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John Moxon 
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[email protected]
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Location: Rialto. CA
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 Posted: Fri Nov 08, 2024 5:36 pm Post subject: Re: Shorrock C75BV on a Ghia Cabriolet in Australia |
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| sputnick60 wrote: |
I usually spend my time on the Ghia forum but that has to change now that I've acquired a Shorrock for my '66 Karmann. This had been a long time coming with many dead ends and diversions but finally a complete set up became available out of the UK. John Moxon helped to get this into my hands and it arrived in Australia during the pandemic. More delays ensued because I'm working in New Zealand and access wasn't possible with closed borders.
Since it was removed from a running 1300 beetle in the UK it is quite possible for it to go right on the car, but it looks a little bit aged and could do with a freshen up. It was also damaged in transit and for that some repairs are due.
First up is to show what I have and then to go about doing a full refurbishment of it and its appendages.
My ’66 is built with a 12 volt system. Originally a 6 volt car It was reasonable to convert to the higher voltage during a full full restoration. So to make the Shorrock work it needed a new 12 volt fuel pump. John organised that to come with the shipment and the old pump he managed to sell to someone who needed it.
There were two carburettors provided. One was right off the previous install and the other is a spare. we have a CD 150
I have to get a spare set of belts. These look like a Mintex CUPT374 and a Rootes 9926586. I've looked for those but can't seem to find them. If anyone knows better, do let me know what they are so I can order a set.
I have 2x manifold ends with blow off valves for 1300/1500
and the original rubber manifold couplings.
The blow off valves were seized and I spent a little time with them trying to unbind them. I removed them from the manifold ends
Then I sat them in the vice to try loosen them with some force. I used the handle of a small wooden hammer to push down on the internal piston.
But they wouldn't move until I put a small amount of machine oil on them and that loosened them right up.
I wiped them up and set them aside. Maybe some of you know if that is good enough or if more work is required to get them to spec. I suppose a pressure test of some kind to validate that they open at the right pressure would be something to do.
So here are the broken bits. Poorly packed in transit would be the root cause of that.
The VW stand is broken in one corner. This isn't a difficult TIG repair. There are lots of talented TIG welders out there.
More concerning is the cast iron pulleys both of which are chipped. I have the chipped piece from the larger pulley
The chipped piece is missing from the smaller pulley. I'd like to learn if there are replacements out there. Otherwise I'll have to find someone who can rebuild them.
There are also some studs that got bent in the move. I removed those without difficulty
I also removed the name plate off the unit. I cleaned it up and set it aside. I was amused that the Specification number was stamped upside down. Perfect for life in the southern hemisphere!
And finally a comprehensive series of photos of the blower itself
I have sat it on the bench with an electric drill to rotate it and it spins freely and provides quite a bit of suction at the input and blow at the output. Possibly I only need to do a cosmetic refurbishment but that's not really going to satisfy me. It will look odd going on a motor that was totally stopped down rebuilt and looks like new.
I plan to strip it down and have the outer case water blasted to give it a fresh out-of-the-casting look. All the studs, nuts and washers will be replaced. The same will go with the manifolds and the CD150s.
This will take a while since I'm hoping back and forth across the Tasman but I'm sure it won't take as long as the car to restore.
So stay tuned for the likely infrequent updates.
Cheers for now!
Nicholas |
I know this has nothing to do with this fourm but it got me thinking about these blow off valves on these shorrock supercharger...how would these perform... if one were to use them on a corvair turbo would I have to use the 2 shorrock blow off valves or only 1 for a 36hp corvair turbo setup ???? I've never seen anyone use these blowoff valves for a vintage turbo setup .... |
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thomas.
