) now I'm down to fine tuning. I runs great down low, but can't get the ping out of it above half throttle. I'm running 93 octane, with initial @14 where it idles best and no hard start. Do you need to limit or extend the amount of mechanical generally on a stock unit? Trying to avoid shelling out the $ for an adjustable unit if possible. So if I'm at 14 and want say 32 I would need a dist. w/18*, and then use different springs to get it to come in at say 2600-2800? If that's right, is there a way to tell what the dist. has built in it without trying to watch the tach, timing light, and throttle?

watch the tach, timing light, and throttle?

That's how its done on the cheap. use the idle speed screw to set the speed so it stays steady.

there is a pin under the advance plate. it rides in a slot. the bigger dia the pin or shorter the slot the less advance the dist will provide.

experiment away.

The pins mentioned above will do the job, I orginally went down that path, I ended up with problems of loose/ bent pins and often binding and inconsistances...I tryed small shims that dropped over the orginal pins also...these tended not to give a very smooth (and therefore inconsistant curve) movement...even thu it appeared so by hand.
I also found that often the amount needed to reduce was more than the avalible gap in the slot alowed.
The springs only limit the rate of the curve...not the total cenrtfical in the dizzy.
HEI s vary from model to model as to the amount of advance according to what the came off...truck ,car and model of each...there are 100s of vararions from about 16 to 30 plus deg.
To make an adjustable Stock HEI...
At a piont on the main plate just out side the movement of the counter weights base mechanism, drill and tap a hole.
Using a heavy, x head screw that has a larger than normal diameter head, machine the head into a cam lobe shape...as the screw is turned in diff positions it acts as a stop for the counter weight mechanism, changing the total centrical advance available.
With a small spot of 4 diff coloured paints, drop int the end of each of the x ends in the top of the screw...establish the amount of centifical for each position. This makes easy reference pionts when adjusting latter.
Use lock tight or a star washer to stop the screw moving.
If the HEI doesnt have enough advance, carefull machining of the surfaces between advan mechanism and weights will do this.
You have to machine some meat out of the underside of of the rotor to get more advance, and some carefull maching of the surfaces between the counter weights and counter weight mechanism.
Caustion here thu...There are 2 bakerlite 'pads' that the counter weights slide on...these will need replacing with 2 new ones with larger tops to stop the counter weight dropping past the old ones and jamming open.

Changing A pionts dizzy is similar.

Before making any changes, or even attempting to play with dizzies...Make sure the countrer weight bushes, shaft bushes etc are all in top condition otherwise u just end up banging your head against inconsistancies.

Ok, thanks for the tips! I'll give it a try, and if I mess it up I'm not out much anyway. One thing though, does it sound like I need to limit or extend the amount of advance? If it's hard to say which way to go, I guess I'll get a buddy to sit and rev it up while while I watch the light and see exactly what it's getting for total.

So u havnt established actually how much Cent is in there...?
Make sure the springs are not too heavy.
knock intial back to about 10 deg.
With timing light take rpm up till the advance stops, note the #degrees...minus the intail and thats what is in there.
Be warned thu...lets say it stops at 3000 rpm and 35 deg (just radomly chosen numbers ok) then u take it rpm up a further 1000 rpm u may notice another 2 or 3 deg in the curve...This is not part of the curve...it is play in the dizzy shaft, weight bushes, pins bending (loose).

The main shaft bush I could not get over here (NZ) and the shaft was also worn a little/
I turned the shaft down..(lathe) to remove wear and turned a new bush up out of a rod of phos/bronze.
I couldnt get new pin bushes, so made new ones by drilling the right diameter core teflon.
So from a HEI out of a rubbish bin, by the end of the afternoon I had a new one...that was a bout 15 yrs ago...still as good as new.

To establish you curve, run a forum search for some old posts ping curve

Yeah believe me, I do a ton of searches and can usually find answers there. Just couldn't find much about people messing with the stock units, besides springs. I have a couple dist. laying around so I will see if there is any diff. in the length of slots in any of them and go from there.

Another area to watch is where the wires from the module, exit the dizzy at the base...in particular the insulation. The copper wire strands tend not to break and are ok...
The compund for insulation is crap