I had a 1983 Cadillac with the 4.1 V-8 that had a belt driven vacuum pump to supplement manifold vacuum. I don't know how common that is, using a vacuum pump to supplement manifold vacuum on car engines, but the 4.1 came from the factory with such a pump. So . . . junkyards would be a good source of vacuum pumps although I'm sure one can find a more elegant solution to provide vacuum to drive whatever needs to be driven.
Keep in mind that you can use two external venturi tubes instead of one. I've seen planes with two. They're subject to icing as someone said . . . and that would happen right when you needed your vacuum instruments the most. In this era of AHARS I think I would bypass using vacuum at all. Vacuum pumps have always been the weak link in the system and venturi tubes are too vulnerable as well as causing drag. It's time to go with more reliable technology if you intend to actually use those instruments. Mike KSEE ____________________________________________________________ Fast, Secure, NetZero 4G Mobile Broadband. Try it. http://www.netzero.net/?refcd=NZINTISP0512T4GOUT2
