Originally posted by J. Robinson
Since you guys are on the subject of blowers, may be you can clear up something I have been curious about for years. Can someone tell me what the numbers mean? I know they were originally produced to use on GMC diesels. I've seen them range from 3-71 to 18-71. Obviously, the first number relates somehow to physical size, but how? Why do they all end with 71?
Actually, they don't all end with 71. GMC made other motors with blowers.

53.. 2.3.4.V6.V8.V12..
71.. 2.3.4.4Twin.6.6Twin.6Quad.8V.12V.12VTwin.16V.16VTwin
92.. 6V.8V.12V.16V..
110.. 6.6Twin..
149.. 12V.16V..
add to those Turbo .. Turbo intercooled .. Turbo aftercooled .. Turbo intercooled aftercooled ..
those are documented but may be a few others not certain if there was a 171, and there were some V71 Twins and Quads.. inline had High and Low blocks..
there were also V53 and 671 alloy block versions