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MG MGB Technical - Gulp Valve Replacement

I'm about to reinstall the head on my 72B. While all the parts are still setting on the garage floor, I'm starting to wonder about that ole' Gulp Valve.

Most of the emission components were removed from the car before I bought it, with the exception of the Gulp Valve. Its been cleaned and it functions. And most of the other hoses are plugged off, so just the valve operates.

There is no air pump, and I'm about to replace those 4 little fittings in the head where the air tubes used to go (previous owner cut off tubes, inserted a screw upside down under the fitting and reinstalled fittings). I'm putting real plugs in.

I've seen detox kits where they replace the 4 fittings in the head and also plug off the gulp valve.

My question is: Would it make sense to simply find a PCV valve that fits the intake manifold and use a modern PCV instead of the Gulp Valve? Would I need to get really scientific about and determine the vacuum requirements, etc., or would any PCV valve that fits be fine? This would eliminate several of the plugged of hoses currently still in place.

Or is a Gulp Valve just "oh so British", that I should just use it and ignore all those unsightly little plugged off hoses, etc. on the intake manifold?

As always, thanks for the feedback.
BobA

Bob,

The gulp valve is not a pcv valve in that it does not have anything to do with crankcase ventilation.

Its purpose is to send a "gulp" of air from the air pump into the intake manifold upon deceleration to lean out the mixture.

Go ahead and remove it and plug up the hole with either a metal hole plug or a sturdy rubber stopper.
S Rechter

Ditto. If you have the hose from each carb going via a Y-pipe to the front tappet chest cover that is the crankcase ventilation.

If you have removed the charcoal canister (for which the only good reason is freeing ip some space) and its pipes there are other things you must do. The tank pipe must either vent from a filter on the end of its pipe in the engine compartment, or you must seal up the tank port and use a vented filler cap. The port on the rear of the rocker cover must have a filter fitted, or again be sealed and a vented oil filler cap fitted. It's not too important to filter the tank port, but without it could eventually get blocked and cause fuel starvation. the rocker covwer is more important - without a filter it will continually be drawing unfiltered air into the crankcase. Eventually that port could block as well (it is only very small) and that will stop the crankcase ventilation, which will allow a build-up of condensation, scummy gunge in the oil filler neck, and internal corrosion. The carb float chamber vent/overflow ports must be piped down past the engine to avoid a fire risk. There is another pipe from the charcoal canister going to an inlet manifold port, and that port must be blocked off as well.

The gulp valve isn't British at all, it was an American requirement, UK cars never had it, or any of the other emissions rubbish.
Paul Hunt 2

This is what I get for posting the question without having the car in front of me. So much for memory. I found out there was a parts swap this morning and headed to a MG repair shop to buy parts and asked around the shop for clarifications on Gulp Valve vs. a PVC valve. Apparently I don't have my car memorized yet.

As pointed out above, and as I learned this morning, the gulp valve does move air, but not crankcase air. And since I don't have an air pump on the car anymore anyway, the purpose of the gulp valve in leaning out the fuel mixture on deacceleration (and a part of the emissions process) is not really necessary.

So I'll be removing the GV and all the already plugged hoses leading to and from it. I will remove all of it and in its place tap in a brass plug.

I have not messed about with ( as messing about is reserved for boats) carbon canister on the fire wall, nor the vapor separator in the trunk. These will be left in place. But the GV is going.

BobA

Well after ready the responses above, and after talking to a local MG mechanic, I did proceed with taking the gulp valve off of the intake manifold. I plugged the intake (center hole) with a brass plug provided by a local MG shop.

As pointed out originally my 72B does not have the air pump, and I've now installed the 4 plugs into the head where the air lines used to go.

Also, the carbon canister is still in use - and yes the hose from the valve cover still goes to the canister.

However, while doing all of this I overlooked one item - the hose that comes out of the front side cover in the engine now has no where to go as it was going to the gulp valve.

Its been pointed out that the gulp valve is not the same as a crankcase ventilation system (the reason for my initial inquiry was if I could remove the gulp valve and replace it with a PCV valve - less bulk).