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| Posted: Wed Nov 13, 2024 2:43 am Post subject: Re: Shorrock C75BV on a Ghia Cabriolet in Australia |
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| On a draw thru. with the carb. before the supecharger it is my understanding that a pop off valve is not needed. I've installed various superchargers on draw thru set ups on 40hp & dual port & never used one. You could eliminate it if not worried about originality. |
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macdweal
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Location: Kuilenburg
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| Posted: Sat Nov 23, 2024 6:24 am Post subject: Re: Shorrock C75BV on a Ghia Cabriolet in Australia |
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| I think the pop off valve is for preventing the compressor going airborne in case of a backfire. |
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sputnick60
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wagen19
Samba Member
Joined: November 16, 2007
Posts: 643
Location: germany
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| Posted: Sat Feb 01, 2025 1:30 am Post subject: Re: Shorrock C75BV on a Ghia Cabriolet in Australia |
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| sputnick60 wrote: |
| macdweal wrote: |
| I think the pop off valve is for preventing the compressor going airborne in case of a backfire. |
Yes, that's what I've read too. To protect the vanes from damage. A backfire must have a lot of energy behind it I suppose.
Nicholas |
Good luck to all compressor junkies!
It´s a interesting field to "play" and combine with old VW technique.
Humourus thinking, remembering W.O. Bentley about the Birkin-Paget-project, the 4 1/2 l Bentley Blower.
On the positive side, while racing, more than one "fastest lap" was not achieved.
„to supercharge a Bentley engine was to pervert its design and corrupt its performance“
https://de.wikipedia.org/wiki/Bentley_4_%C2%BD_Lit...%E2%80%9C) |
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John Moxon
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wagen19
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Location: germany
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| Posted: Wed Feb 05, 2025 6:17 am Post subject: Re: Shorrock C75BV on a Ghia Cabriolet in Australia |
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| John Moxon wrote: |
Ahhh they were coarse Roots blowers.
These Shorrock Superchargers sip fuel like a Vicar at a summer tea party.  |
Thinking about the inner lubrication of all mechanical parts of the Shorrock Superchargers.
On paper and on pics here, I could not see a kind of oil or grease reservoir, or a lubrication system, as at the Judson for ex.
Is there a hidden or separate system for sipping oil to the mechanic, I still have have not been able to see?
OK, it´s written, the lubrication system is connected to engine, that seems to be the tiny hoses in upper pic.
What about total oil consumption of engine + blower?
What about the smell of exhaust fumes? Similar as old style 2 stroke engines like the german Trabant cars emitted? (or clouds of burnt "Rizinus", castor oil?)
Is it known, measured, how much, or how many hp the compressor needs to be driven under full throttle at engine rpm 2000, 2500, 3000, 3500, 4000 or more? |
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John Moxon
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| Posted: Wed Feb 05, 2025 8:38 am Post subject: Re: Shorrock C75BV on a Ghia Cabriolet in Australia |
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| wagen19 wrote: |
| John Moxon wrote: |
Ahhh they were coarse Roots blowers.
These Shorrock Superchargers sip fuel like a Vicar at a summer tea party. |
Thinking about the inner lubrication of all mechanical parts of the Shorrock Superchargers.
On paper and on pics here, I could not see a kind of oil or grease reservoir, or a lubrication system, as at the Judson for ex.
Is there a hidden or separate system for sipping oil to the mechanic, I still have have not been able to see?
OK, it´s written, the lubrication system is connected to engine, that seems to be the tiny hoses in upper pic.
What about total oil consumption of engine + blower?
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Oil consumption is small...it only needs a little to feed the main bearings. The Shorrock vanes get what they need from the mix with fuel but the Shorrock runs a lot cooler than the Judson as the vanes are not in contact with the casing. You see in the picture the oil feed is simply from an adapter fitted to the Oil Pressure outlet under the distributor to the back of the supercharger. You can adjust the flow of oil with a metered pin if you need.
_________________
John.
Judson Supercharger Information on The Samba
My 1958 Shorrock Supercharged Karmann Ghia
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wagen19
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Posts: 643
Location: germany
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| Posted: Wed Feb 05, 2025 1:06 pm Post subject: Re: Shorrock C75BV on a Ghia Cabriolet in Australia |
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| John Moxon wrote: |
| wagen19 wrote: |
| John Moxon wrote: |
Ahhh they were coarse Roots blowers.
These Shorrock Superchargers sip fuel like a Vicar at a summer tea party. |
Thinking about the inner lubrication of all mechanical parts of the Shorrock Superchargers.
