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MG TD TF 1500 - Supercharger Question

I have a moss supercharger on my TD. Attached is a photo of the top of the supercharger showing six threaded holes in a circular pattern around a center port.
Does anyone know where that center port goes and how to remove the plug?
As you can see from the picture I am using the vacuum port on the plate near this assembly but it is very small bore. If the mystery port does indeed go to the intake side of the supercharger i.e. between the vanes and the butterfly valve in the carburetor, then it would provide a larger vacuum port for me.
TIA,
Mort

Mort 50 TD

Mort just curious what do you use the vacuum line for? My supercharger from Mirage Garage does not have the port you asked about.

Joe
JWP Policastro

Mort Are you running that line from your Valve cover? I don't know that running dirty oil vapor into the blower is the best thing for it. Maybe Tom Lange can clear this up for me but I don't think I would want that oil vapor and such causing grit to grind itself through the rotors and the case. You'll be loosing boost as the tolerances open up from scores JMHO
W. A. Chasser

I think you would find the shaft for the by pass valve under that plug. I wouldn't touch it if it were me.
L E D LaVerne

Keeping this alive. Hoping Mort will answer its use.

Joe
JWP Policastro

Gentlemen,
The “plug” in question is the race shell of a needle bearing used for the supercharger bypass shaft, a feature disabled by Moss. Attempting to remove it for a source of vacuum would be a very bad idea. My question is, “what are you using your current connection for, a brake booster, PCV connection?” if so your current connect should work fine as it will only see vacuum and not positive pressure.
A Peddicord

Thanks Terry.

Joe
JWP Policastro


Joe,
My question about that particular port on top of the supercharger was answered by Terry above and you acknowledge that answer. It is not a larger volume source of vacuum as I had hoped.
Although I do not believe that I have resolve my issue yet I will keep you all posted on my progress so far. My goal is to keep the crankcase under vacuum instead of positive pressure in the hope that this will diminish some of the oil leaks . I have been testing various configurations in order to achieve this. I have tested the vacuum source from that small port on top of the supercharger. It does retain a reasonable vacuum between 15 and 25 inches of mercury constantly during operation. I have also tested the vacuum reading just below the PCV valve. At this point there is also the same vacuum. My next step was to see how this vacuum effected the larger volume in the crankcase and lower half of the engine. I placed my gage at the dipstick opening. I got zero reading on the vacuum gauge. I did however pick up about a half a pound of positive pressure during those periods. As of now my conclusion is although I have a constant source of vacuum there is inadequate flow to cause a negative pressure in the crankcase. I then hooked up a small vacuum cleaner hose to the breather pipe. I ran the vacuum while running the engine and was able to take a reading at the dipstick and maintained about 4 inches of mercury vacuum in the crankcase constantly. Obviously the greater flow provided by the vacuum created the condition that I am looking for. I do not, however have a long enough extension cord to run my vacuum cleaner while testing it on the road. I am going to take apart a 12 V car vacuum and see if I can create a greater flow under real-time operating conditions. I suspect running a vacuum cleaner motor constantly will burn it out but this is just an experiment. If it works I will get a better motor to run the vacuum device. I have a few other ideas for high-volume vacuum that I will experiment with also.
I am thinking about inserting an angled tube into my exhaust pipe and use the Venturi effect to create a vacuum. I will keep you all posted as I go along. Any ideas and suggestions would be most welcome.
Mort 50 TD

Thanks Mort

Like you I also run a newer supercharger on my TD. I was really interested because I was hoping to use a vacumn line for a different reason.

On my TR6 I have removed all the emissions stuff and I set my timing using a vacuum gauge and I have found that to be much easier and faster then a timing light and honestly a better method on that car.

In regards to the TD I thought perhaps you were using it to vent the head after you removed the standard oil bath filter. On the TR6 when you remove all the emissions stuff on the TR you have to relieve pressure at the valve cover or you do have leaks because of over pressurization. On the TD to solve that issue if there actually would have been one I put in a vent where the hose vented to the old oil filter. See picture below of TD vent.

Just in passing I have not encountered any leaks after the supercharger install. I do have a dime size or smaller drip from from the rear main area. I do not have any other leaks. Now I know I need to also add that the engine gaskets are fresh. Engine only has 1600 miles on it. Leaks will come I am sure.

Thanks again and hopefully you can see I had two reasons to be interested -- supercharger and timing.

Joe





JWP Policastro

Joe,
From your photo it looks like you have the same port but it is being used as a pressure relief valve for backfires.

I have that same feature but in a different location.
Mort

Mort 50 TD

Joe,
I am interested in the fact that you have almost no leaks. What did you do in the area of the rear seal to deal with the leak?
Mort
Mort 50 TD

Mort as you are aware there are probably three possible solutions to the rear seal oil leak issue in use - the Moss conversion kit, putting in a modern seal or using a combination of new parts, machine work and doing a lot of fitting to keep the tolerances to MGA standards in the rear seal area. Honestly all options above can work.

However, option number three requires a real partnership with a machine shop and is a expensive and time consuming option and may not be a option for everybody. IMO It also requires the most in depth knowledge and experience of these engines. When the current engine was rebuilt this option was used by the builder.

Like I said as the engine wears you can expect this area to wear and those tolerances to expand and you can expect a larger leak over time.

This winter I am going to rebuild a spare engine for this car. My first attempt will be to replicate option number three above. If I can replicate and hold the tolerance to MGA standards I will use this method. If this is not successful I will go to the Moss option. Option number two above requires permanent modification of the block and that really makes me nervous. These blocks are hard to come by. " Do no harm" seems to be the best advice.

I have access to a T expert who has been working on and rebuilding these engines and cars for over 50 years, a vintage racer who has worked on engines for years and a superb machine shop who has done many of these engines. Also this is not my first rodeo. If I did not have these backups behind me I would go with the Moss option. It seems to work if done correctly by following the directions explicitly.

Hope that helps. I never expect my old cars to be as oil tight as my modern cars. Just is not going to happen. That is why modern man invented cardboard, O'Reilly sells oil pans and I painted my garage floors and do not park my old cars in people's driveways.


JWP Policastro

This thread was discussed between 15/07/2016 and 27/07/2016

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