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MG TD TF 1500 - Eaton super charger

Would it be possible to run an Eaton supercharger anti clock vise? I.e. change inlet and outlet. Thinking of installing a front mounted Eaton supercharger.
Y Strom

It would not be advisable to run a standard rotation (clockwise) Eaton supercharger counter-clockwise. While it would move air in the opposite direction, the internal seals for the gearcase would not stand for the abuse and the air flow would be severely compromised. Some counter-clockwise Eaton based superchargers were manufactured years ago by Magnuson for Honda applications, but I understand they are not manufactured today.
A Peddicord

Thanks for your information.
As there is no suitable Eton SC for 1:1 Connection, a gear has to be incorporated. If it could have been operated CCV a belt transmission would have done the job, but a gear transmission approx. 1:1.8 will also work and give CV drive with the SC I have in mind.
Y Strom

One of the problems with using a direct crankshaft driven supercharger is the 1:1 drive ratio. Most superchargers us a belt drive for this reason, so they can spin the blower at a greater speed than the crankshaft. With the Eaton based Mirage Garage superchargers that I build, I use a 1.33:1 drive ratio. When the engine is turning 5,000 RPM, the supercharger is turning 6,650RPM. Historically, when using a direct drive 1:1 blower, you must use a much larger blower as you have less supercharger RPM to work with. The Mirage Garage blower is 750cc swept volume per revolution. At 5000RPM x 1.33 it will deliver approximately 7.5PSI (0.5Bar) To achieve this same pressure with a direct 1:1 drive, you would need a 1000cc to 1200cc blower. This Summer I had the privilege to examine a couple of the pre-war “ERA” GP cars, 1500cc engines with monster (2,000cc) crank driven superchargers. Extremely fast cars with a glorious supercharger sound.
A Peddicord

I contacted Eaton and asked that exact question and they didn't reply!

That question was directed towards the newer screw type superchargers. I wanted one for a Honda so I bought a whole car to get a complete package.

If you are after a vintage look, the Roots type blowers would be the type you want. With straight lobes and straight cut gears, there's no reason why they can't run bidirectional. If you are looking for for real boost pressure, you'd have to select a large unit as previously pointed out. You might start a search with Wieand to see what they recommend.


An Eaton blower is a “semi-axial flow, hybrid Roots supercharger”, in other words an air pump. A “screw blower” while looking similar, is a different animal, as it is a true compressor. There is no internal compression in a Roots type blower. Hence a lower outlet temp and greater efficiency. I think a Weiand 6/71 blower might be a little big for a humble 1.25L XPAG. Keep your eyes open on eBay, I’ve seen larger Marshall’s, Wade’s and Shorrocks available recently. Eaton’s front drive, rear inlet design does not lend itself well to a direct drive on a T-type, thought it might look cool with the carb pointing straight forward!
A Peddicord

Terry, I found your above responses very interesting.

Having installed one of your S/C units, purchased from Tom back in January 2014 and some 20,000 miles ago, I have often wondered how much boost is produced. With a 4.3 rear axle and 5 speed gearbox, 100 kph (62 mph) is achieved at 3200 RPM in the overdrive gear.

You state that at 5000 RPM the blower produces approximately 7.5 PSI. Using those figures, is it correct to assume that at 3200 RPM, 4.8 PSI is delivered and at 4000 RPM, 6.0 PSI?

Rob Woodfull

I recall from the days when I was running a prewar MG that superchargers from a Mercedes SLK, a MX5 or a modern Mini could be fitted to older cars.

Jan T
J Targosz

I have a friend who runs a Volumex crank blower on a couple of his MG's. One is this 37 TA with a 1500 XPEG and a Datsun 5 speed. While it looks cool I wonder about how efficient it is give the length and the volume of the plumbing involved to get the charge back to the head. I would think tunning the carb would be a pia .

L E D LaVerne

Here is 33 L type racer with a 6 cylinder.

L E D LaVerne

A lot of interesting information – most appreciated.

Currently I use an Eaton (with an internal gear + 100 %) fitted to a homemade manifold and with a split pully. By shimsing the pully I get the desired pressure. Started with 1.5 bar, but that blow the gasket after three km. Now I have shimsed it to give only 1.2 bar, approx. ratio +7 %, which is sufficient for me. See image.

Looked at the Weiland. Nice pieces, but I think they will be too long for a TD. Even the Eton I am using will be too long.

I am now looking at a very short SC 0.5 l/REV. I don´t know what type it is - probably Japanese made.. Have just seen pictures of it yet, but it looks promising. With a gear say + 60 % it will probably give enough pressure and also rotate CV. From the pics I can´t
understand why it shouldn´t be possible tu run it ACV.

As only one image per comment is allowed, I will enclose an image in an extra comment.

YS Strom

Image of Sc I am looking at.

YS Strom

It is always interesting to see the new superchargers that people come up with. If the ports are on the top and bottom of the blower, there is probably no reason why you could not use it CW or CCW. The one point you should check is the seals, most modern seals have a preference to direction of rotation due to the fact that they often incorporate an Archimedes thread in their design. Hard to tell from the photos how large this blower is, you will need 1000 to 1200cc to work effectively as a direct 1:1 drive blower. Good luck with your project!
A Peddicord

Mr Strom
I'm currently pre-occupied fitting a Moss blower to my '67 MGB but I have a Toyota SC14 tucked away for future fitment to my TC (1380cc) - the blower displacement is 1420cc. There is a smaller brother which is the SC12. They look very period and can be used either cw or ccw. A lot of T Type owners in Australia are using them.
I like Terry's product very much but also want to do my own thing with my TC.
Peter Malkin

Hi Peter, does anybody sell a locally brewed SC kit for a TC in Australia?

