If you have a dry vacuum pump, the carbon vanes don't like to go backwards and may bind and break. I haven't seen a 'coupe with a dry vacuum pump.
As a kid we ran irrigation wells with ford 300's and chevy 292s. When we shut them down, we'd bring them back to idle, and run slow enough that the centrifugal pump would stop pumping and drain before we shut down. If the engine/pump ever tripped, the water would run back down the well, spin the pump and engine backwards, maybe up 1500 rpm for a long few seconds. These had electronic ignitions and I don't remember damaging anything. One well had Minneapolis Moline engine that got a Magneto overhaul every few hundred hours... It was close to 100,000 hours when Dad retired. We changed oil only when the engine died for whatever reason or once a month - 744 hours on an oil change! Natural gas burns a lot cleaner than liquid fuels. Just top them up with oil twice a day with a sight glass on the oil pan. mitch Learn2fly www.chickashawings.com 2+2=4! http://www.myspace.com/pianomitch
