Well in days gone by, well-prepared shops had distributor machines, with a guy who knew how to use them, and you would bring your distributor to him, with the curve you wanted, and he would make it happen, by tweaking the springs and such, for instance here is the curve I had for my race car (all in at 3000 rpm):
Dunno if shops like that exists nowadays ...
But you could do trial and error on the car using a timing light that showed total advance???
Dave
-- Edited by davelacourse on Wednesday 26th of May 2010 08:09:48 PM
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1956 Pontiac Pathfinder 2dr sedan, 496 - dyno'd 545 hp, stick shift, 4.11 posi - Hot Rod
Back in the 70's I bought the kits with the various weights and springs and did some trial & error adjusting with a timing light. Seemed to work well enough but I am sure it would not produce the results you could get with a distributor machine. I had an uncle (a mechanic) with a late 70's half ton with a 454 and I remember him saying he couldn't believe how much difference it made - again, making changes from the little kit of weights & springs.
I did have a distributor recurved on a 350 that I had built for propane. I had a book that gave the recommended curve and I took it into a shop in Calgary - can't remember the name of the shop, but they had a dyno as well. Can't say I noticed much of a change.
HEIs are the worst of the bunch because of the weight of all moving parts it al depends on the engine and what it likes your trying to speed up how fast the timing comes in go with the supplied weights and medium springs take it for a drive
1956 Pontiac Pathfinder 2dr sedan, 496 - dyno'd 545 hp, stick shift, 4.11 posi - Hot Rod