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MG Car Repair/vented gas smell



carb port
carb port  

I received the canister and it has a hose port at the side of the bottom. And three ports on top without any labeling.I'm a little confused on the instructions on connecting it up. There is a hose coming off the webercarb and going to the breather pipe. I can put a Y connecter in there and the other hose of the Y can go to the valve cover pipe. But I don't have or see where that is. Will sent pic's on motor cover and a port in the back of cover the is plug closed(maybe that's it). My vacuum is pointing away from my distributor and not sure what you mean to connect it the mounting flange of the carb.The one hose on the carb is going to the breather hose. I found a picture of my weber carb online.  It look like my carb port has a screw put into it.  It would be really hard to get a hose on it and hope that it would not have a kink in it. There is only about an inch of space before the valve cover. Also I have been told that I have an alison/crane electronic ignition system.

again thanks a lot

Hi Al,

I can't tell from your photos where those pipe fittings go to. But the carburetor port is easy to test. On the port on the carb, put a vacuum gauge on the port and start the engine and warm it up and then let it idle. with a warmed up engine and a low idle if you see little to no vacuum, and when you open the throttle and increase RPM you see vacuum and as you increase RPM up high the vacuum lowers (but not below 5 in hg)
If that is what you have then the port is a "Ported vacuum" and it must go to your vacuum advance unit on the distributor. If however you have a Vacuum Retard unit on your distributor, you can NOT use that carb port for the distributor. If it is a vacuum retard unit on the dist then that must be connected to straight intake manifold vacuum.

If you are nt sure if it is a "Retard" or an "Advance" unit on the dist. Look at the port on the vacuum unit. If it points away from the vacuum unit and away from the dist, then it is a "Vacuum Advance" unit. If however the vacuum port is mounted on the distributor side of the unit it is a "Retard" unit and must have straight vacuum.

Where does that block off hose at the end of the head go to?

Most Weber carbs I have seen installed on British cars had only one port on the air filter. But the MG usually have two breather hoses. One from the valve cover and one form the lifter side covers. Both these need to be connected to a "Y" pipe and on to the one port on the air filter.

The charcoal canister was used over the years in several different ways. Some cars had two canisters side by side.

Generally the two out side ports on the top are for the gas tank vent and the carburetor float chamber vent. The center one on top was called a "Purge" vent and went to the engine valve cover. If your engine does not have a lot of "ring blow by", I would connect the engine side cover pipe to the carb air filter and the valve cover pipe to the center port on top of the canister. Then connect the fuel tank vent to either one of the top side ports on the canister.
If you have a float chamber vent port on the carburetor, connect that to the other side port on the top of the canister.

I notice in your photo that you have an aftermarket valve cover. Does it have a vent port on it?

If you want to just look carefully at the engine side covers to see if the front one has a port on it and if the valve cover has a port on it and give me the numbers off of the Weber and I will see if I have any data on a float chamber vent on it. Then I can draw you a hose diagram that will come close to meeting emissions.


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Howard M. Fitzcharles III


MG from 1956 (USA versions only) up and Engine theory.


Dealership line mechanic on MG, Triumph, Jaguar for 15 years, Instructor in commercial mechanics school 2 yr. Product information manager for piston and valve manufacture, Instructor & hotline answer man for import car parts importer 15 yrs.

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Import Car magazine

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