Another timing curve question

DrCharles said
What do you think about this one for the super-light? McMaster-Carr
Wire .018", ? coils, Coil OD 0.240, Length 0.75", lb/in 0.78
Looks pretty close to the Mopar P2932675...

I have a heavy spring with a loop that I think came from the stock distributor:
Wire .046", 6 coils, Coil OD 0.279", Length 0.985" (measured inside the wire on each end). OK for the heavy one? (of course, I don't know how much retard will come from the Jacobs ignition box).

Seems like worth trying.

DrCharles said
With those springs, do I need to keep the FBO limiter plate which limits on the outside vs. welding up the inside of the slots? Or just leave the unrestricted (stock Mopar) advance range (around 26-28 degrees I think) as long as the engine will start ok with 6-8 BTDC?

You may have a better idea when you open it up. With a small pry bar push weights out until you see the heavy spring take up some slack. Is right at the begining, at the near the limit or something in between?

Not sure whether your engine will love being started at 6 or 8 degrees. Might be fine. A lot of the smogged engines had initial timing like that. On the other hand, yours is a a bit more radical than even the most radical factory engine. We can make some guesses on graph paper too.

DrCharles said
Could you explain in more detail? No 4-corner idle.

As best I can tell, transfer slot exposure on the secondary side is typically none or minimal. Secondary pump shot covers any delay in supply from the secondary t-slot. I don't know the exact timing of when secondary t-slot comes into play - I assume it is mostly for very high speed cruise or lugging a load when the secondaries a only somewhat open.

Each carb is different and each need is different, but generally the secondary t-slots are shorter and higher up in the throttle plate than on the primary side. So to get the secondary t-slot square requires the secondary throttle plate to be more open than the primary side. This is possibly comtributing to why your idle speed is so high and the engine likes over 22* inititial timing.