Inliners International Forums General Discussion Blown and Injected V8-71/92 blowers

Does anyone know the difference between a V8-71 and V8-92 Blower? No speculation please, just facts. Thinking in terms of boost at 1:1 off the front of the crank. Thanks.

The bower I'm curious about is the PN 8921938 Detroit Diesel 8V71, 8V92 Blower Assembly

AFAIK those are physically very different from the common 671 etc. There are no aftermarket parts, manifolds, drives etc. It may work but you'll have to make most of it yourself. That's the reason you don't see them.

Vintage racing is like that, no aftermarket parts, make it yourself but that's half the fun! The other half is when it works. The V type actually works better for my application. It's the size differences that worry me. Driving off the front of the crank, Potvin style has it's own set of problems and virtues. One ratio, the size of the blower determines the boost, all things being equal. Helps with the harmonics.

For those too young: Potvin made a front drive located at crankshaft height and driven off a nose extension at 1:1 ratio. This was used in big sports and racing cars (although not Potvin) including Bentley. For a V8 the blower case is rotated 90°, with the inlet facing left (with the injection or multiple 97s) and the discharge facing right feeding 2 long aluminum tubes ending at the V8 engine's manifold.
The idea was the reduce the aero signature (no giant mailbox on top), but as Armond said the blower delivery is limited to blower displacement (rather than a ratio change).
There are opposing views on exactly how much air is transferred by a GMC roots, the official version is that "6-71" means 6 cylinders × 71 inches = 426" per revolution.

[img:left]https://www.jalopyjournal.com/forum/attachments/crankdrive-fuel-pump-jpg.945547/[/img]

The actual drive is probably not around (if even made for these engines) but not difficult in an engineering sense. Under $100 will buy all the parts, the method of attaching the drive to the crank and blower rotor are the puzzle.
2 roller chain sprockets, I suggest #50 (a.k.a.530 single row), tooth count 17 minimum, 60 maximum but obviously limited to what will interfere with something.
1 length of quality #50-2 (double row) chain = to the circumference of one sprocket.
1 sprocket is attached directly to the crankshaft nose (like any blower drive, keyed, tapered, whatever).
The other sprocket is attached to the drive end of 1 rotor.
The chain has one row of rollers on each sprocket, face to face.



This is 100.000% accurate, only needs to be greased, very durable (nervous? Use #60 chain), weighs almost nothing, and yet allows for very small vibration, misalignment etc. that would break a "greek" (male-female) coupler.

Thank you Panic. I've made some headway in finding out about these blowers. The turbocharged 8v-71 and the 8v-92 both used the same blowers as the turbo made up any differences and a roots blower was needed only to start the engines. These blowers are 83% the size of a normal 8-71. I have ordered a 8v-92 from Deans Blowers with a reversed rotation so the inlet will be on the passengers side and outlet on the drivers where the intake ports are. I also spent some time researching chain couplers and lovejoy's. I decided against the chain coupler because of the RPM and harmonics. A lovejoy L225 with a Hytrel solid center spider. to this a sleeve to cover the spider and prevent it from escaping RPM will be added.