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MG MGB Technical - Weber 36/32 Slight misfire

Second time out last night in my 78B it felt great to top things off on the way back one of the neighborhood kids shouted "nice car"! ahh the only car you would get that remark in. Anyway from my last post (no one responded to) there was a slight miss at high rpms the rpms would jump between 2500-3000 rpm. Yesterday I cleaned the air filter with left over K&N cleaner and oil also cleaned the throttle plates and inside the weber. Wow did this make a big difference but the still a very slight miss.

Searching the form archives I have read some negative and positive reviews on the weber (mostly negative). The problem I am having is on a load example, at low speed in third gear there is a miss low speed in fourth there is a miss. I know you are not suppose to labor the engine in gear but living in VA beach this is sometimes impossible. Other than that the weber holds idle and has power! More so than my 74 midget I was able to pass the slow pokes with ease.

My B has a exhaust leak between the flange and manifold that could affect the running condition. The gas in the tank was a couple of years old add fresh gas. Full tune up was done, P.O. gave up on maintenance long ago. So should I be worried?

James
James D

I don't own a Weber so I can't comment on it. First thing I would check would be everything else before getting into the carburetor.

Start with the ignition system, plugs, wires, timing,etc. Webers usually like 20 degrees timing advance. No more no less. Make sure the vacuum advance and centrifugal advance are working.

Then check the valve clearances.

Check for vacuum leaks starting at the manifold gasket and the carb gasket. Webers are really sensitive to vacuum leaks as they run rather lean at low speeds.

Check your fuel filter. You may have to clean the fuel side of the Weber. They don't like dirt. As a last resort you may have to rebuild the carb...things like fuel pump diaphragm, gaskets, needle valve etc. The kits are not very expensive and it isn't too hard from what I hear. Check the archives and internet on this.
Robert McCoy

You may be encountering a slight advance and then retard of the vacumn advance assembly. This can come into play when the throttle shaft just exposes the vacumn port running to the distributor and causes a timing advance/retard pulsation. RAY
RAY

This thread was discussed between 04/04/2009 and 05/04/2009

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