Hey guys, looking at picking up a 4/71 GM blower for a far off distant future project idea i have....
But, i want to drive the blower from the flywheel end of the crankshaft on a holden six....For strange and unusual reasons known only to me.
So, the quick easy question that is likely to end in a long winded debate, can you reverse the rotation of a GM roots blower??
Obviously running it off the flywheel end of the crankshaft would make it spin backwards......Dont really need it sucking air out of the engine and blowing it through the carbie.....
GM blower stupid question
Started by
_Bomber Watson_
, May 19 2012 03:44 PM
38 replies to this topic
#2
_gensport_
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Posted 19 May 2012 - 05:47 PM
They definatly spin both ways, but the housings will probably support it better one way over the other. Without knowing the purpose..... what about shaft drive from the flywheel. That way the blower can be positioned where needed, and the direction can be easily reversed.
#3
_oldjohnno_
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Posted 19 May 2012 - 06:02 PM
But, i want to drive the blower from the flywheel end of the crankshaft on a holden six....For strange and unusual reasons known only to me.
Good to see you're still thinking outside the square Bomber, waaaaaay outside of it...
One of the features of the old GMs is that they could be configured in a million different ways. For example the head could go on either way around, so you could have the manifolds on the left or right hand side, and this of course meant that the cam and balancer shafts also had to be swapped over. Likewise, the blower, fuel pump, water pump, starter motor etc could all be mounted on either side, and there were also engines made with left hand rotation. All this made the engines easier to fit in but they were a parts mans' nightmare - a lot of the stuff like blowers and fuel and water pumps were made in left and right hand rotation versions that are interchangeable but aren't the same. I've personally fitted a fuel pump that did nothing but blow bubbles in the tank, and I've almost been caught out with water pumps.
All this is just the long way of saying that if you can track down the right blower you won't have to do anything to it.
Edit: sounds suspiciously like a boat engine to me...
Edited by oldjohnno, 19 May 2012 - 06:04 PM.
#4
_Bomber Watson_
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Posted 19 May 2012 - 06:04 PM
I see.
For clarification, mid mount ski boat.
So i need to look out for a factory reverse rotation gm blower?? Did they make the 4/71 in reverse rotation?? How do i pick the correct one??
Cheers.
For clarification, mid mount ski boat.
So i need to look out for a factory reverse rotation gm blower?? Did they make the 4/71 in reverse rotation?? How do i pick the correct one??
Cheers.
#5
limo
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Posted 19 May 2012 - 06:31 PM
I take you are driving prop off the snout, cranks tend to break at front with higher HP or shear keyways in my experience
why not turn motor around and use soft clutch and blower will be right?
why not turn motor around and use soft clutch and blower will be right?
#6
_Bomber Watson_
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Posted 19 May 2012 - 06:33 PM
Recon the engine would have to sit ultra high, and far foward, or i woould need a mega steep prop angle to run it the normal way around??
cheers.
cheers.
#7
dattoman
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Posted 19 May 2012 - 06:35 PM
My blower in my old SB ski boat was driven off the flywheel
Didn't seem to have any issues and made 'enough' boost
Email the blower shop and ask them
Didn't seem to have any issues and made 'enough' boost
Email the blower shop and ask them
#8
_mad350_
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Posted 19 May 2012 - 06:36 PM
or you can make a shaft that runs off the fly wheel that then runs to the front of engine and then run blower off that!
#9
_oldjohnno_
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Posted 19 May 2012 - 06:37 PM
If you hold the blower so that you're looking at the drive end and the inlet is at the top, if the driven shaft is on the right the rotation will be clockwise, it the driven shaft is on the left it will be anticlockwise. Just like a gear pump.
It may be possible to convert a blower by turning the end housing over and driving the other gear but I've never done it. I could have a look in my old Detroit manuals and see if it looks feasible.
It may be possible to convert a blower by turning the end housing over and driving the other gear but I've never done it. I could have a look in my old Detroit manuals and see if it looks feasible.
#11
dattoman
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Posted 19 May 2012 - 07:06 PM
Harrop blowers are shaft driven off pulleys at the back
Shaft runs thru to front of motor
Anythings possible
Bentley and MG stuck them out the front between the chassis rails
And this one has it out the front too
Shaft runs thru to front of motor
Anythings possible
Bentley and MG stuck them out the front between the chassis rails
And this one has it out the front too
#12
_Gunmetal LH_
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Posted 19 May 2012 - 07:08 PM
Can you swap the rotor gears over, and flip the snout?
Do the 4/71's have rectangle 'windows' for the inlet & outlet? Maybe just flip the whole thing?
Do the 4/71's have rectangle 'windows' for the inlet & outlet? Maybe just flip the whole thing?
