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MG MGB Technical - strange noise/feeling.

probally just being paranoid but started driving my 1976 bgt this week after a 3 wk spell off work and she seem to be a bit rough when cruising at around 50mph in overdrive. dosent happen in any other gear, only when in overdrive and foot is just resting on the pedal. car feels like its miss firing but its not/ or something rubbing.
sorry to be vague but hav'nt really had chance to investigate further.
car is an everyday drive around 15-200 miles per week and is standard/no mods rebuild engine around 15000 miles with 87000 on the clock.
jr williamson

Certainly time to investigate now, and not wait till something fails. One of the first and best pieces of advice I read when I first started MGing was 'listen to your car, it is talking to you' i.e. investigate any change in sound, feel, smell or appearance before it causes a breakdown.

You should have OD in 3rd and 4th, it is only on OD 4th or OD 3rd as well? Because OD 4th is the 'tallest' gear it puts the greatest stress on the engine when accelerating, so any load induced misfire is more likely to happen in that gear than others. But if it is only happening at a steady cruise and not accelerating, not only does it tend to discount a load-induced problem but it should also happen in other gears *at the same rpms*, i.e. not necessarily the same road speed if it is an engine speed related problem. If something is rubbing with the wheels and transmission then it should continue to do so at a given speed in any gear, or even if it is knocked out of gear and the engine is idling, or even if the engine itself is switched off and stopped. If something is rubbing around the engine then again it should do so in any gear, and in fact be more audible (at least) in lower gears i.e. slower road speed and less wind noise.

More diagnosis and info required.
Paul Hunt

Any unbalance in the carbs is most evident at very light throttle openings. It's also possible that the points have corroded a bit with standing. I would clean the points and top up the carb dash pots then retune the carbs and see if showing your car you really do love it solves the problem.
Stan Best

This thread was discussed on 08/01/2009

MG MGB Technical index

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