Acting like one cylinder firing lean.
AJ I agree with you that a well tuned vacuum advance can be benifical, if you have vacuum at idle. Lumpy cams produce little or no vacuum at idle. I have had several hi performance engines that I ran no VA because the engine had little or no vacuum.
I agree with you, hence the qualifier "most"
But you are missing 90% of the story. By 1850rpm the vacuum in the manifold is building pretty strong and by 2200 it has more or less peaked, and holding pretty steady. If you are running 3.55s or better, your Vcan will work exactly as it should, but even better cuz without it your AFR is gonna have to be rich to prevent tip-in hesitations. Sure you can futz with the pump and make it work that way, but it will never run like it would with proper VA assisted timing. When you feel that badboy start pulling on the can and everything smooths right out and the pipes start to sing, and you are just sipping gas, that is the pay off. We are long past lumpy idle.
I ran a 22*VA even with my 292/108 cam at 11.3 Scr, and reaped the benefits. If you run more than that with an SBM, firstly I can't speak to it, but secondly, a 292/108 is a terrible SBM street cam,lol...... IMO
Here's what else you can do, and I have done, and continue to do;
My power timing is delayed to not be all-in until 3200/3400. I have 28* at 2800. I augment the timing with 22* in the can so am cruising at 50* at 2800. So I always have plenty of timing for part-throttle work. With a small 230 cam, and 180psi cylinder pressure, I have a ton of torque available. When I stand on it, the tires light up anyway below 50 mph so I don't care about a few missing degrees from 2800 to 3400.
So what's the big deal, you ask? The big deal is I burn 87E10 100% of the time, saving about 12cents a mile in fuel costs, and have done so since 1999, over 100,000 miles. And the engine still goes 93mph in the 1/8th, at 3467 pounds. Is $12,000 saved a big deal? I think so.
