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MG TD TF 1500 - OT - Info on Marshall J 75 Blower

The attached was sent to me via Ttalk. Can anybody help?
***
Looking for assistance; hope you can help.

I recently purchased a 1948 MG TC with a Marshall J 75 supercharger. It runs great and has given me no problems……but I have been unable to obtain much meaning full information as to its operation and required maintenance from the Internet.

Do you know of someone that would have an owners manual for sale of posted the information on-line?

I am prepared to pay if I can get “good stuff””
***

Bud
Bud Krueger

I think this would be a good start.

http://www.mg-tabc.org/supercharger/index.htm
L E D LaVerne

Or here:
http://www.mg-cars.org.uk/mgtd/mgtd_accessories_superchargers.htm

Gene Gillam

I've passed them on. Thanks. Bud
Bud Krueger

http://www.flightglobal.com/pdfarchive/view/1945/1945%20-%201177.html
Marshall nordac blower for cabin pressure c. 1938
Len Fanelli

Google marshall nordec blower.
7th entry
Len Fanelli

Got one, and may convert our Magnacharger to the drip oiler, like Marshall. I'm constantly adding oil to that later model Eaton.

I rebuilt my Marshall, twice over, and regret it. It worked perfectly, but seemed to be sucking the oil into the engine and generating a little blue smoke. Ironically, the Shorrock is a total loss oil system and expects to run the oil into the engine, creating a little blue smoke, so it's not the end of the world if smoke shows up.

The original Marshall leather seals are superior to the only conventional oil seal available. I should have soaked the blower with neatfoot oil, and flipped it over and over, like I'm doing to a S.Co.T unit now.

If it isn't pouring oil in and blowing blue clouds out the tail pipe, just keep and eye on the sightglass for good drip. Let the boost gauge confirm perfect function with 4, 5, 6 psi boost!
JIM NORTHRUP SR

Jim
I have been using and racing my TF with a Marshall 75 since 1980, I still race it.

We have rebuilt it twice with new seals over that time and find no oiling problems occur until the seals go.

I use CR or SKF brand seal #11740 and CR #8782

The recommended oil feed is 6 drips per minute, I have a friend who sets his to 1 drop every 7 seconds, set this at idle speed.

Hope this helps.
Rod Brayshaw

I've sent him a link to this thread. Thanks folks. Bud
Bud Krueger

Rod and all,
I have a hydraulics business. When I first started playing with our Marshall, there didn't seem to be oil draining, as if it all sucked into the engine, but it ran well and cranked up a good boost. All logic said it was time to replace the seals. SKF bought CR/Chicago Rawhide, so there is only 1 seal available for the blower. These are conventional oil seals with a thin urethane lip seal and fine spring, designed to seal pressure in one direction only. The old seals were heavy leather that hugged the shaft and effictively sealed in both directions, as long as they weren't dried out rock hard. If I'd soaked the blower with neatsfoot oil and just run it, it would probably last forever, like "leave a sleeping dog lie."
I recall installing the new seals onto virgin bushing (or shaft?) surface, but then redoing the whole project installing redisleeves, just because... The sleeves made reassembly much trickier, as I recollect, because they could've ruined the seals, rolling the lips backwards. Anywho, it is all back together , functional and looking as pretty as you please!
I found you can set the drip to whatever you want, just don't expect to see a drip the next time you pop the bonnet. On the other hand, it is no worse than out Eaton/Magnacharger- I can pump in a slug of oil where it runs out the drain plug, but a month later, I can pull the plug and nothing comes out. I did discover that the Marhall system will circulate more oil, because I can remove the drain and let it idle for a bit, and no oil runs out; shut the engine off, and it'll stops circulating and then comes running out, the Magnacharger never has enough oi to come running out in excess.These Roots type blowers do not need a great deal of oil, but it is nice to know there is some lubing the gears, seals & bearings.
Bottom line- I prefer the old leathers seals of the Marshall and the rude & crude lubrication system that just might add a touch of oil once and a while.



JIM NORTHRUP SR

About ten years ago my MKII came with a marshall in a box, nasty looking thing. After I restored the TD and ran it for a year or so, I rebuilt the Marshall. New bearings, spacers, seals, and gaskets. Been running it ever since. Other than replacing all the gaskets last year using a good sealer this time, it's been trouble free.

Marvin Stuart

Marvin, my experience with a Marshall is exactly the same as you described. Never a problem but I have a question for you. It seems noisy when running. Due to its design and the fact that all the internal parts were new, I often wonder why it makes any noise. I know the rotors do not hit each other and oil supply is adequate which might be the first thoughts. Does yours make some noise when running?

Jim Merz

Hello, Jim. If you mean like a wild banshee, screaming noisily on a load, like going up a grade, yes , mine does that. Didn't know what it was till I met a J2 owner at a GOF, said something like "that's the Marshall screaming". Tho it does give out a bumpity or thumpity sound on occasion, haven't worried about it since. It is a beautiful piece of vintage machinery and certainly compliments the TD. Marvin
Marvin Stuart

Thanks for the feedback Marvin. Mine does give out a little clankety sound when idling. I know that the gears are in synch and that the rotors are not touching each other so I don't worry about it. I am not sure what it might sound like to others when I am at speed on the road.
Jim Merz

This thread was discussed between 05/10/2013 and 08/10/2013

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