MGB running on

Jul 04, 2006 3 Replies
K

Does anyone here have a cure for 'run-on' in a ' 70 B? Virtually every MGB I've ever encountered seems to run on after being switched off to some extent, particularly when warm. On well-used engines I wrote it off to a build-up of carbon in the combustion chambers, on valves, pistons etc. but my engine is freshly rebuilt, .040" oversize 9 to 1 pistons, half race cam, lightened flywheel, new carbs etc. etc. It runs and pulls very well, starts easily, gets good mileage, but when I shut off it gives a couple of coughs and a shudder before it dies.



I've tried playing with the timing and carburetion but nothing seems to make any difference.



Any help would be greatfully received.



Thanks in advance. KH Canada.


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A

My '72 B used to run on for 10 seconds or more - stamping on the accelerator would stop it.

I think I read that BL experimented with a diesel version of the B-series block. Wonder what gave them the idea?

Al

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K

In my case, a shot of throttle just encourages the bugger. I have replaced the leaky old SUs with a pair of 42mm Mikuni flat-slides. They have accelerator pumps on 'em, so a dab on the throttle provides a quick squirt directly into the throats, feeding the antics rather than stopping them.

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G

this was always a problem on b series twin carb engines,some marina tc models had an anti-run on valve fitted by the factory. we used to buy the kit from the main dealers and have fitted them on loads of problem cars.the anti-run on valve was fitted into the servo line on a tee piece, an electrical solenoid controlled by ignition feed, opened when the engine was turned off thus allowing cold air into the engine to stop the dieseling effect.this will stop the problem but finding the parts today will be a new challenge.best of luck mick grant

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