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MG MGB Technical - 74 GT HIF4 Carbs

Another question to test the knowledge of MG enthusiasts. I have a 74 GT with carb problems,before i got it, it was sitting in an underground carpark for 2 1/2 years. I have been trying to tune the carbs but they are overflowing petrol into engine bay and flooding engine. Any suggestions.
G Thompson

Glenroy;; They will need a good internal cleaning. Most likely a new set of float valves.
Sandy Sanders

First try running the engine with the fuel pump disconnected which will empty the float chambers, then reconnect the fuel pump. The resultant rush of fuel through the now wide-open float valves (normally they only open a smidgen) often cleans out any debris. But after standing 2 1/2 years the float valves could well be past it. Also check the floats carefully, one may have a leak and be full of petrol. Unless you know the condition of the car when it was abandoned any number of things could be wrong.
Paul Hunt 2

Oh, with HIFs this entails removal from the engine and removal of the bottom cover, which will entail replacement of the gasket or you will probably get leaks on refiting.
Paul Hunt 2

Thanks for all the info, Paul i did give the carbs a good clean when i first got the car. It was running then but miss firing badly.
G Thompson

Forgot to mention, carbs are fitted with K + N filters.
G Thompson

Another cause of SU carbs flooding the engine is if the vent tube is blocked. This prevents the float rising and shutting off the fuel, so fuel is pumped up the jet and straight into the inlet manifold. If the vent pipes are clear, and indeed if fuel is flooding out of them when the ignition is on but the engine is not running, then the float valves are not closing, either because they are stuck, dirty, or the float has sunk.

K&N filters (or any other filters) will have no effect in this respect.
Paul Hunt 2

This thread was discussed on 25/11/2005

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