Edited by Gunmetal LH, 19 May 2012 - 07:11 PM.
#13
_oldjohnno_
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Posted 19 May 2012 - 07:11 PM
I know ya want to
Cheers.
You can read me like a book...
Just had a look and only got 53 series here at home, pretty sure I have 71 and 92 at work though. The more I think about it the more I think it'd be pretty easy to do even with the "wrong" blower. They generally have another opening in the cover thats in front of the non-driven shaft and this is used to drive the fuel pump or governor. There's no reason this couldn't be used as a drive so long as the outboard bearing adjacent to the pulley was well supported. If the "snout" was reasonably long you wouldn't need a bearing at all at the blower end.
#14
_Bomber Watson_
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Posted 19 May 2012 - 07:53 PM
Looking at a 8v92 i have here, It looks like the front cover could be flipped over....
Then swap the gears as mentioned above and wala??
I dont have it in my hands, or i'd have something worked out by now lol, was hoping someone would know.
Cheers.
Then swap the gears as mentioned above and wala??
I dont have it in my hands, or i'd have something worked out by now lol, was hoping someone would know.
Cheers.
#15
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Posted 19 May 2012 - 08:17 PM
Looking at a 8v92 i have here, It looks like the front cover could be flipped over....
Then swap the gears as mentioned above and wala??
Cheers.
That'd be the simplest way, and if it looks like it'd work with the 92 it should also work with a 71, they are much the same. Just be aware that you'd have to realign and re-dowel the cover to the case to make sure the openings line up exactly with the shafts. You'd have to re-time the rotors after swapping the gears.
Edited by oldjohnno, 19 May 2012 - 08:19 PM.
#16
_Bomber Watson_
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Posted 19 May 2012 - 10:35 PM
Yeah this blower isnt set up for petrol (or methanol in this case likely) use yet, still ala strait off a diesel, so needs to be set up anyway, probably just going to pay someone to do it, unless someone can convince me its not hard. If its as simple as telling them i want to spin it backwards and them spinning the front cover around and swapping the gears then thats no issue.
Cheers.
Cheers.
#17
limo
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Posted 20 May 2012 - 01:02 AM
how long is your boat?Recon the engine would have to sit ultra high, and far foward, or i woould need a mega steep prop angle to run it the normal way around??
cheers.
I have done it with 202s , 308s and 350s in 18 ft ski boats. angle about 13 degrees from memory.
lash out and get a V drive
#18
_Bomber Watson_
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Posted 20 May 2012 - 01:29 AM
Well its not my boat atm, as said in the first post its a far off distant project....But yeah one of these
Glen L Craclkerbox boat design, send them money, they send you plans......
15ft nominal, can be strethced to 16ft. Buy the plans, build it from scratch, sounds like my kinda shit TBH but its screaming for the engine cover to be #@$^%& right off and a roots blown 202 sticking throught with header pipes running out over the wale. Yes im intending on wearing earplugs whilst driving it lol.
V drive isnt really an option, A for that base plan im going to have an engine sitting beside me, B even if i moved the cockpit foward that would frOck up the balance of the boat.
Short of finding a V drive boat minus engine, i dont really see any way to run a V drive. Boat hul design seems to be rather extreme, to the point a mid mount boat the lfattest part of the hull will be in the middle, v drive with teh engine in the back the flattest part will be at the back, etc etc, flattest part must be where most the weight is, i dont trust myself quiet enough to redesign a hull for that application.....And plus, that boat looks so frOcking tough as a mid mount.
That said i agree 100% with your reservations on running any form of hp through your average snub drive dog box type thing, and tbh the roots blower etc will be mostly for phwoar factor, i know i can get more hp using a turbo, but it wouldnt look as cool.....I just need engouh hp to go out and piss off dickweats in there $40k malibu ski boats.....I already can do that with my bit of crap clunker ski boat i have now........So its not hard locally lol.
Cheers.
Glen L Craclkerbox boat design, send them money, they send you plans......
15ft nominal, can be strethced to 16ft. Buy the plans, build it from scratch, sounds like my kinda shit TBH but its screaming for the engine cover to be #@$^%& right off and a roots blown 202 sticking throught with header pipes running out over the wale. Yes im intending on wearing earplugs whilst driving it lol.
V drive isnt really an option, A for that base plan im going to have an engine sitting beside me, B even if i moved the cockpit foward that would frOck up the balance of the boat.
Short of finding a V drive boat minus engine, i dont really see any way to run a V drive. Boat hul design seems to be rather extreme, to the point a mid mount boat the lfattest part of the hull will be in the middle, v drive with teh engine in the back the flattest part will be at the back, etc etc, flattest part must be where most the weight is, i dont trust myself quiet enough to redesign a hull for that application.....And plus, that boat looks so frOcking tough as a mid mount.