On paper and on pics here, I could not see a kind of oil or grease reservoir, or a lubrication system, as at the Judson for ex.
Is there a hidden or separate system for sipping oil to the mechanic, I still have have not been able to see?
OK, it´s written, the lubrication system is connected to engine, that seems to be the tiny hoses in upper pic.
What about total oil consumption of engine + blower?
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Oil consumption is small...it only needs a little to feed the main bearings. The Shorrock vanes get what they need from the mix with fuel but the Shorrock runs a lot cooler than the Judson as the vanes are not in contact with the casing. You see in the picture the oil feed is simply from an adapter fitted to the Oil Pressure outlet under the distributor to the back of the supercharger. You can adjust the flow of oil with a metered pin if you need.
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Thank you for your pics and answer.
"Small" oil consumption is very relative, I guess and what about fuel?
Correct me please, I think, the blower is allways engaged, or is there a bypass and a kind of electric clutch, similar as on air condition? (A kick down switch and so on could also make sense, I think.) Sorry about my stupid questions, but with these superchargers I´ve no experience. What about high revs, when shifting next gear, while sporting? What displacement and cam does your engine have? Trans? |
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John Moxon
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| Posted: Wed Feb 05, 2025 1:37 pm Post subject: Re: Shorrock C75BV on a Ghia Cabriolet in Australia |
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| wagen19 wrote: |
Thank you for your pics and answer.
"Small" oil consumption is very relative, I guess and what about fuel?
Correct me please, I think, the blower is allways engaged, or is there a bypass and a kind of electric clutch, similar as on air condition? (A kick down switch and so on could also make sense, I think.) Sorry about my stupid questions, but with these superchargers I´ve no experience. What about high revs, when shifting next gear, while sporting? What displacement and cam does your engine have? Trans? |
These are low pressure superchargers. All the supercharger kits supplied by Judson, MAG, Pepco, Shorrock were intended for everyday use and to be fitted to you car at the weekend so you could drive your car to work on Monday.
They were configured to utilise your stock engine without the need to open the case. As kits their success was based on replacing as few parts as possible. This won't change your VW into a racecar.
Shorrock Supercharger Road Test
https://www.thesamba.com/vw/forum/album_page.php?pic_id=489935
https://www.thesamba.com/vw/forum/album_page.php?pic_id=489936
...then there's the question of where you're going to find a Shorrock Supercharger Kit??
_________________
John.
Judson Supercharger Information on The Samba
My 1958 Shorrock Supercharged Karmann Ghia
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wagen19
Samba Member
Joined: November 16, 2007
Posts: 643
Location: germany
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| Posted: Wed Feb 05, 2025 3:00 pm Post subject: Re: Shorrock C75BV on a Ghia Cabriolet in Australia |
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| John Moxon wrote: |
| wagen19 wrote: |
Thank you for your pics and answer.
"Small" oil consumption is very relative, I guess and what about fuel?
Correct me please, I think, the blower is allways engaged, or is there a bypass and a kind of electric clutch, similar as on air condition? (A kick down switch and so on could also make sense, I think.) Sorry about my stupid questions, but with these superchargers I´ve no experience. What about high revs, when shifting next gear, while sporting? What displacement and cam does your engine have? Trans? |
These are low pressure superchargers. All the supercharger kits supplied by Judson, MAG, Pepco, Shorrock were intended for everyday use and to be fitted to you car at the weekend so you could drive your car to work on Monday.
They were configured to utilise your stock engine without the need to open the case. As kits their success was based on replacing as few parts as possible. This won't change your VW into a racecar.
Shorrock Supercharger Road Test
https://www.thesamba.com/vw/forum/album_page.php?pic_id=489935
https://www.thesamba.com/vw/forum/album_page.php?pic_id=489936
...then there's the question of where you're going to find a Shorrock Supercharger Kit?? |
Dear John,
thank you very much for your answer.
My understanding is, the car feels smooth, has allways more torque, more peak, is never nervous. That all sounds very good.
Can the feeling be described, similar to a 1600 "B engine with a bit higher top rev? Around 50 to 55 hp?
Of course, a 1600 B-engine is technical totally boring, compared with a Shorrock blower.
