gm superchargers

[Russ]

anyone know anything about the old style GM blowers . I got given one but i have no idea, i got told it was a 14/91 or something like that. Its body is as long as a windor block?

any info would be appreciated.

[Glenn 'Stinky' Stankevicius]

14/91 would be a huge blower, most common on "street" cars with Chev SBs are the 6/71, 8/71s for BBs.
I think the drag racers have something like 14/71s, don't quote me though.
The capacity of the blower is supposed to be related to the model number eg 6/71 is for a 6cyl with 71 cubic inches per cylinder or something like that. I have heard of 4/71 and I think there is even a 4/56 baby blower, AFAIK all were designed for Chev's Truck motors.

WTF are you doing with a Windsor block anyway? 

[oldjohnno]

I've been working on these old 2 stroke GMs for many years. They have been known as Detroit Diesels for a long time now, though many of the old timers still call them GMs and the basic design goes back to the late 30s. The modern Detroits are completely different 4 stroke engines. Stinky is right; the first number refers to the number of cylinders and the second the capacity of each cylinder. Common capacities are 53, 71 and 92 cu in/cyl. There is a bigger one too (149 cu in I think) though I've never worked on those. Common configurations are straight 3, 4 and 6cyls, and vee 6, 8, 12 16 and 24s. Some of the bigger motors are made by bolting two or more blocks/cranks together and use two individual blowers, often with two heads per bank as well. The 53, 71 and 92 engines all use different size blowers, and the inline blowers are different to the vee engine ones. I've heard hot rodders refer to 14:71 blowers too even though no such engine exists and suspect it may be a term coined by the US race blower builders.
If you measure the rotor diameter and length I could probably work out what it came from. They aren't that hard to rebuild if you're careful, I could probably email scans of the relevant manual pages if you need them..

[oldjohnno]

I should have added that the little 6:71 blowers are plenty big enough for a street small-block, so assuming the "14:71" is an big blower based on the 71 series unit it would probably be grossly oversized..

[Russ]

just measured the rotors this morning, they measure:

Radius 75mm (3 in).
Length 403mm ( 15 7/8 in)
and it has three veins per rotor with a 120 degree twist.

apparently it was off a 10 litre 2 stroke.

I know it is grossly oversized for just about anything but it would just look nasty and very much a rat rod thing.

Being a bigger capacity pump wouldn't that mean it wouldn't have to spin as fast to get the same pressure as a smaller one? albeit a lot less efficient

Ta Russ

[oldjohnno]

Ok I'll check those measurements when I go back to work next Monday.. Once we know what it is it shouldn't be too hard to work out a drive ratio..

[Russ]

correction that was a 60 degree twist on the roters.

and stinky the windsor block is for my ski boat and it is soon to have a very large and mostly usless blower on it. but hey its a ski boat.

[Ed]

Russ,
We need pics of this grossly oversized Blower, also of the boat too!
Cheers
Ed

[mikey]

Yeah oversize is ALWAYS better. The bigger the cam the better I always say.  

[Russ]

the boat is still in the other stuff for sale page, dont know how to post a link, its under lewis ski boat or something.

when i get my act together and if it ever stops raing up here ill mock up the block with the clevo heads and blower to get a pic.

how are those numbers coming johno?

[mikey]

Hey Russ,
                This is how you post a link, copy the text in the address bar at the top of your browser and paste it here.

Obviously copy the text when you are on the actual page that you want to post info about. Example if you want to show a particular car for sale you need to go to that webpage and copy that text, I have copied the text from this page when I was reading your post so if you click it you will end up at the same place

http://fefcholden.org.au/forum/index.php/topic,12433.msg75161/topicseen.html#new

[Russ]

Cool cheers mikey,

adding a link is to easy, here it is.
http://fefcholden.org.au/forum/index.php/topic,10043.0.html

The motor was going to go in my other fc but my mates  hate the idea of either wasting a ford donk on a holden or wasting a holden with a ford donk...... it might be better to put some jap crap in instead.. na just joking  .

Russ

[Russ]

If any one is curious the blower has been identified as a 8V92 (same length but flater than 8V71) and it pumps aproximatly 400 ci of air/rev which means on a 302 (151ci/rev) i can run 1:1 and get about 2 atm even if the blowers less than 80% efficient (which it will be). and parts and kits are still available for them as they are popular in the us and still in use in buses and boats today.