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MG MGB Technical - zenith stromberg strikes again

This question pertains to the infamous ZS carb. It happens to be on my austin marina but I didn't think that anyone would mind as I am also a proud MGB owner.
I switched my ZS for another one that I got from a friend and realized that the breather pipe that goes from the front of the engine to the interior side of the carb was not attached properly. So I attached it and after a few minutes of letting it warm up blue smoke started to billow from the exhaust. I dismantled the carb and sure enough there was oil in the carb. It seemed to be coming from the breather pipe. So I took the pipe off and faced it toward the ground and sure enough oil was leaking from it.
This isn't supposed to happen right? I checked the oil level and it is between max and min.
Does anyone have any ideas on what is going on?
Thanks in advance,
Matt
Matthew Bennett

Yes,
Your motor has excessive blowbye. Also, it sounds like you are placing the hose directly to the intake manifold, not the air filter. If this is the case, you are pulling far more out of the engine in the wrong way. There should be a vacuum brake booster on the Marina that the big hose from the manifold goes to. The breather on the motor can either be left to vent into the atmosphere or vent into the air filter. If it has excceive blowbye, then it will foul the filter in a few thousand miles.

My Dad had a SU on his Marina GT. It was an HIF style of the same diameter as the 175 ZS that you are reffering too. Much better carburettor then any ZS ever was.
-BMC.
BMC Brian McCullough

Thanks Brian;
I just wanted to be sure that we were talking about the same hose. On page 311 of Lindsay Porter's mgb restoration manual there is a picture. The pipe that is leaking oil is number 9.
Is this the same one?
I will look through the archives for remedies for excess blow-by but any advice would be great.
Thanks again,
Matt
Matthew Bennett

I realized that the moss catalog would be a better reference to be sure we are talking about the same thing. In the spring 2003 issue on page 78 it is number 57 in the pictures or part number 367-400.
Thanks again,
Matt
Matthew Bennett

On the MGB, the front tappet cover with breather
has a steel mesh in it that is supposed to
prevent oil transfer. If the engine has excessive
blow-by, then as Brian notes, the carb will
pull in oil through the breather pipe.

But if the steel mesh is missing in the front
cover, you will have the same effect.

Check out this company for an alternative breathing
arrangement for the Z-S, and additional
explanation of blow-by problems.

http://www.mgbmga.com/tech/mgb3.htm

Unfortunately, if blow-by is excessive the cause
is worn rings which implies a full rebuild.
Ronald

This thread was discussed on 22/06/2003

MG MGB Technical index

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