I have a 1973 motorhome 440 with low miles. I opened it up and checked all clearances and all was well within specs.

At idle, it has a whine like a turbine or blower like sound. As soon as its off idle (700 rpm) it goes away. I removed all the belts to confirm its not alternator, water pump or power steering pump.

Anyone have this experience and what was causing it?

Thanks in advance, Mike