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MG MGB Technical - oil leakage from engine breather system

Went out with the wife for a nice summer drive this evening and she noticed oil drippage through the garage and out on the street when we got back. I checked and it was definitely oil. The drips were about every six inches and probably went back over the entire 20 miles that I drove tonight.

When the engine cooled down I did some investigation and found that oil was dripping pretty regularly out of the side chest breather pipe attached to the engine. this is an open pipe found on the early 63-64 mgb engines. As the engine cooled down I bet I had about a two inch wide oil spot on the floor underneath. I have noticed this before after a long drive.

Some background - The current engine is an 18GH series (5-main bearing) that has just been rebuilt with 1950cc pistons, kent cam, and leadfree head. The engine currently has about 600 miles on it and is still pretty tight. I put the original breather tube from my old 3-bearing (18g) engine on this new engine as the block I bought did not have the breather assembly with it. I am also running an alloy rocker cover (no vent) but with a vented oil cap. this hole is open as i checked it tonight so it is pulling air through it.

I checked through some of my service and parts manuals and found that the 18gh engines have a direct brething hose from the side breathing vent to the carburators. mine currently vents into the air and on the gournd evidently.

does anyone have any experience with the early model engines so they can advise me on how best the engine should breath.

Thanks for any advice or links to websites.
edward

Edward,

Early MGs (MGAs, Magnettes, MGBs) which used the draft tube you described ALL also used a vapor hose running from the valve cover into the aircleaner to help minimize crankcase pressure, especially at low roadspeed. In theory, at higher roadspeeds the draft tube is intended to suck crankcase gasses into the passing slipstream, but at low speed or stationary it is nothing more than a vent. Certainly you could add this missing breather hose. Also you could replace the draft tube by adding a PCV system to your engine with either a stock Smiths valve or comparable part.

Cliff
Cliff Maddox

The early side chest breather (the one that looks
like a can that is welded onto the end of a pipe)
should be stuffed with a metal mesh to catch
the oil fog from exiting the crankcase. Early
midgets and Sprites used this type of breather
arraignment, also.

This mesh sometimes accumulates dirt and old
oil and is often removed during engine rebuilds.

If the breather can is empty, it can be re-stuffed
using one of those all-metal kitchen pot scrubbing
pads. Do NOT use steel wool or metal shavings!!!

Sometimes during a long run, oil can accumulate
in the breather can and be "gargled" about and burped out onto the road. Many race track techs
show much displeasure in this - and an old road
racer mod for further reducing exiting breather oil
is to braze a 3/8" hose fitting barb on the bottom of
the breather can, and a 3/8" hose fitting barb on the
side of the oil pan. Attach a steel braided hose
between the two (avoid the exhaust header). Now,
excess oil finding it's way into the breather can will
get caught by the metal mesh, and then drip down
into the hose and run back directly into the oil pan.
This isn't 100%, but it helps greatly to reduce the
breather oil that would otherwise drip back out
into the tappet chest and wind it's way back into
the breather can again, and again.

I'm with Cliff in that you should try to arraign the
breathing system so that it utilizes some sort
of PVC going to the carbs or the manifold, or,
at the very least, a breather hose should be
routed into the air cleaner can(s).
Daniel Wong

This thread was discussed on 26/08/2003

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