Owners manual

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Figure 13 Figure 14
1. Change pump shooters until the smallest diameter nozzle that provides the crispest response is found.
Figure 15
2. Then change the pump cams and locations until the right cam is found that provides even more response. (Holley® offers a
pump cam tuning kit part P/N 20-12)
3. Finally, change the pump shooter once again, until the crisp response is maximized.
NOTE: If a nozzle size is desired that seems “in between” the nozzle sizes provided, then the nozzle can be drilled to
the desired size by using a wire drill held in a pin vise.
4. At this point, there should be no bogs, flat spots or black smoke (indicating excessive richness) when accelerating at wide
open throttle from a standing start.
JETTING (MAIN JETS):
Due to varied applications that a universal performance carburetor will work with, a few tips on jetting are provided to help you
understand their purpose.
1. Out of the box jetting is extremely close for most applications.
2. Carburetors are calibrated at sea level. Decrease the jet size primary and secondary, one number for every 2000 ft.
increase in altitude.
3. Holley® jets are broached, flowed, and stamped according to flow rate. NEVER drill jets, as this seriously alters flow
characteristics. Stamped numbers are reference numbers and DO NOT indicate drill size.
4. In most cases it will be unnecessary to increase jet size more than four numbers greater than out of the box jetting.
Exceptions could arise when the carburetor is mounted on a very large volume, plenum-ram manifold.
5. Spark plugs provide the best indication of proper jetting. Consult an ignition manual for proper reading of spark plugs.