Vacuum Advance and why to use it on the street

[Keith Tedford]

When we bought our L78 car in '98, we could still get Ultra 94 and similar. Now, all I seem to find is 91 and the engine would ping. I could back off the timing until the engine stopped pinging but then there wasn't enough timing on the bottom end which can lead to over heating. That's where shortening up the advance curve came into play. You have to figure out where your engine works best on the bottom end. Then figure out where it works best in the upper end rpm for advance. Then tailor the distributor to suit. In my own clumsy dumb ass way I have managed to get close to 200K miles out of the 427 and have run the L78 on unleaded for about 37K miles with zero problems. Running a little rich on the jetting also seems to help with the pinging. If I can have my cars running fine, it can't be all that difficult, yet I'm always reading stories of red hot headers, melted pistons, over heating and engines detonated to death. There are vacuum canisters out there with different amounts of advance. Pick a suitable one. If not get an adjustable unit.