Ignition - Advance Basics

For those on a budget with only a more generic light, the easiest way to read total timing is to attach a timing tape to the harmonic balancer. MSD makes a series of inexpensive timing tapes on a sheet with different tapes for specific balancer diameters. These tapes adhere to the balancer and produce easy-to-read figures. It doesn't really matter which timing light you choose to use, as long as you always use the same light to set the timing on your engine. Mistakes occur when you use a different light each time. We've seen lights vary by as much as three degrees on the exact same engine at the exact same rpm.

Checking The CurveMany car crafters think they have to put their distributor on a machine to determine the timing curve. While this does work, it's also possible to create a timing curve with the distributor still in the engine. To do this, you'll need a timing light, timing tape, a tachometer, a paper and pencil, and a buddy just to make things easier. Here's the drill.

First, unhook the vacuum advance and measure initial timing. Let's say it's 10 degrees at 900 rpm. Next, rev the engine to 1,500 rpm and measure the timing again. Now let's say it's 14 degrees. Record the timing in 500-rpm increments until the advance numbers no longer increase. Let's say the curve looks like this:

Now let's reconnect the vacuum advance and redo our test and the results look like this:

Now let's say you really want to have 36 degrees of total timing without the vacuum advance, so you add 4 degrees of initial timing. For fun, let's say that this makes your WOT timing curve perfect, but now the engine surges at part-throttle because you have 48 degrees of total timing with the vacuum advance. The best bet would be to braze or epoxy the slot closed slightly in the vacuum-advance canister (you should remove the canister from the distributor to do this).

By balancing initial, mechanical, and/or vacuum advance, you can create your own custom advance curve tailored specifically to your engine and drivetrain combination. The best part of all this is that you don't have to spend a bunch of money to do it. All it takes is a little time and effort.

Quick TechNeed to do a quick check on the ignition curve on a buddy's engine, but you don't have a timing tape or a dial-back timing light? We'll show you how to make a homemade timing tape, look like a tune-up pro, and amaze your friends all at the same time. All you need is to measure the harmonic balancer diameter, determine the circumference (3.1417 x diameter), and then divide that dimension by 180. This will give you the distance equal to 20 degrees. We've listed the dimensions for four popular balancer diameters so you don't have to do the math: