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MG MGB Technical - Car stalls after highway driving

My 74B with new HIF carbs and pertronix ignition shows an unusual problem on highway driving - when I approach an exit and dis-engage the engine quickly to downshift (step on the clutch) from 3000 rpm or above, the engine rpms drop all the way to below 500 and the engine stalls. However, after around town driving, doing the same drops the revs to 800-1000, or normal idle speed, and the engine does not stall. Also, the exhaust smell rich at idle, but seems OK after hi-speed driving - no black soot on plugs. Any suggestions as to what's happening? Thanks in advance.
Willie L.

My front HS4 had similar symptoms. It turned out that the piston was binding and would not drop to its normal position right away, but would in a few minutes --- permitting a restart and making troubleshooting impossible.

The hanging got worse. The engine would fire if carb cleaner were sprayed into the filter. Once the problem was identified, no way was found to correct the binding and I ended by installing my spare carbs.
Dan

I've been told that this is a symptom of low fuel float level. However, I've never verified it myself.
Matt Kulka

I'm with Matt. The first thing thatb I would check would be the float level.

Next, I would check the fuel pump.
Steve Lipofsky

This thread was discussed between 26/10/2003 and 27/10/2003

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