Vacuum Advance and why to use it on the street

[Plowman]

I didn't want to post things on a for sale thread, and got some help from my son just to get the ball rolling. I appologize for giving a negative spin on the NOS vac advance.

Surprisingly, there were several on that thread who did not seem to understand the relationship the VA has on an engine with today's pump gas.

There is actually a fellow who writes a decent explnation at this link:
http://www.kitcarmag.com/techarticle...on_timing.html


Quoted from that link "Any original or high-performance aftermarket replacement distributor must have the ignition spark advance curve(s) tuned for your engine and the gasoline you will be using. Most of the high-performance replacement ignition systems, such as an MSD distributor, come with a very conservative ignition advance curve installed in the distributor. A new MSD distributor comes with a selection of advance springs and bushings so you can set the advance curve you want. However, most vacuum-advance-equipped distributors have too much advance for the reformulated gasoline of today."

Locked out distributors and too much VA at idle contribute to overheating (glowing red) pistons rings and premature blow-by. Yes you can drive it, but is not ideal.

Hopefully we get some good posts and comments here, and with some patience I'll try to share my understanding and techniques to get ideal street tunes on todays fuels. We could all learns from a decent thread- myself included.