Big lumpy cams in a carbureted deal get locked.

You put the MSD distributor in it with the big bushing and light springs. And still have to make it idle at 1000 for it to stay running. Try to slow it down and the timing backs down, slowing it down even more until it won't run. Or it stalls when you drop it in gear. So you wind the idle up to keep it spinning fast enough to keep some timing in it so it will stay running.

Make a bushing or whatever, to get enough timing in it to idle and it ends up at 25, at least. Well I'm only running 34 and it's all in at 1500. Nothing happens below 3000 in my world, so why bother.

I've done the light springs, make a big bushing, drill the throttle blades, fiddle around with it, and every time I put a few more degrees of base timing in it, it likes it. So...Lock it, set it at 34 or whatever. It will idle at 800 in gear. Response will be sharp and crisp and it sounds happy. Every time.

And I've gone back and tried it the other way because "it's not supposed to be locked and it should have a curve". And the engine tells me "gimme timing".

Anything of mine, or anyone else's who spends the money and lets me, gets a crank trigger and a distributor that just spins the rotor around the cap. Easy, effective, simple.