The first step in adjusting engine timing is to disconnect the vacuum-advance unit. To do this, plug the vacuum hose with something suitable like a medium-sized screw.
Next, loosen the distributor with a 9/16 wrench. If the bolt is hard to reach, this special distributor wrench offered from many tool outlets works well. Be sure to keep some tension on the bolt so that the distributor housing will not easily move after the timing has been set.
Most timing lights have three leads: an inductive pickup, a 12-volt connector, and a ground.
To hook up the timing light, connect the inductive pickup to the Number One spark-plug wire and the other two leads to the positive (12-volt source) and negative (ground) battery terminals. To find the Number One plug wire on a Chevrolet V-8, locate the Number One cylinder (driver side, front cylinder) and follow the plug wire to the distributor cap.
With the engine at operating temperature and running, aim the timing light at the timing tab and balancer.
Turning the distributor counterclockwise advances the timing; clockwise retards it. We set this engine at 10 degrees before top dead center (BTDC). After the timing is set, the distributor housing hold-down bolt can be retightened.
You can check your total advance with the distributor still in the engine by using some simple math and a felt-tip pen. See Degree Your Balancer sidebar.
With the engine running at 3,000 rpm and the added marks to the balancer, the engines total advance can be measured and changed with the appropriate springs, weights, and bushings. Hand-held instruments like this diagnostic tester (right) can be used to show engine rpm while monitoring total ignition timing.
To modify total ignition timing, remove the distributor cap and rotor to access the advance springs and weights.
These springs and weights (shown on this stock distributor) affect total advance. By replacing them with lighter springs and different weights (available from several performance manufacturers such as ACCEL), the total advance can be changed to improve performance.
If you have to remove the distributor, position the rotor to the front or No. 1 terminal, mark the housing position to keep initial timing in range after reinstallation, and unhook the holddown clamp and all wires. The distributor lifts straight out.
A handy remote starter switch helps immensely when positioning the rotor. The two terminals hook directly to the starter.
If the engine has been disturbed, it must be brought to TDC on the Number One cylinder before you install the distributor. To do this, remove the Number One spark plug and disconnect the coil wireor on HEI distributors, disconnect the 12-volt lead from the distributorand...
...slowly crank the engine while holding a finger over the spark plug hole.
Turn the engine until compression is felt and the timing mark reaches the initial timing setting read on the timing tab.
Now install the distributor with the rotor pointed slightly counterclockwise from straight ahead.
After the housing has seated, the rotor should point straight ahead.
With the wiring reinstalled, start the engine, then check and set the initial timing. CHP