What could cause this? A whirring, whining noise sounds from the accessory case of a new 375.
Knowledgeable individuals who've heard this say it's not right; I couldn't agree more. Offhand, bearings are dismissed since it's not so much a screeching metallic howl from the engine as gears that aren't properly messed. Frequency modulates with RPM (as you would expect), lowest easily imagined as the teeth engaging - a very fast buzzing - progressing to a smooth whirr then steady whine above 1500 rpm. Think noisy automotive differential.
It's not the ignitions, governor, or alternator; there's no vacuum pump. One fellow says he "feels" it when touching the oil filter and left ignition (P-mag), nothing on the right ignition. We've yet to put a stethoscope to it. Interestingly, the mag gears only engage .15 inch - that's less than half a tooth width - yet I'm told within spec.
From what I read, there are no mesh or lash adjustments in assembling the accessory case. So far, the only thing we can conjure is a canted bearing counterbore that puts the unfortunate gear slightly out of the rotation plane.
Since the engine builder must rely on our description, they're in no better position than the VAF Brain Trust. What do you think I'm dealing with?
John Siebold
Knowledgeable individuals who've heard this say it's not right; I couldn't agree more. Offhand, bearings are dismissed since it's not so much a screeching metallic howl from the engine as gears that aren't properly messed. Frequency modulates with RPM (as you would expect), lowest easily imagined as the teeth engaging - a very fast buzzing - progressing to a smooth whirr then steady whine above 1500 rpm. Think noisy automotive differential.
It's not the ignitions, governor, or alternator; there's no vacuum pump. One fellow says he "feels" it when touching the oil filter and left ignition (P-mag), nothing on the right ignition. We've yet to put a stethoscope to it. Interestingly, the mag gears only engage .15 inch - that's less than half a tooth width - yet I'm told within spec.
From what I read, there are no mesh or lash adjustments in assembling the accessory case. So far, the only thing we can conjure is a canted bearing counterbore that puts the unfortunate gear slightly out of the rotation plane.
Since the engine builder must rely on our description, they're in no better position than the VAF Brain Trust. What do you think I'm dealing with?
John Siebold