That said i agree 100% with your reservations on running any form of hp through your average snub drive dog box type thing, and tbh the roots blower etc will be mostly for phwoar factor, i know i can get more hp using a turbo, but it wouldnt look as cool.....I just need engouh hp to go out and piss off dickweats in there $40k malibu ski boats.....I already can do that with my bit of crap clunker ski boat i have now........So its not hard locally lol.
Cheers.
Edited by Bomber Watson, 20 May 2012 - 01:31 AM.
#19
warrenm
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Posted 20 May 2012 - 09:10 AM
Sounds like a great project. Try Jeff Ramsay Engineering 0296365539. He use to own the blue EH that that Normie Stewart(son of the late Mark Stewart)run last year at the 6 bangers.
#20
_oldjohnno_
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Posted 20 May 2012 - 10:08 AM
i know i can get more hp using a turbo, but it wouldnt look as cool.....
Apart from the looks factor a turbo would be absolutely perfect. Maybe you could go the other direction and mount the turbo low and out of sight then fit up a dummy single barrel strommie and grandpa spec air cleaner, 149 stickers on the rocker box etc. That'd really get up the noses of the Malibu guys when you cruise past them...
#21
limo
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Posted 20 May 2012 - 06:51 PM
Z drive, set motor at prop angle, soft clutch then bolt box to bell housing, in at top out at bottom couple to shaft and out under seat
Haines Hellier used to make a box that could be used as V or Z
VW combies had step down boxes in each axle (Z drives) we used to use them in race boats,
racing skiffs and some hydros back in 60/70s used Z drives, that boat is basically a Skiff
local guy in here made them using duplex chain and cogs, he cast up ally housing 2 halves the same and bolted together, could vary number of teeth and have step up
had one in my shed for ages but sold it few yrs back
Haines Hellier used to make a box that could be used as V or Z
VW combies had step down boxes in each axle (Z drives) we used to use them in race boats,
racing skiffs and some hydros back in 60/70s used Z drives, that boat is basically a Skiff
local guy in here made them using duplex chain and cogs, he cast up ally housing 2 halves the same and bolted together, could vary number of teeth and have step up
had one in my shed for ages but sold it few yrs back
#22
_Bomber Watson_
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Posted 20 May 2012 - 07:06 PM
Thats interesting....very interesting. The plot thickens.
I did have a look at a crank today and agree the snub isnt really a strong looking part, probably good for running some accessories and holding the balancer, as its designed for......
Then i had the crazy idea of grafting a flexplate to the crank snub. to start the engine....Could bolt a torque converter to it and have a monster fluidampner!!!!!
Even went to the point of deciding i could cut the back off an old crank, machine the ID out to go over the snub with a keyway, bolt through the end.......
I'll stop being silly now....Although i see no reason why that wouldnt work lol
Cheers.
I did have a look at a crank today and agree the snub isnt really a strong looking part, probably good for running some accessories and holding the balancer, as its designed for......
Then i had the crazy idea of grafting a flexplate to the crank snub. to start the engine....Could bolt a torque converter to it and have a monster fluidampner!!!!!
Even went to the point of deciding i could cut the back off an old crank, machine the ID out to go over the snub with a keyway, bolt through the end.......
I'll stop being silly now....Although i see no reason why that wouldnt work lol
Cheers.
Edited by Bomber Watson, 20 May 2012 - 07:08 PM.
#23
orangeLJ
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Posted 21 May 2012 - 09:05 AM
I'm worried about you DJ,
With all these crazy plans and projects, I'm beginning to think you have too much free time all of a sudden...
Have you given up masturbation? lol
With all these crazy plans and projects, I'm beginning to think you have too much free time all of a sudden...
Have you given up masturbation? lol
#24
_Bomber Watson_
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Posted 21 May 2012 - 06:27 PM
Yes Chris cut back to four times a day, so much more time!!!!
I said up top far off distant project, i just think to much, and never frOcking stop thinking, thats why i go to bed at 9.30pm and im still awake at 1am every frOcking night, its a PITA.
Cheers.
I said up top far off distant project, i just think to much, and never frOcking stop thinking, thats why i go to bed at 9.30pm and im still awake at 1am every frOcking night, its a PITA.
Cheers.
Edited by Bomber Watson, 21 May 2012 - 06:27 PM.
#25
_nzstato_
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Posted 21 May 2012 - 07:06 PM
Damn you bomber, now I've been looking at that site dreaming of boats. Though it has always been a dream of mine to build a boat from sratch. Though I think I take the path of using a proper propulsion system (i.e. a jet unit)
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