Rgds Trevor Burnett
t burnett

Apparently there is a chap called Gill Taylor in Victoria who has a kit.

Declan Burns

Hi Peter

Have now ordered a SC 12. I like the look and am not mainly after speed and efficiency. it is more of a challenge.

Have also ordered a 0.5 l Roots type to see if it can be fitted with a small belt gear, as I hope it can be run ACV

Hi Declan

Tried to open the link you referred to but failed??

As it will taka a long time to get the SC12 from the other side of the globe - NZ - it will take a long time before there will be anything to report.

In the mean time I will look for a suitable SU. I happen to know someone who has 9 banana boxes with SUs. I think a 1 1/2" will do.

YS Strom

The link works for me-copy it into your browser.
Declan Burns

Hi Trevor
Declan has the contact correct. I have spoken with Gil together with one of his satisfied customers and came away impressed.
Good luck with your project - your blower will polish up nicely.
Peter Malkin

You might just elect to use a 1 1/4" SU due to availability and $$$.

We have a Magnacharger with 1 1/2" SU and Marshall with 1 1/4" and can't tell any difference.

Don't bother trying to adapt a Harley Davidson carb. I tried a couple and wasted a great deal of time!

Coincidentally, at this moment, I'm high bidder on a front mount Marshall on ebay.


Interesting to learn that 1 1/2” is enough. I have recently bought two for USD 70 for both. The seller had a number of banana boxes full with SUs of all kinds.
I prefer the horizontal type from Austins, but they are rare. However, there are some with float houses that can be adjusted from 0 to 20 degrees.

For the front mounted SC I have in mind, I would be interested in a vertical carb with the inlet below. I don´t know the proper name of it. Suggestions to type and where to find one are welcome. I think I have heard that SU has even mad carbs of that configuration.

I have also promised to make a kit for a MGA and I then presume a 1 1/2” will do even for a 1500 engine.

The Marshall mentioned above was a beautiful piece.
Y Strom

Do you mean a down-draft carb? I was not aware that SU had made one. Depending on the intake configuration, I would say that a 1-1/2 would work fine - just about any H4 carb will do, as long as you have a vertical float chamber (1208 is best). Joe Curto is having them re-manufactured if you need one, and they occasionally creep through eBay.

As noted above, for a front-mounted blower you need a larger-than-normal blower. I have a couple, and would be happy to hear if anyone is interested. They are not cheap, as they are in gread demand for pre-war racecars.

Tom Lange
MGT Repair

t lange

After reading this thread, I now remember, in order to get a "vertical" float for the Marshall, I used an oxyacetylene torch to slowly twist the TD float chamber a bit. Tricky, but successful.

Did you mean to say 1 1/4" instead of 1 1/2"? The blower will pump what it pumps with either carb.

SC12 = 1.2 l/rev. Looks like a smart choice for direct drive, but hat engine is it intended for?

There have been both up- and downdraft carbs I have been informed. See encl. There are also Solex carbs with updraft that might fit the SC 12 I have in mind. I might as insted fit a SU under the hood and connect it with a hose of a fairly large minimise losses.

The SC 12 is intended for a XPAG 1250 cc.

SC:s from the period are of course lovely, but at USD 160 a piece for an Eaton in good condition with internal gear 2:1 it gives a very nice and compact installation and you get a lot for the money.

Y Strom

The S.Co.T. blower setup for MGs came with a 3/8"side draft Solex Model 35-40 FHG. I wonder if they made that long intake with a bend to fit TFs. I do like that bend so it'll pick up slightly cooler air rather than sitting over the exhaust manifold. I also intend to run the fuel line on the left side of the car to reduce fuel heat. I might just run a return line to the tank, also. This car actually came from California with a return line. I've measured air temps over the exhaust up to 250F and burned my feet on the firewall many times in the passenger (right) seat so I know it has to be awfully hot at the air filter and gas line. The front mounted blowers enjoyed cool air and intercooling before intake. They didn't even need a fuel pump!

Haven't run the Scot yet so can't say how it performs with the Solex. I'm hoping to get this installed next year but have to machine a 3 sheave pulley first.

I'd stick with the SUs with their constant-velocity slide design. I set up some Harley Daividson carbs on our supercharged 1250 TD with bad results. They had everything I wanted, butterfly choke, accelerator pump, variable idle and main jets, are compact and looked great. Our TD has an air-fuel ratio meter, so adjustment was a breeze and they ran just fine, once the car was moving, but both would bog and stall at takeoff so bad, they were impractical. I learned to appreciate the function of the constant velocity slides & diaphragms a half century ago starting out with motorcycles and now with the SUs. I installed 750 Honda carbs on a two seater Honda CRX twenty years ago and still prefer it today on our CRX convertible over fuel injection.


This thread was discussed between 03/11/2017 and 11/11/2017

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