Power timing your Atomic 4

When motoring along at Universal’s recommended power setting of 2000 RPM, there’s a very precise time in the engine’s rotation when your ignition system must deliver a secondary discharge to each spark plug in order that the fuel/air mixture will ignite and develop its best (most efficient) combustion energy. This point in the engine’s rotation is usually expressed as a certain number of degrees of rotation before Top Dead Center (BTDC) of the piston at the flywheel end of the engine.

Distributors on both early and late model Atomic 4s have spring loaded flyweights which advance and retard the time of ignition as RPM varies. In a perfect world, if the timing were set to occur at cylinder number one TDC, the flyweights would advance the ignition timing to approximately 8 degrees BTDC at idle, and continue advancing to achieve the best performance up to a maximum advance of approximately 17 degrees by 2000 RPM and above. 

Unfortunately, the flyweights only sense RPM and not power, so in our less than perfect world, several variables including compression ratio (which varies when a head is milled or one head gasket is used instead of 2), fuel octane, overall condition of the engine, etc. come into play which will usually require a slight timing adjustment to obtain best performance at higher RPMs.

Power timing procedure:

Universal recommended a very simple three-step process for setting the timing on an Atomic 4 which is commonly referred to as “Power Timing.”  Steps 2 and 3 are copied directly from early Universal Owner’s Manuals:

1. Set the ignition point by having the points (or Ignitor) open precisely at TDC of the number one cylinder statically (before starting the engine).
2. Take the boat out for a trial run, and after bringing the engine to a normal operating temperature with the boat running at top speed, loosen the distributor clamp bolt and carefully advance the ignition timing by slowly rotating the distributor body counterclockwise until the RPM begins to fall off.
3. Then rotate the distributor body in the opposite direction (clockwise) to obtain the greatest RPM without rough running of the engine. Lock the distributor clamp in place.

Please note a small but important nuance in the procedure.  There is a small normal range of RPM between the ignition being set too advanced and being set too retarded.  After first finding the “too advanced edge” of this small normal range in step 2; step 3 has you finding the “too retarded edge” of the small normal range and lets you with the timing set in that position.  This small but important aspect of the Universal timing procedure alleviates the concern that the timing will end up being too advanced.

Watch video tech tip which where Don Moyer explains the entire power timing process, plus how to find #1 TDC.