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MG MGB Technical - Aftermarket PCV valve?

Hello All,
I have a 1968 MGB with no PCV valve, just a bolt screwed into the manifold hole where the fitting would have been.

I thought about just going to the parts store and rummaging through the PCV valve selection to find an alternate.

By any chance, has anyone done this before, as in which valve works best?

As far as the manifold hole, it's threaded, is that the way it came, or maybe some previous owner threaded it?

And lastly, and I know this is an eejit question, but which direction would I mount an aftermarket valve? Old cars that had them in the valve cover, so would the vent cover outlet on my B be the same as the valve cover in that setup?

Many thanks in advance, Dave
David Steverson

Dave. I am running a factory "Mushroom" style PCV valve on my 68GT. Costs more, but it is correct and rebuildable, something that after market valves are not. Thus, higher initial cost, but lower overall costs if one keeps the car for a number of years. Plus, we know, exactly, how the factory valve should be hooked up and what to expect from it. Not a claim we can make with an after market valve, even if it "seems to be working now".

It may be possible to find a good, used mushroom valve. The diaphragm is the only part subject to wear. I had to replace mine about three years ago. Very simple job.

Les
Les Bengtson

David, I tried an after market PCV about a year ago. It appeared to work OK without making any tuning changes but I didn't leave it on long enough for a complete evaluation. I don't recall which valve I used, I just looked through a display rack and selected one that I could adapt.

Clifton
Clifton Gordon

The PCV valve *should* be on the inlet manifold, i.e. between the inlet manifold and the engine. This reduces the high and fluctuating level of vacuum in the inlet manifold to a relatively low and constant level on the outlet of the valve, and hence in the crankcase, to give a gentle and steady ventilation flow. If the PCV valve were on the rocker cover and the inlet manifold plumbed directly to the crankcase, you would be getting 20 in. Hg. or more of vacuum in the crankcase and rocker cover. The valve would also have to have a filtered inlet or it would be sucking dirt in.
Paul Hunt 2

All sound advice. Anyone know where I can pick a second one up? No joy with EBay
David Steverson

David,

I didn't have any of the pieces at the time and couldn't find them from any of the suppliers. So I gave it the "Rube Goldberg" treatment. PCV valve from NAPA and a little creative plumbing. The valve cover is vented so no requirement to plumb it in the system. If you have the stock cover you will need to include it it your plumbing. This made up system has been working just fine for 15 years now. Make any decision on the oil line pieces?

LaVerne

LED DOWNEY

I've been running a valve for an early 70's dodge 440 for 8 years now with great success. Plumbed from the breather on the side of the block to the inlet manifold. I have a proper mushroom valve on the shelf, but this works so well and is practically invisible I don't see myself removing it anytime soon.

I picked the valve up at wally world. It comes with a 90 degree elbow on it, which pulls off and leaves a nice inline valve behind. Mount it vertically just above the breather, run the other end to the intake nipple and you should have no problems at all.
Carl Holm

LaVerne,
Hey, I forgot about your photos, my memeory still a little fuzzy after the heart surgery. I think I'll be OK on the oil line pieces. I could do a setup like yours if I had the manifold inlet fitting.

Dave
David Steverson

Heart surgery?
LED DOWNEY

Yes, I had a mitral valve repair (birth defect). It just tore one day and put me out of commission for a bit. It's something all the time!
Dave
David Steverson

Interesting David. I was born with what my mother always described as a hole in my heart. She said I stayed in the hospital a month after she went home. We are at 4800 Ft elevation and she said when they would drive into the mountains around here that I would turn blue. At age 8 I spent 3 months laying in a hospital ward bed with rheumatic fever taking 4 penicillan pills 3 times a day. I was always active, ran track, played football, baseball (state champs my sophmore year), wrestled until I got my right elbow dislocated and they broke the bones putting it back together. The doctors always heard a murmur from the heart until my late twenty's and then no more. Had my eyes checked a few years ago and she suggested that I have my cholesterol checked and sure enough it was at 280. Get to take drugs for that for the rest of my life. Had physical at 50 ( 4 years ago) and they did an EKG. Said everything was ok but that my heart "sets sideways". So the kicker here is that I've been a smoker for 35 years and have resigned myself to the fact that I will most likey have the big gripper someday and blame no one but myself. Point is I thought you were pretty nonchalant abought your condition and I like that.

LaVerne
LED DOWNEY

David,

About ten years ago I switched to an after market valve listed in the Kragen book for a 1976 2.2L Toyota pickup using this as a direct replacement for the Smiths "mushroom" item. This has worked very well and has eliminated the oil consumption through the intake manifold that can occur when the Smiths valves no longer seat properly because they are dirty or just worn out. My thinking was that the Toyota had a carbureted engine of a similar displacement to the MGB, and that these valves are functional and cheap enough to be replaced on a regular basis.

When I originally made this change I verified that crankcase depression was good with a vacuum gage plugged into the PCV scavange line

Cliff
Cliff Maddox

This thread was discussed between 28/12/2007 and 31/12/2007

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