Question about 8-71 / 6-71 blower?

Question

Were either of these originally GMC blowers? If not, please explain their orgin. I'm hoping they aren't, because I want to find a large supercharger of the same size with 2 carbs for a Ford engine, with no relation, direct or indirect, to GMC products. I really want no part in Ford engines that have GMC parts, it's just not right. Also, I need the name of any company that makes original blowers for Fords.

Answer 1

GMC blowers were frequently original equipment on large diesel bus engines; “GMC” is General Motors Coach Division.

    The numbers by which they are frequently identified contain a code as to the original application: the engine for which it was designed, and some information as to the pumping capacity of that model. There are 3 common rotor diameters, and up to 7 case and rotor lengths in some types.

    The prefix is the case length (3-, 4-, etc.).

    The suffix indicate inches per cylinder on the original installation motor (-53, -71, -92), and determine the rotor center to center distance and case width.

    The actual supercharger displacement is less than the engine size; an original GMC 6-71 transfers 339” per revolution, a Weiand 6-71 replica 411”, a Weiand 8-71 replica 438”.

    The rotor length is not directly proportionate to capacity: the 6-71 rotor is 15” long, the 8-71 rotor is 16” long, the 16-71 rotor is 20” long.

    The helix angle of the original -71 series is 30°; aftermarket superchargers are frequently pitched at higher angles.

    Although frequently used to supercharge V8 engines, none of these were originally made for this purpose. The most frequently used size for street engines are 4-71, 6-71 & 8-71. Aftermarket replicas are made in even larger sizes.  Even the smallest of these (3-53) is very bulky and inefficient compared to more modern designs such as the Eaton.

    The name “GMC” or “Jimmy” has become generic, including the common automotive and industrial BDS, Dyer, GMC, Hampton, Mooneyham, Littlefield.

Answer 2

Well, if you don't want anything on a Ford that has a direst or indirect connection to GM, GOOD LUCK is all I can say. Ford, GM and Chrysler (and every American car company before them) has farmed out manufacture of lots of components, including trannys and rear ends, steering boxes, carbs, ignition systems, etc. The 6-71 style blowers made today are replicas of the original GM units, they use the same style drive and compressor system, but are not related to GM except in name.

Note to UDUMFUK - very appropriate name, given your answer. Detroit Diesel, or 'jimmy' engines were made by General Motors. In 2000, they sold the diesel engine division to Daimler Chrysler, but in the days of the  -71 and -53 series engines, it was GM all the way.  

Answer 3

both were GM truck parts but any modern blower is aftermarket NO ONE uses old GM blowers.  Magnacharger...try looking up Supercharger on yahoo or google...and try a new attitude...it doesnt matter who makes it...good parts are good parts..thats why many GMs have 9 inch ford rearends...

Answer 4

Paxton and Eaton make Ford blowers

Answer 5

they were called 6-71 blowers and used in marine applications, They were called jimmys and so every one thought they were a gmc application when in reality its the name of the company and they had they on every thing from ford to international gas and detroit gas engines. they are the ones to use and they are not a gmc product