Instructions for mechanical advance curve changes
The factory installed mechanical advance is set at 12° distributor (24° crankshaft). The mechanical advance plus the initial setting determines the total number of degrees of spark advance. For example, standard mechanical advance of 12° (24° crankshaft) plus 10° of initial setting would equal 34° total crankshaft spark advance (34° BTDC). The actual amount of spark advance is determined by engine requirement, and the total advance should not exceed engine builders specifications.
To change the advance curve in your new distributor, you may either leave the distributor in the engine or remove it to a bench.
1. By using the diagram (Figure 3), determine which hole the stop screw should be located in and which direction the arrow should be pointed for your distributor advance specification. For example, if you require advance of 14° (28° engine) and your distributor is right-handed rotation(clockwise), the stop screw would be placed in the bottom hole marked 14° and the "S" plate will be installed with the arrow pointing to the 10° - 13° indication on the stop bracket. If you need to change from the factory setting, proceed.
2. Remove the two screws holding the distributor bowl to the lower shaft housing and remove the distributor bowl.
3. Remove the two advance springs
4. Bend the ears back on the locking tab and remove the center nut. Lift the entire advance assembly out if necessary.
5. With the advance assembly placed in the proper location, replace the center nut and secure the locking tabs. Replace the advance springs. Bending tabs in will start the mechanical advance at a lower RPM. Bending tabs out will delay the start of the mechanical advance. the advance mechanism should move freely and have a minumum amount of end play without binding.
6. Reattach the upper bowl to the lower shaft housing. Be sure that the tangs in a lower assembly mesh properly with the tangs in the distributor bowl and check for rotor position. Install the two screws.
7. Install distributor in engine and set timing as per "Installation Instructions"