Now I'll be the first to admit I'm still learning on this MG, but it sure looked like the hose coming out of the front side cover on the engine and going to the gulp valve was sure letting fumes from the crankcase get cycled up the the GV and into the intake manifold.

Please tell me what I'm not seeing on this. To me it appears I've plugged off the one place where the hose from the crankcase could go.

1. Does it matter that the hose from the crankcase is going into the open air? I need to redirect it at the least.

2. Should I now plug the tube coming out of the front side cover and stop the crankcase from venting entirely?

3. Have I done something I should have left alone? If I need to reinstall the GV I'll need to drill out the brass plug in the intake manifold.

I think I need to see more B's so I can get pictures, as a picture is worth a 1000 words!

Thanks again for any assistance.

BobA
R.W. Anderson
Stillwater, MN
R.W Anderson

The hose that comes from the front side cover should never have been plumbed to the intake side of the gulp valve. If it was then your crankcase only breathed for the short period that the gulp valve was open.

The front side cover is actually the crankcase ventillation port and should be plumbed to the intake of your carb(s). You can leave it open to the atmoshpere with an in-line air filter attached however this would not be very environmentally friendly.

Do not plug up this line, your engine must breathe. If you plug this line then all of the seals and gaskets in your engine will blow out.

Please tell us what carb(s) are installed.
S Rechter

This is a photo of my 72s crankcase breather hose and how it's hooked up. I hope the photo comes through. The "Y" connection directs a hose to each carboretor from a single hose coming from the breather pipe. A picture is worth a thousand words, so I hope it comes through. PJ

[IMG]http://i58.photobucket.com/albums/g273/PJ161/MGB%20Engine/72eng3.jpg[/IMG]
P Jennings

WOW! Talk about no longer trusting anything in how things are connected on my B!!!!!

MANY MANY Thanks for clearing this up.

My "carbs" setup looks like the ones in photo from P. Jennings - except for the major alterations in my car. THANKS - no where in my manuals have I see such a good photo.

I will go outside now and compare carbs, but I don't have the "Y" connector either, just the hose that was going to the GV. (I wonder why so many MG owners that have seen my engine never commented that something was Very Wrong!)

AND - YES, the hose coming up from the crankcase went straight into the gulp valve. It now vents to open air, until I can see how I can reconnect it to where it belongs - in to the carbs. The photo implies it is a straight hookup to the carbs, without a valve. Now I wonder what is on the carbs where the hose goes?

As I manage environmental cleanups, I better figure this out - not wishing to be a source for more pollution or global warming.

Something in the back of my head was telling me there might be a pressure problem if I plugged this hose coming from the crankcase.

So AGAIN, Many Thanks for the responses and Help. Together I may be on the road again.

R.W Anderson

Latest Update:

I have Twin SU HS4 carbs on 72B.

I have not determined a location on the carbs to attach the hose from the crank case. It appears this was only possible on the SU HIF carbs. For now I have a hose directing tube towards ground until I get this resolved - so that at least the system is venting, which apparently it wasn't before.

One possible solution would be to drill out the brass plug in the center of the intake manifold, insert brass tube and attach vent hose directly to intake manifold. As I do not see at the moment how to route it through the carbs first. Would this create a problem?

The hoses from the float chambers to the "Y" to the carbon canister is intact.

Now its back outside again, to mount carbs and get this car running, hopefully!
R.W Anderson

Your float bowl tops are secured with 3 screws. Under one of these screws you should see a triangular tag with a number (e.g. AUD???). What number do you have?
Steve Buchina

AUD 2655 is the tag number on front carb float.
R.W Anderson

Attaching the vent hose directly to the intake manifold will not work, if you use a PCV valve in the line it should work.

Clifton
Clifton Gordon

The 265's didn't have the vent tubes. So, as Clifton suggests, go with a manifold mounted PCV valve tubed to your front lifter cover. Reference ebay (Rebuilt & Ready to Go - AUD135 from 1966 - 1967: Item number: 190103719273). The pictures within this posting show the setup you need.
Steve Buchina

This thread was discussed between 14/04/2007 and 17/04/2007

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