The centrifugal-advance mechanism within an ignition distributor can seem scary and mysterious to hobbyists. Some believe years of schooling, decades of experience, and professional tuning equipment are the qualifications required to tame the beast. Others reason that as long as their particular engines aren't detonating at high speed, they'd rather forego any potential performance increase available when optimizing the centrifugal advance for a given combination—to avoid angering the mystical distributor spirits that can rain down uncontrollable detonation in a moment's notice.
1. Most Pontiac V-8 engines produced through midyear ’74 were fitted with a points-type ignition system. The distributor contains a cam assembly, which rotates with the main shaft that opens and closes the contact-points set. The assembly also houses the centrifugal flyweights that advance spark timing as engine speed increases.
Ok, so the fables are a bit exaggerated, but there are many hobbyists unwilling to tackle distributor tuning because it seems very complex. The truth is, once you grasp the fundamentals of centrifugal-advance operation, accepting the fact that it's nothing more than a mechanical function and can only do what it's programmed to, you quickly begin to realize that there's no magic to it! And getting your Pontiac's points-type distributor to do exactly what you want can be accomplished with a $10 advance curve kit and the same $2 protractor your child uses in geometry class.
You can do it in your own garage in less than an hour...
You see, a protractor is graduated with degrees of rotation, and the advance mechanism in an ignition distributor operates on the same principle. As distributor speed increases, its flyweights advance the firing position, and it's stated in degrees of rotation. By manually advancing the distributor and referencing it to the graduations on a common protractor, you can accurately predict the amount of centrifugal advance a particular distributor provides, and potentially alter that amount by swapping certain components and/or using the limiting bushing supplied in many aftermarket advance-curve kits. Best of all, you can do it in your own garage in less than an hour, and it only costs a few bucks. Here's how.
19. As we predicted, the limiter bushing supplied in the Moroso kit has limited advance by 3 distributor degrees. Our distributor now provides a total of 20 crankshaft degrees of centrifugal advance, and it does so without the risk of additional advance that could induce engine-damaging detonation at high speed. All that’s left is to install the distributor in the engine, add in the initial advance to get total advance to 32-36 degrees (depending upon your combo), select the springs that provide the desired rate of advance using an adjustable timing light, and you’ve recurved your distributor at home for just $12!
