10builder
Well Known Member
I'm encountering a subtle, pulsing engine surge at cruise and unable to determine the cause. Here are the specifics:
O-320-B2B (160HP w/950TT) with only 12 on this new airframe. (Engine came from a 1974 PA-12 Super Cruiser)
Superior Millennium Cylinders
MA-4SPA carb (~300 hours since rebuild, p/n 10-3678-32)
Twin 4373 Slick mags (SB's current - just back from Champion)
Performance Propeller USA FIXED PITCH wood prop (68x68 picked up used here on VAF)
New engine driven fuel pump with a backup Facet provided by Van's
Red cube cabin side with no bends within 6" of inlet or outlet (fuel flow calibration in progress).
Van's FAB purchased from and installed per Van's
During cruise at around 2500 MSL, 2400RPM and 19.8 inches I can feel the subtle surging and able to make it completely subside (go away) by leaning the mixture. In contrast i did an in-flight mag check and it really only magnified the problem. I've seen references to re-jetting the carb but can't resolve in my mind how that relates here. (Photo attached of cruise parameters. BTW, the left fuel tank isn't empty, but rather the level occasionally drops out due to bad connection somewhere).
O-320-B2B (160HP w/950TT) with only 12 on this new airframe. (Engine came from a 1974 PA-12 Super Cruiser)
Superior Millennium Cylinders
MA-4SPA carb (~300 hours since rebuild, p/n 10-3678-32)
Twin 4373 Slick mags (SB's current - just back from Champion)
Performance Propeller USA FIXED PITCH wood prop (68x68 picked up used here on VAF)
New engine driven fuel pump with a backup Facet provided by Van's
Red cube cabin side with no bends within 6" of inlet or outlet (fuel flow calibration in progress).
Van's FAB purchased from and installed per Van's
During cruise at around 2500 MSL, 2400RPM and 19.8 inches I can feel the subtle surging and able to make it completely subside (go away) by leaning the mixture. In contrast i did an in-flight mag check and it really only magnified the problem. I've seen references to re-jetting the carb but can't resolve in my mind how that relates here. (Photo attached of cruise parameters. BTW, the left fuel tank isn't empty, but rather the level occasionally drops out due to bad connection somewhere).
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