Setting Timing and Advance
Setting the timing in your race engine can affect the efficiency of your ignition system. There is a way to set the timing, perhaps different from the method your team uses, that will assure the proper timing advance at top engine rpm.
Many teams will set the low-speed timing and then perhaps check the high-speed timing with any advance timing the distributor provides by revving up the motor to a high rpm. If at some point in the future the advance timing changes, and it can with mechanical systems, then we won't necessarily have the proper high-rpm timing we need.
We need to run the engine up to an rpm that is just above the point where the maximum high-speed advance is activated, and set the total timing we will need before top dead center (BTDC). Then, at the lower rpm ranges, the timing advance will be deactivated and the engine timing will be retarded by some number of degrees. This low-speed timing is not as important as the high-speed timing. The only reason we need less low-speed timing is so the engine will start easily.
Many distributors have a mechanical advance mechanism that may not be totally reliable for the advance curve. Therefore, we cannot count on the distributor adding a constant number of degrees of advanced timing to the low-rpm timing. When we set timing with full advance, whatever that may be at any given time, we are assured of the correct high-speed timing when the engine is at race-speed rpm.
Cooling Fan Techniques
Many racing engines do not need a cooling fan. Some need the fans only at lower rpm and need for them to be less efficient at higher rpm. Running a fan uses up some of the available engine horsepower. The idea is to run the fan only enough to cool the engine.
Some believe that having a high water temperature creates the need for a bigger and more efficient fan, when the real culprit is that the flow of water through the radiator is too fast to enable proper cooling. The radiator needs time to draw off the heat from the coolant. If we do not restrict the flow of coolant by use of a restrictor inserted into the system, we may never be able to lower the water temperature to an acceptable level.
A stock water pump is designed to run at 3,000 to 4,000 rpm-not at or above 6,500 rpm, as in racing applications. When we spin the water pump that high, we are forcing even more water through the system at a higher velocity, draining even more horsepower. There are several things we can do to help this situation.
By installing a larger pulley behind the fan, we can alleviate the drain on horsepower while slowing the flow of water through the engine. This slows down the rotation of the fan and the water pump, which both drain horsepower. Less drag from the fan and a slower flow of water helps the radiator do its job and can mean an additional 10-20 hp going to the rear wheels.
Exhaust Header Design for More Horsepower
The diameter of the header tubing must be correct for the size and design of the engine in order to produce maximum torque and horsepower. Installing the largest header tubing will not necessarily yield the best power numbers. Consult your engine builder for information on the best header design to use. Better yet, send your headers to be used when the engine is on the dyno.
Always tie together the two sides of the engine with a crossover tube. This connection should be located within 30 inches of the collectors that are located at the ends of the headers for improved scavenging effect.
Coating the headers actually gets rid of the heat of combustion faster and moves it out of the pipe to help cool the engine as well as the engine compartment. Upon cool-down, the mechanic will notice that working around the coated headers is much easier because they cool much faster.