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Question about anit-gulp valve

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M

metonzed

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Newbie here....and right off the bat I need some guidance please. I am the proud owner of a 73 MGB with supposedly a rebuilt motor and carbs..well it got flooded last night and gas poured like a river out what I think is the anti-gulp valve. It ran fine before so I have no idea what is going on......help?
 
Could you describe the "anti-gulp" valve?

The only time I've had that symptom, it's been a float problem(i.e. something related to a float).
 
I think he is talking about the anti run on valve on the passenger side of the firewall. Probably filled the charcoal canister with fuel because of a carb float as mentioned. Probably just a bit of dirt or trash in the needle and seat. There should be a connector between the carbs that loop over the carbs and then goes to the canisters. Pull both ends off the carbs and have someone turn on the key(and be ready to turn it off quickly) and see which carb is flooding. If you have the original carbs they will be the HIF's. You can remove and clean the needles without removing the offending carb. Its gonna take some swearing and patience. Remove the air cleaners. Then remove the 4 posidrive screws from the bottom of the carb(they look like phillips screws). Have a container or shallow pan ready to catch the fuel that will come out. Next look for the screw on the side of the carb that is the pivot for the float. (a mirror will help figure that one out and i think it is a straight screw driver for that one).Seeing whats in there with a mirror will also help when it come to reassembly. When you pull that out have your container or tray ready to catch the needle that will drop out from above the float. Next step after disassembly is to clean the needle and seat area. I would spray carb cleaner on them and call it good. The tricky part is getting the needle (pointy side facing up) to go back in and get the float reattached. The needle will want to drop out and this can be a pain and fiddley to do. With any luck the big "O" ring on the bottom cover is ok and the bottom cover can be reattached. The bottom carb cover has a bump in it and should go on to match the one on the carb that you have not messed with. When reinstalling the air cleaners be sure the vent holes in the aluminium pieces are at the top and match the holes in the carbs. I think thats all the steps except checking for leaks. Before reinstalling the lines that go from the overflow to the canister check to see if you fixed the problem.(after turning on the key check for leaks here and at the bottom covers that have the "O" ring!) Feel free to add to this if i missed anything! Bob
 
If the last post does not make sence then you probably have non original carbs on you car and this will not work! Be sure the engine is cold and you are not smoking ! Gasoline is very dangerous (BOOM) and if it leaks onto black pavement it will make a hole in it! (also kills grass!) Bob
 
Bob, a 73 doesn't have a anti run on valve, does it? I see no way that could it be the gulp valve. Is the air pump in operation? No need for a gulp valve if it isn't. <span style="text-decoration: underline">What kind of carbs does he </span><span style="text-decoration: underline">have?</span> Sounds like a float is sticking.
 
Paul, correct. Sounds like a float is sticking. My 72 had a anti run on valve. It connects to the carbon canisters on the passenger side firewall and there are 2 wires going to it.When the floats stick it fills the canister and i THINK its leaking from there. There really is not much info to go on with the original post. That is why i reposted that if the carb repair does not make sence then he probably has had a carb change. 72 was the first year for HIF su's. With a term like "anti gulp valve" i am leaning toward the anti run on and not the gulp valve. Bob
 
Wow, thanks for the quick reply.....and I think you guys are exactly correct in diagosing my problem. I mixed up my gulps and run ons. I was trying to look at a schematic online and thats the area I looked at. I will dive in tonight and check for a stuck float with fire extingguisher in hand! I think my carbs are SU's? This is my first experience with British Royalty and so far it has been interesting to say the least....the prince of darkness has already made himself known along with this issue. What the heck, it's better than watching TV!
 
bob67bgt said:
Paul, correct. Sounds like a float is sticking. My 72 had a anti run on valve. It connects to the carbon canisters on the passenger side firewall and there are 2 wires going to it.When the floats stick it fills the canister and i THINK its leaking from there. There really is not much info to go on with the original post. That is why i reposted that if the carb repair does not make sence then he probably has had a carb change. 72 was the first year for HIF su's. With a term like "anti gulp valve" i am leaning toward the anti run on and not the gulp valve. Bob
Click to expand...

Yup, I agree with the sticky float idea.
Now, I have a 72 that's restored to factory specs and it doesn't have a run on valve.
I bought this car 25 years ago from the second owner and restored it in 2006. It's as original. Photo.
72eng2.jpg

The run on valve might have been introduced later in the year. My car was built in July. We all know the British were famous for mid year changes and using last years left over parts.
jester.gif
 
I've got a running-on valve in the '74. But, of course it's a GT, with a body designed by Pininfarina, so it's obviously superior to the Roadster. :devilgrin:

Does anyone want to fill our newest friend in on the delicacies of SU maintenance and overhaul?

Re: your engine photo - I'd say that it's better than original :smile:
 
I stand corrected! My 73 had the anti run-on and the 72 did not. Also looking at the Moss catalogue 8/72 is when the first 73 was built and that is when the valve was first used. Good catch Paul and nice engine bay! Bob
 
bob67bgt said:
I stand corrected! My 73 had the anti run-on and the 72 did not. Also looking at the Moss catalogue 8/72 is when the first 73 was built and that is when the valve was first used. Good catch Paul and nice engine bay! Bob
Click to expand...

Bob, Didn't John Twist have a video out on the run on valve? I think he suggests removing it and it's connections and trashing it as they are prone to malfunctioning in a problem like this along with flooding the canister. I wish I could remember the link to the article. I think he also said something like they have contributed to engine fires. If I had one, I'd deep 6 it. PJ
 
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