So one fine day, a few years back, I had one of those 'Eureka' moments.
(We have those a lot here in California - "Eureka!" is our state motto.)
I realized the spark scatter I was seeing when setting my timing coincided perfectly with a sorta soft spot in the transition between idle and full-on throttle.
Soft spots like that are all 'sorta'. We don't really want to admit they exist.
We blame them on temporary things - dirt in the jets, bad gas, too much time since the last tune, sun spots, etc. etc. Deny, deny, deny.
Anyway, way back then, I decided to man up and do something about the sorta soft spot. I put two Kelloggs box tops and 50 cents in coin in the mail, and two weeks later, a Magnaspark II showed up in my mailbox.
Like many folks had been saying, that did the trick. My timing mark was now suddenly visible across the whole rev range and the engine was smoother between idle and the fat part of the torque curve.
Well, sorta. There may have still been just a tiny hesitation there. Or maybe it was just bad gas.
Anyway, ever since then, I've been thinking about those little sets of advance springs they ship with the Magnaspark. They install the medium (light silver) set by default and since everyone's in a big hurry to hook up their new toy when they open the box, no one messes around with any of the other springs right off, right?
We put them back in the box and mostly forget about them.
Well, I got to thinking if the softer springs bring on more spark advance sooner and the 'fat part' of the torque curve happens at full advance, maybe a little more advance down low could be a good thing.
And damned if it wasn't. On my engine, at least - a two-liter with Weber 40's.
I tried mixing one of the 'blue' springs with the 'light silver' ones (they don't have to match) and, well, Eureka ! It made quite a difference. The transition is a lot smoother and it pulls stronger off idle. (Remember, softer springs make the advance curve steeper, but leave the max advance where it was set before the swap.)
With folks so hung up on what's wrong with their carbs, it's really hard to overemphasize how important solid spark and the right advance curve are to an engine that has no computers to look after its well being.
It's dopey simple to pop in different springs if you want to experiment. They're easy to get to, and it takes maybe 10 minutes. Just remember to check max advance after the change, just in case.
Some day, someone will invent a system that lets you fine tune the whole advance curve just by plugging in a laptop computer to some magic black box - without any springs at all.
That's gonna be great.