My 50 hp bugs I had, nipped around 9 to 12 l per 100 km, my 34 hp bugs take 7 to 10 l. My 30 hp ovals in summer go 450 to 500 km before switching to reserve. On long distance trips I come around 520 km before reserve is needed. Cold weather: after around 400 km reserve is needed. The low compression 49 split, 25 hp with old 26 VFI mostly wants more fuel, so around 8 to 9 l.
So far, thanks again. |
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sputnick60
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| Posted: Sat May 31, 2025 4:02 am Post subject: Re: Shorrock C75BV on a Ghia Cabriolet in Australia |
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Some updates.
I went to a place called Greasy Hands which is a workshop space where you can rent time and access the machinery. I had to grind down the tines of my bearing puller to get a lift on the front bearing. This bearing wasn't installed correctly and was spinning in the front plate causing damage to the aluminium. I'll have to work out a fix for that later. Anyhow the bearing broke apart and I ended up getting sufficient purchase on the inner ring to hear that nice "click" as it finally let go.
From there I turned attention to the main body. I could pull the cotter pin
And then turn the nut to free the vane holders. This nut was only finger tight.
Here are the vanes, the trunions and the vane carriers as one assembly. I have to work out how to pull that stack of bearing without breaking any of the rivets or bending the vanes. Study time!
This is the view back into the C75B. Those counter sunk screws right up there back need to come out to access the rear bearing. Most were no trouble, but one is stuck and I've already stripped the slot. I'll try an easy out, or maybe a drill with a countersink bit to shear the head. It's a difficult to reach but at least it isn't the once next to the shaft.
I found this loose in the back, not sure where it came from. There were some other missing screws so maybe they ended up stuck in an inlet valve. Maybe this is all part of a disaster that prompted the previous owner to sell this one.
Fortunately the front and rear sections have these screw holes that permit controlled force to separate the faces. Would be nice if VW engine blocks had similar.
So here is the outer case separated with the rotor in the background.
I pulled all the studs since they were looking old and could do with a refresh. Some of the manifold studs were bent. Replace the lot I think.
That's all for now
Nicholas
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'66 Karmann Ghia Cabriolet...
'65 Porsche 356C Coupe...
2005 Mecedes Benz C180 Kompressor Estate
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sputnick60
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Joined: July 22, 2007
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| Posted: Sun Jun 01, 2025 12:12 am Post subject: Re: Shorrock C75BV on a Ghia Cabriolet in Australia |
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Some more photos of the disassembly. Here we see how the vanes and the vane carriers can pull apart.
You just pull them out sideways noting the carriers are interleaved. One vane has its carrier at the top and bottom, the opposite van has its carriers second from top and bottom. The third and fourth vane are almost the same but one is mounted the opposite way around. Between each section is a ~1/8" spacer and in the middle is a single wider spacer, about 1/4"
The parts laid out. I'll replace the 8 bearings which are a common size. Just have to make sure I don't get Chinese ones.
Nicholas
_________________
'66 Karmann Ghia Cabriolet...
'65 Porsche 356C Coupe...
2005 Mecedes Benz C180 Kompressor Estate
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John Moxon
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Joined: March 07, 2004
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| Posted: Sun Jun 01, 2025 2:35 am Post subject: Re: Shorrock C75BV on a Ghia Cabriolet in Australia |
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| sputnick60 wrote: |
Nicholas |
If anyone is wondering why the Shorrock Supercharger only appeared in the EMPI catalogue for just one year, (1966) the picture tells an important part of the story.
Answer: They didn't sell; purely on the price differential between the Shorrock kit and the Judson kit. As you can see the Shorrock is a complicated piece of engineering, the Judson, simplicity itself. You could buy the standard Shorrock kit for the 40hp for $395.00, the Judson $144.00.
However the Shorrock was built for reliability, the Judson for affordability.
_________________
John.
Judson Supercharger Information on The Samba
My 1958 Shorrock Supercharged Karmann Ghia
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wagen19
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Posts: 643
Location: germany
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| Posted: Sun Jun 01, 2025 4:26 am Post subject: Re: Shorrock C75BV on a Ghia Cabriolet in Australia |
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| John Moxon wrote: |
If anyone is wondering why the Shorrock Supercharger only appeared in the EMPI catalogue for just one year, (1966) the picture tells an important part of the story.
