How to Maintain the Carburetor and Fuel System (7)
Maximum performance cannot be achieved unless the carburetor is wide open when the throttle is pushed to the floor. Consequently, throttle opening should be checked regularly, immediately following any major changes in the engine compartment. Maximum airflow cannot be achieved if the throttle plates do not reach the wide-open position, or if it is pulled past wide open.
Maximum performance cannot be achieved unless the carburetor is wide open when the throttle is pushed to the floor. Consequently, throttle opening should be checked regularly, immediately following any major changes in the engine compartment. Maximum airflow cannot be achieved if the throttle plates do not reach the wide-open position, or if it is pulled past wide open. The throttle linkage should operate smoothly without binding and should be free of obstructions that may cause the carburetor to stick open. An auxiliary return spring MUST always be installed to insure that the throttle positively closes. It may be necessary to install a stop to prevent the carburetor from being opened too far and to prevent damage to the linkage. Take your time and set the linkage up right! Tuning linkage on sideways mounted tunnel ram carbs will take longer than a single 4 barrel.
Climate Changes and Performance
Changes in air density due to changes in temperature, barometric pressure, and humidity will have a direct impact on engine performance. As the air density changes, adjustments to the fuel mixture are often necessary. These factors can change from afternoon to evening. Everyone knows the engine will make more power at night when the air cools. The cooler, denser air carries more oxygen per cubic foot and thus support the capacity to burn more fuel. The weather conditions may not change enough from afternoon to evening to require mixture adjustments, but adjustments will certainly be necessary as the seasons change. Traveling to tracks in different climates or at different altitudes may also cause a need for fuel mixture adjustments. These factors cannot be overlooked when tuning for best performance.
Tuning With Spacers
Spacers and plenum dividers provide an easy way to change the configuration and the characteristics of the intake tract and the relationship it has with the carburetor. Adding a plenum divider to an open plenum manifold can help keep the left to right fuel distribution balanced for oval track applications This is especially helpful on alcohol engines.
Using spacers between the carburetor and intake manifold can produce dramatic results. The use of a four-hole spacer can improve low end to mid-range by helping the carburetor draw and atomize fuel. An open center spacer increases the plenum area and can benefit the mid-range and upper rpm power. It is not uncommon to see combinations of spacer types or stacking of similar type spacers being used.
The actual results from any spacer or combination of spacers can only be measured during a test and tune session on the specific engine combination being run. This information can be a very useful tool when tuning to find the best horsepower or to change the power characteristics to suit a specific track condition.
For consistent performance, a carburetor must be kept clean. Spray the air bleeds with carburetor spray or WD-40 every week. Air bleeds become clogged from dirt and dyes in the fuel. Clogged or dirty air bleeds can cause a stumble or a high- speed miss in an otherwise perfect carburetor. If you are putting the car up for the winter, use this little trick. Spin the engine over with the ignition off and the throttle open and spray of WD-40 liberally down the venturi will leave a fine mist of protection on the valve seats and cylinders to prevent rust. Finally, your carburetor should be rebuilt at least once a year and more frequently if itęs operated in dirty conditions.
Applications running alcohol require additional maintenance beyond that of a gasoline fuel system. Alcohol, being extremely corrosive, should not be left in the fuel system or carburetor for an extended period of time. Proper care includes draining and flushing the entire fuel system, usually with gasoline. The most common method is to drain the system and add gasoline to the fuel cell allowing the pump to draw fuel through the lines and to the carburetor. Alcohol carburetors are much richer than gasoline, so when the engine begins to idle and die, the system is pretty well flushed. If your sanctioning body allows the use of fuel additives, always use an additive that lubricates the fuel system for protection while racing.
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