I have been playing with hot rod flathead Ford v8 for 55 years. I have been slowly building up a 3:71 gmc homebuilt blower for the past 2 years. The blower was disassembled,cleaned,new bearings,etc—-rotors pinned to shaft and reassembled( not by me, but a gmc mechanic with 50 yrs.experience). A mechanic friend(from Bosnia) took one look at the rotation(clockwise facing frt of engine) and said my drive being on the left side(facing the engine)) would pull air from the outside of the case and force it “down the middle” whereas if the drive were on the rt side(facing engine) it would “force the compressed air “ around the outer wall of the blower as it was meant to do. My question is “does it really matter if air is pushed thru the center2 rotors or is forced along the outside to ride down and around the walls as he says “this is the proper path of air.” Is he correct? Thx flatheadjohn47 in s.texas.
Look at this photo and then follow some other comments in the rest of the thread. Your Bosnia buddy knows what’s up.
I just need a “correct” reply. Yes or no —-does it matter which direction the air travels? I realize it is getting compressed from both travel directions—-is one way better or more efficient than the “wrong “ way? Thx John in s.texas!
Left side drive as pictured would try to suck air out of the engine. The engine wouldnt run, but you would have really good intake manifold vacuum!
The blower, as pictured by the OP in post #1, turning clockwise will NOT force air “down the center of the engine “, it will force air out of the top of the blower case. Lippy’s post #10 above, posted while I was typing, illustrates the direction of air flow based on correct rotation. The GM 71 series inline diesel engines were reversible as to rotation....but that was accomplished by swapping the parts on the ‘front’ of the engine block to the ‘back’ of the block and vice verse. The block was symmetrical and when turned end for end the effect was as if rotation were reversed...but in fact the crank turned the same direction in relation to the block as before, but rotation was reversed in relation to whatever it was powering.
flatheadjohn47, The center area of the blower only acts as a seal. the outer area is the pump, so yes it matters! If you spin it backwards, it will suck on the cylinders. Edit: Lippy's picture shows it all!
You know they work the same as oil pumps. Using a drill motor, try driving your oil pump backwards and see how long it takes to build oil pressure.
I took my blower back to the man who assembled it(had no contact with him in 5 years) and we pulled the two gears in frt(have to pull both gears at same time to keep from binding up) and swapped place so now all is correct with the 3:71 gm and air is pulled around the outside of the rotors as it should be. Thanks to all that responded. The “drive” is now on the right side of the blower when looking at the Frt of the engine.Flatheads Forever!
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