MGB & GT Forum

After reading this article I tried it out and mine was LITERALLY FULL of all kinds of gunk and carbon and crap!! I doubt it was able to vent at all, leading to increased crankcase pressure and thus oil loss through various gaskets and even the oil filler cap during driving. It doesn't leak when sitting or smoke aside from startup, so this could be the solution.

I just removed mine, cut it open with a dremel and pried all the steel wool filter out. You can then replace it with a basic copper pot scrubber (the article recommends Chore Boy, but I just used a dollar store scrubber). Huge improvement!

I forgot to take a lot of pictures but here's what I do have, you can see all the crud that was in mine.

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Jay D
"Bee Sting"
'77 MGB Mk. IV 1800CC
Weber 32/36 DGV Carb
Ported Intake
Pertronix Distributor
Early 70's exhaust manifold
Magnaflow muffler
Driven daily and loved daily
by a poor college student

And yes, the clock works.

Food for thoughts, it is something I will look during the next spring on mine, thanks.

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1977 MGB Red 'Victoria' and 2018 Jaguar XE 'Meghan'
All Classics:
Married, 2 children, MG MGB May to December, Jaguar the rest of the year.

where is that filter located on the engine?

The front tappet cover.

It's under the exhaust manifold on the side of the engine. There is a tube that sticks up from it.

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Jay D
"Bee Sting"
'77 MGB Mk. IV 1800CC
Weber 32/36 DGV Carb
Ported Intake
Pertronix Distributor
Early 70's exhaust manifold
Magnaflow muffler
Driven daily and loved daily
by a poor college student

And yes, the clock works.

Would it be acceptable practice to take that cover off, clean out all the crap, and then run one of those little cone shaped external crankcase breathers?

You can also burn out the tappet cover, then flush and blow to get the carbon out. Once it is clean, you don't need the little filter; hook it back up.



Edited 1 time(s). Last edit at 2014-07-29 09:13 PM by chris.

I posted this article a few days ago because I am having a lot of oil blow out of that breather pipe and I am going to try this remedy this weekend. I'm hoping it fixes it like yours!

There should be a sticky with common problems that have unusual causes... and how to fix them.



That is something that a lot of people do, however there are better ways to deal with crankcase pressure. I would read about the PCV/Breathing systems that MGBs used over the years and choose one that fits your needs. Remember though, PCV valves are calibrated to a specific engine and they will not work on different engines. There are other crankcase ventilation systems that don't use a calibrated PCV valve.

Implementing a PCV system will give your engine more longevity and keep your oil from being contaminated, as well as keeping a lot of oil vapor from coating your engine bay! It also doesn't reduce power output.

Moss motors has some videos on MGB PCV systems on Youtube, I suggest you look them up.

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1980 MGB Limited Edition (Car No. 2744)
"If anything's gonna happen it's gonna happen out there!"

Right, I am well aware of the importance of proper venting.

A previous owner removed every single bit of emissions equipment on our 73. I have installed two of those small breathers, one on the valve cover spigot, the other on the tappet cover spigot. I also replaced the oil filler cap that was in bad condition. The PO just ran two rubber houses down to the ground. My intentions are to mainly just reduce excessive blowby, keep my oil in the engine, and keep my oil cleaner for longer.

Blow by is caused by engine bore/piston ring wear and no amount of tinkering with breathers or PCVs can possibly cure that.

It's very simple to check if the breather in question is blocked or not, blow down it !

Frank!y a blocked tappet cover breather is more likely to be the result of excessive blowby than it's cause.

It was very blocked.

And wouldn't blowby be evidenced by bad compression? My compression numbers all read normal.

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Jay D
"Bee Sting"
'77 MGB Mk. IV 1800CC
Weber 32/36 DGV Carb
Ported Intake
Pertronix Distributor
Early 70's exhaust manifold
Magnaflow muffler
Driven daily and loved daily
by a poor college student

And yes, the clock works.

Not necessarily.

Even in a brand new engine the piston rings do not provide a perfect air tight seal in the bores so there will always be blowby to one degree or another, it's the principal reason why the crankcase needs to breathe.

Higher compressions can result in more blowby rather than less.

For many years engine breathers were nothing more than a pipe venting to atmosphere, usually just down to the road, it's only increases in environmental pressures which have seen closed systems introduced the strictness dictating the actual measures required - hence the charcoal filters etc. found on US cars.

This is interesting, my 77 B pushes a little oil from the filler cap and I have never thought to look at the PCV system or if it even has one. My 77 looks to have a 74 motor with no emmissions on it and twin SUs. What is interesting is that this is the second PCV issue / story this week. It seem that a gunky PCV system may be the cause of high oil usage in my 2005 Mazda 3 with 75K on it. It's a common topic on the Mazda forums.

You can also set up an oil catch can system that captures the oil but lets the gasses pass through to the ports on the carbs. Of course then you will periodically have to empty the can.

I have new cover seals in my order on its way from VB. I will be replacing the the very rusty front part of my exhaust (replaced the middle part a few weeks ago) and I am operating on the assumption that a bolt will break and I will have to pull the manifold to fix it, so I might as well take advantage and clean out the filter/trap.

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Endeavor to Persevere

"The problem with quotes on the Internet is that you never know if they're true" - Abraham Lincoln

Yeah after doing this I don't have anymore oil spray out of my filler cap so you oughta give it a try.

The only issue I'm having now is that a have a slight oil leak from the brand new gasket on this breather. Typical.

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Jay D
"Bee Sting"
'77 MGB Mk. IV 1800CC
Weber 32/36 DGV Carb
Ported Intake
Pertronix Distributor
Early 70's exhaust manifold
Magnaflow muffler
Driven daily and loved daily
by a poor college student

And yes, the clock works.