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MG MGB Technical - oil from filler cap vent

I have a de-smogged 74 B with an engine rebuild (2500 miles) and a Weber. I recently changed the valve cover to an aluminum one (with a vented cap). With the original valve cover, I had noticed oil sprayed around the engine compartment and it appeared to be coming from the filler cap. A new filler cap didn't stop it. When I removed the old valve cover, oil dripped out of the hose to the vaccuum canister, and I noticed oil in the Weber (the crankcase vent is connected to the air filter). The new valve cover confirms the oil coming out of the filler cap. Please help.
Mike Melugin

With the vent system as you described it, you don't have real ventilation of the engine. I would add a vacuum fitting to the intake manifold and run a vacuum line with PCV valve to the crankcase vent (front side cover). This way the fuel vapor in the carbon canister (your car should not have a vacuum canister) will be drawn into the valve cover then through the engine into the intake manifold and burnt along with blow-by gases in the crankcase. This pollution control system added in the late 60s removed about 90% of unburned hydrocarbon emissions and is better for your engine. One of the few win-wins in the pollution control game.
Leland Bradley

Leland, you are correct. I meant to say vacu... oops. Almost did it again! Carbon canister. Would the PCV/intake manifod venting work better than direct venting to the air filter?
Mike Melugin

Mike: A couple of 'Bs ago, I was faced with your dilemma. As Leland points out, you do not have a working crankcase ventilation system. I experimented with a number of different US made PVC valves, but I could never find one that worked satisfactorily. In the end I used the Smiths PCV "Mushroom" found on the 64 to 68 engines. I used the brake booster fitting on the Pierce manifold and a short, stiff piece of hose as the base, with the stock hose connection to the front cover.
If after you have done all this and oil is still spraying out then your problem may be worn compression rings allowing blow by to over pressurize the engine.
Andrew Blackley

This thread was discussed on 09/05/2002

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