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MG Midget and Sprite Technical - Shorrocks Superchargers

They look good , they sound good , but are they any good. What are peoples experiences of running a shorrock supercharger on a 1275cc. Are they any good on a 1275cc engine or are they better suited to a 948/1098. Heard mixed reviews. Any body on this forum got this setup and care to comment.
R Mcknight

from everything Ive heard they are an open money pit, and arnt worth the investment and time compared to the meager power advantage (if any), Now if we are talking about the new bmw versiion that moss has come out with,,,thats a diffeant story

Just my opinion


Plenty on this in the archives...

Anthony Cutler

On the right hand drop down menue there is a tab specifically for superchargers
Gary Lazarus


Sadly, the C75B will NOT give you the boost required to enhance the performance of the 1275 engine.... however, if it were a 948 or even a 1098, then you would notice an improvement.

Seen this on Swiftune's Dyno, the blown 1275 gave less power than normally aspirated (twin 1.5" SUs).

M T Boldry

I had toyed with the idea of running a blown 948 in the FISC series.

It's alleged that the Shorrock actually creates a lot of heat compressing the charge, thus negating some of the gain. The plan was to use a C75B to compress the air, piping it through an intercooler before forcing through a Metro Turbo carb.

I acquired most of the parts required, but decided it would be prohibitively expensive.
Dave O'Neill 2

Ran my 948 frog S/c in the 60s with Shorrocks
In winter the carb would ice. Lagged inlet with asbestos rope. If out late at night in winter had to pour hot water over carb to thaw it before starting.
Good when running right a devil when not.
Alan Anstead

Where can I find a Shorrock for my 948 now? eBay?


Shorrocks with all the A series bits are getting pretty rare; I'd say one every 2 or 3 months on ebay, and they fetch good money. You could read up and ask around to track down the few specialists who work with them, and put an order in for when one becomes available.
David (davidDOTsmithAT stonesDOTcom)

It will probably be too expensive, but I have been really hooked on the thought of a supercharger on the 948 midget I am rebuilding after a 1.2 km hill climb in August. A friend of mine has a 1935 MG PB with the original 939 cc engine and factory installed supercharger, and I beat him with only 3 seconds with my 63 MGB!



Offers, anyone? I'll probably never use it since I no longer have a running 1098. Mk2 Sprite version. All the bits are there except the optional gauge.

rob multi-sheds thomas

Rob ..Email me at ( carmadroy at yahoo dot co dot uk )please ..Interested in your Shorrocks kit .
Thanks Roy
R Mcknight

How much does something like that weigh.

Ill take it off your hands for $20


Prop, the same weight as emptying your wallet so dont worry! ;)
Arie de Best


Im pretty sure a huge stacks upon stacks of 100 dollar bills dont wiegh near as much as that thing.

Prop...I own a scanner/printer...Prop

a few years ago I have been trying the judson, it appeared to be too small for the 1275, ending only in heating up inlet air and leading to pinging.

Be very careful with forced induction, if any I would suggest a supercharger if you are a handyman. Otherwise buy a turbo unit of MG Metro....
a.o. arnold

My first A series engine was a Frogeye that I owned when I was 16. I am now 56 and in those 40 years in between of almost continual A series ownership I can not think of anything I have not tried except a supercharger..

A few years ago I decided to fit Forced induction and decided it was cheaper for me to fit a turbo. This I did and have been staggered at the performance. Each day I drive the car now (MK111 Midget) I think to myself why did I not do this 20 years ago? instead of messing with 1400 high CR engines?

Well of course we live and learn don't we.

Anyway the point of the post is to reiterate the statement by Arnold. You must be careful with forced induction, the engine must suit the inducted pressure. I now run my turbo at about 20/22 psi to achieve this I have a static CR of only 8.3 to 1 If my basic CR was any higher then I would have to reduce my boost and thus have less benefit in power.

Make sure the supercharger can supply plenty of boost, and which ever one you choose do a lot of homework on how to achieve your goal. Forced induction by either turbo or supercharger is not a simple thing to do if you are hoping to get major power gains. As Arnold points out get it wrong and it simply makes hot air and very little power.

My engine is out of the car at the moment, when I put my foot down at 80MPH the clutch gives up the ghost and slips :-) When I had my first Frogeye if it ever got to 80 MPH (downhill) I used to think it marvelous..
Robert (Bob) Midget Turbo

I have an Eaton M45 BMW-MINI supercharger for sale if anyone is interested?

Rob Armstrong

Some years ago, I had all the patterns made for C75b Supercharger installation for Spridgets, I also had a few blowers. I sold the lot to John Mead (Meacam Spridgets). I am told that John's Son still has all this lot but is 'sitting on it'. John sadly died last year, so I have no way of knowing for sure.

I raced a PB that was blown a couple of years ago, boosted to 12psi on a good day, but HELL, did it GO.....!

M T Boldry

I have run a Shorrock on my 1098 frogeye for the past 10 years - it has never missed a beat, is silent and pulls from below 1000rpm in top gear. I get an indicated 6psi boost above about 5000rpm though I have a smaller than standard supercharger pulley. Never suffered any icing or overheating issues just a bit of blue smoke on start-up. I would liken driving to having a turbine under the bonnet. Acceleration is brisk and you could drive just about everywhere in top gear. Would be hard to go back to a normally aspirated frog now. Just my tuppence worth.
SA Wood

Tuppence? I'd buy one for that!!
rob multi-sheds thomas

I was a very lucky boy. I paid 50 for a complete set-up in 1999 complete with a load of Herald manifolds and pulleys. I sold the bits I didn't need for more than I paid for the whole lot. I've spent nothing on the supercharger since apart from a couple of sets of belts, some helicoils and gasket paper. I hope I don't bump in to the bloke I bought from - I'd be unable to look him squarely in the eye.
SA Wood

If it came with Herald stuff the guy must be a Triumph owner, so dont worry, he had it comming!!! LOL
Arie de Best


SA Wood


SA Wood

And another

SA Wood

Can you measure the OD of your blower pulley and do you happen to know the static engine comp ratio and the carb specs? Might come in handy for me later! I might have a 1215cc engine coming for christmas.
rob multi-sheds thomas


Would that be an Imp pistoned 1098, I built one once and it was the smoothest A series I have come across, I put that down to the light weight of the pistons, although the crank, flywheel and damper were balanced. They ended up in a 1380 bored engine, giving 1420, and while fairly smooth it wasn't nearly as good as the 1215.
David Billington

Actually the last comment is not quite correct, in the 1420 the 1275 rods were used whereas the 1215 used lightened, balanced and polished 1098 rods.
David Billington

80mm supercharger pulley. Minor 1098 (10MAUH prefix), +060 hepolite solid skirt standard pistons, ported 12G295 head with large inlet and unleaded seats. Dunno what the compression ratio is, I have retarded the ignition a tad (just before TDC) to stop it pinking. Standard shorrock issue 1.5" H4 carb. Dunno what needle/jet are. Maniflow LCB and RC40 exhaust, mild road cam, standard clutch (waiting for it to give up then I'll fit something a bit beefier). Standard distributor. Never had it on a dyno or anything - I'm sure it's less than optimised but it runs great and I don't really care !
SA Wood

I get home on Wednesday and hope to pick up this 1215 then. It has the later 10CC Midget crank and block and is offset bored for the first Imp piston size. I wonder how this would work with one of the alloy heads. It would be nice if it didn't need pockets for the larger valves!

PS Roy. Rocker cover will go in the post on Wednesday, too.
rob multi-sheds thomas

This thread was discussed between 04/11/2009 and 15/11/2009

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