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MGB Weber problems on MGB

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bluemg

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I have a weber down draft on my MGB, works great, but have always had a gas smell when I shut the car off and put it in the garage. I have been blaming the gas tank line and evaporation canister. Yesterday I took the air filter off and looked down the weber to find raw gas over top of the secondary butterfly
and raw gas at the bottom of the intake manifold at the primary side. Car has a standard SU fuel pump, no regulator.
I would assume I have a sticking needle valve, however Im looking for suggestions what to look for?
Thanks
 
Early Cannon manifold, I'll wager. If so, that is a common occurance: gas pools under the carb and usually makes for a hard start after the thing is warmed up, too. You could try changing the float needle/seat and adjust float height but from my experience it is a design issue with the manifold.

This is the later style, you can see a "sorta-kinda" fix in the base.
 
Yes that manifold is different, mine is more square shaped under the carb barrels
where the photo has a rounded appearance. I'm kind of thinking about going back to the SU's.
Thanks
 
bluemg said:
I'm kind of thinking about going back to the SU's
Click to expand...

:thumbsup:

The only real Weber conversion is the DCOE one. But that puts a sharp pain inna wallet. :shocked:
 
I had a 32/36 on the 79 I had. Was on it when I bought it and could never get the hesitation out of it when accelerating from a full stop. Got tired of trying to doctor it up and went to a pair of SUs. Problem not only went away, but the performance level came up considerably. PJ
 
I had same problem on my 75 Spitfire. I filed small notches in the butterflys. Got info from one of the many Weber books I accumulated trying to tune it to my car. Message me if you are still struggling. Maybe I can find it again. I'm sure I still have it all. It was a long time ago for me. But I really got into the whole proccess. It was well worth it in the end.
 
My 71 came with a PO installed Weber 32/36. Its main problem is the boiling out of the gasoline when shut down. (That is your smell). It boils out into the manifold making it too rich for a hot start combined with an empty float bowl. This is also helped by the volatile Ethanol in the gasoline, thank you EPA (and they wasnt to raise it to 15%!) . Takes a while to get it running again. Also has the hesitation on acceleration. I put a heat blanket on the exhaust manifold and it helped only a bit. The intake manifold bottom is only about 1/4 inch from the center pipe of the exhaust manifold.

The final solution was to get a pair of SU HS-4's, heatshield and manifold from the internet, rebuilt them and dumped the Weber. Runs smoothly now, starts easier cold or hot. I'm happy and the car is happy.
 
The 79 I had must have had a similar problem in the past with the PO as it had what looked like a hard piece of asbestos cut as a gasket, but was large enough to extend out far enough to shield the bottom of the carburetor from heat. Looked kinda weird, but I guess it worked as I never had a boiling problem, it was just the hesitation that was annoying. PJ
 
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