Manifold Vacuum Experiment

'How much idling do I f**kin' do?' Like every body else, as little as possible. But driving circumstances dictate that idling is & will be necessary at times.

Here is a another statement from Jos51700 that is 100000% wrong.
'If you want spark advance during wot, you're an idiot'. Post #64.
The only idiot is the person who wrote this & obviously doesn't understand ign.

You DO want spark adv during WOT. Here's why. You could go to WOT from idle, from, say, cruising at 2000 rpm....or anywhere in the rpm that the engine is capable of.

The mixture takes time to complete the burn process & exert maximum force on the pistons.
It has been determined that 14-20* after TDC provides the best mechanical advantage for max force to be applied to the pistons. It is not TDC like many think.
At 5000 rpm, there is only half as much time for the burn to complete compared to 2500 rpm.
That means as rpm increases, the ign advance needs to start earlier [ more crank degrees BTDC ] so that the burn is completed for optimum mech advantage.
Another way to look at it: say dyno testing showed max HP was made with 36* of advance.
At 5000 rpm, it takes half the time for the crank to rotate 36* than it does at 2500. So that is the centri curve starts with low advance & increases with rpm...so the mixture has the time to burn.

The vac adv drops to zero or close to zero at WOT. If you had the factory 12* BTDC as initial timing......& no advance curve....you would have 12* still at 5000 rpm....& be way down on power.