Answer: They didn't sell; purely on the price differential between the Shorrock kit and the Judson kit. As you can see the Shorrock is a complicated piece of engineering, the Judson, simplicity itself. You could buy the standard Shorrock kit for the 40hp for $395.00, the Judson $144.00.
However the Shorrock was built for reliability, the Judson for affordability. |
Humorous thinking:
simplify your life, use a set of larger (1500 S) pistons and a 69 mm crank.
In early 1966 there already were plenty of (used) 1300 ccm and much more 1500 ccm bus or type 3 engines, even the rather new 1600 ccm type 3 with dual port heads for the type 3 was on the market.
It was some years too late for an expensive blower for the old 1200 ccm engines!
(What would a used but good 356 engine with up to 95 hp that time have cost, after the 911 was on market since 1964?) |
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John Moxon
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| Posted: Sun Jun 01, 2025 8:21 am Post subject: Re: Shorrock C75BV on a Ghia Cabriolet in Australia |
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Yes alternatives have always been out there but the Supercharger Kits weren't aimed at the experienced enthusiast. They were aimed at "the average Joe" who wanted a bit of extra performance from an accessory kit he could fit in a few hours on a Saturday or Sunday and drive it to work on a Monday morning. 
...but we're not here to discuss the reasons why they failed to sell.
Sixty years later Nick has his Supercharger kit to restore to it's reliable working order. It's interesting to see its component parts...I've never seen the insides of mine in the 15 years it been running on my Karmann Ghia. 
_________________
John.
Judson Supercharger Information on The Samba
My 1958 Shorrock Supercharged Karmann Ghia
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wagen19
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Posts: 643
Location: germany
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| Posted: Sun Jun 01, 2025 12:08 pm Post subject: Re: Shorrock C75BV on a Ghia Cabriolet in Australia |
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| John Moxon wrote: |
Yes alternatives have always been out there but the Supercharger Kits weren't aimed at the experienced enthusiast. They were aimed at "the average Joe" who wanted a bit of extra performance from an accessory kit he could fit in a few hours on a Saturday or Sunday and drive it to work on a Monday morning.
...but we're not here to discuss the reasons why they failed to sell.
Sixty years later Nick has his Supercharger kit to restore to it's reliable working order. It's interesting to see its component parts...I've never seen the insides of mine in the 15 years it been running on my Karmann Ghia. |
OK, I agree.
It´s a chance to learn about that kind of Supercharger. Many thanks for the pics.
Today it´s worth and interesting rebuilding that rare masterpiece of vintage speed technic.
It´s much more about speed history and enthusiasm, than about hard performance ability or the budget of the "average Joe" in the sixties, as well as today. |
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sputnick60
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| Posted: Mon Jun 02, 2025 2:08 am Post subject: Re: Shorrock C75BV on a Ghia Cabriolet in Australia |
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| wagen19 wrote: |
OK, I agree.
It´s a chance to learn about that kind of Supercharger. Many thanks for the pics.
Today it´s worth and interesting rebuilding that rare masterpiece of vintage speed technic.
Its much more about speed history and enthusiasm, than about hard performance ability or the budget of the "average Joe" in the sixties, as well as today. |
Hi wagen19.
You mightn't know this Shorrock is for the engine my Ghia had from the factory. The whole car was restored and the engine fully rebuilt with the project finishing some 8 years ago. I could have built it with bigger cylinders and dual port heads to get more power out of it. However, I wanted to play with vintage speed. After many conversations with John I settled on trying the Shorrock. Why a Shorrock? Well because they are less common than Judson and there are hardly any on Ghias and I know of none in Australia on any VW.
If I wanted practical I could drive a Passat or Golf. It's because this is a challenge. Which I suppose agrees with your conclusion
I hope you enjoy the rest of the adventure.
Nicholas
_________________
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'65 Porsche 356C Coupe...
2005 Mecedes Benz C180 Kompressor Estate
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