Original Design 4-Vane Vacuum Pump GETTING THE MOST PERFORMANCE FROM YOUR VACUUM PUMPS Moroso Vacuum Pump Nos. 22640 and 22641 can be driven no faster than 6500 RPM. The Moroso Vacuum Pump Nos. 22642 and 22643 can be driven as high as 8000 RPM. Moroso offers many ratio options for two reasons. First, by spinning the pump fast enough to achieve the desired vacuum at staging RPM is critical to getting the most performance from your vacuum system. Typically the amount of vacuum it makes below your staging RPM is not as important as it is when you are under a load and ready to make your run. Second, with engines that either run on alcohol, are supercharged or turbocharged, having the pump spin to maximum RPM to maintain vacuum is necessary in some cases. This will decrease the life of the pump, but will achieve the desired results. Versatile Billet Aluminium design, well suited for wet or dry sump applications Engineered vane material for improved efficiency and wear Completely rebuildable in 15 minutes Mounting bracket not included 4.150 O.D. body, 5.900 from back of pump to pulley mounting flange