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MG MGA - Crankcase vent pipe

The vent pipe from my front tappet cover is oriented upwards and forwards. Ihis takes it very close to the exhaust manifold, about 1/4". I don't have the tailpipe, I will fab it from copper, but should the stub from the cover not be angled to the rear? My block is Austin A60, not MGA so I am uncertain of the origin of the cover plate.
Art Pearse

Art,

Image is attached from the MGA 1600 factory Service Parts List.


Mick

M F Anderson

Art,

Would the front cover fit on the rear opening?
If so, is that any improvement?


Mick
M F Anderson

Art

If by forward and upward you mean one like this (see image), you have an MGB tappet cover. The MGB then had a rubber pipe attached to it.

Steve

Steve Gyles

The moss catalogue shows the MGB vent as Steve mentioned. Is this what you have? Or something else?

See Moss image attached, items 6 and 15.


Mick

M F Anderson

Mick, mine is not like yours, See pics. I thought about putting it on the rear, but it comes too close to the centre exhaust branch. I think I will have to move it to a vertical position. Steve, it is also not MGB type
Art Pearse

Here are the pics.


Art Pearse

Another

Art Pearse

I wanted to upload a 3rd pic but there is a glitsch somewhere!
Art Pearse

Art
It needs some text in the comment window otherwise the picture just won't appear.

Your tappet cover is standard. The so-called J pipe is close to the exhaust, but as it's rigid, the two never come into contact.

The J pipe should fix at the lower end to the front bolt of the blanking plate for the fuel pump (that's the pentagon shape underneath the tappet covers)
dominic clancy

Dominic,

The factory Service Parts List shows the pipe on the tappet cover sloping to the rear, not forward like Art's item. It also is supported at the rear bolt of the mechanical fuel pump blanking plate.
Photos in the Workshop Manual and many other books confirm this setup.
SPL image attached.


Mick

M F Anderson

Art,

Maybe in a million to one chance you have rear cover from a mga twin cam, upside down.

See image from Twin Cam SPL.

Then again maybe it is off an Austin A60 as is the rest of your engine.
Anybody got an Austin A60 to confirm?


Mick

M F Anderson

Wouldn't it be simpler to get hold of the right one? There must be thousands of them kicking around, I'm sure someone has got a spare.
Lindsay Sampford

You are probably right Lindsay. However it probably is an A60 plate, but it would be nice to solve the mystery. I posted it on the Farina board. Meanwhile I am going to attempt a rotation - try unsoldering first, if that doesn't work, cut and re-weld. If I screw up, as you say, plenty of others out there.
Art Pearse

Fixed the problem. Cut off the pipe with Dremel disc, leaving short stubs. Used a sleeve cut from a 1/2" copper tube elbow which fits exactly, and soldered it back, this time with the front plate rotated 180 so the vent pipe is at the rear of the plate, angled 45 to the front. Flex copper 1/2" does the rest. I'm OK as long as the tappet cover is cooler than 183 deg C!
Art Pearse

Nifty idea Art! I could see the copper elbow "waiting in the wings" in one of your pictures and was wondering how you were going to use it!
Lindsay Sampford

Here is the final result


Art Pearse

I hope you have chamfered the bottom off at 45' to promote the suction effect from forward motion from the car

David
David swaine

Attached is part of the engine drawing from the A55/A60 workshop manual.

Definitely A60 I would say.

Malcolm

Malcolm Asquith

David - have not, but will do!
Thanks
Art Pearse

What is the proper way to route an MGB breather mounted in an MGA engine bay ? Here is a photo of my set up so far
http://picasaweb.google.com/chrisvelardi/MGARebuild#5356674272054851906
Chris Velardi

Chris

I cannot access your photos from work. However, I went through a not dissimilar discussion a couple of years ago. Whilst a full MGB breather system may be an option for you, my hybrid version was 'torn apart' by Barney. I eventually heeded his advice and retro-fitted the full MGA system on my 1800. I will happily admit that the engine now runs a lot cleaner than it was doing then. Gone are the sludge and fumes. The full story is in the archives, complete with Barney's dissertation on the subject.

Cheers

Steve
Steve Gyles

Chris

This was the archive which Barney used to explain all about MGA crankase ventilation: http://www2.mgcars.org.uk/cgi-bin/gen5?runprog=mgbbs&access=&mode=archiveth&subject=6&subjectar=6&thread=200612281420095446

You will see that I went from being very argumentative, to conciliatory, to acceptance, to happiness. Car has been running very well on breathing matters ever since.

Cheers

Steve
Steve Gyles

I figure the suction is 1.25 ins water at 50 mph and 2.8 ins at 75 mph. Quite a bit.
Art Pearse

Impressive, Art. Where did you get the numbers?
Barney Gaylord

Barney, it's Bernouli again. The pressure change is equal to the kinetic energy per unit mass of the flowing air. This is 1/2 x density x velocity^2. So air at 1.2 kg/m3 and V = 33.5 m/s (75 mph) gives 673 Pascals or 2.7 inches wc. Same formula as for a pitot tube measuring airspeed.
Art Pearse

I hate to spoil your fun, Art, but calculations won't match the real world inside the crankcase with an open vent on top and some blow-by from the piston rings. Your numbers may be valid for vacuum directly at the outlet end of the pipe, and even that is impressive. I know the draft pipe does move a lot of air through the crankcase at road speed.
Barney Gaylord

Is there some confusion over inches of water vs. inches of mercury? Arts figures seem high but they are in inches of water. Inches of mercury, the more conventional measurement (at least when speaking of engine vacuum) is quite less. Ratio of inches of water to inches of mercury is roughly 14 to 1.
James Johanski

The calculated figures of course relate to the depression at the tip of the pipe, relative to the outside air, and I only did it for curiosity as to the magnitude of the effect. The actual flowrate of air induced at the top end (via the filter and the valve cover) depends on the geometry of the pipes involved and the competing blow-by gas. In ins Hg the figure is 0.20. As a comparison, most home furnace fans generate only about 0.5 ins water, but move a lot of air.
Art Pearse

This thread was discussed between 07/07/2009 and 19/07/2009

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