How Do I Stop My Classic Grumbling?

stop-my-classic-grumbling

If your classic car makes a grumbling noise when warm, first make sure the carburettor mixture is correctly set. Then, try retarding the ignition timing a little at a time. Growling or vibration is sometimes symptomatic of the pistons pushing down on the crankshaft before the crank pins have gone over centre – and this ‘frustration’ is likely to be more evident in higher gears where the crank has to push harder against the inertia of the car, and is known as ‘Pinking’.

If the noise goes away, check the timing marks. If it seems to be too far retarded, a fault in the centrifugal advance mechanism may be causing it to advance the timing too much. Twist the rotor arm against the pressure of the bob-weight springs. It should turn no more than about 15° and then stop. If it can be twisted by much more than this, then it’s probably wrongly assembled.

If the engine checks out as OK, it’s possible that there’s relative movement of the main- and lay-shafts of the gearbox. This may be due to a worn bearing – or perhaps an end-nut of one of the shafts has worked loose.

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2 Responses to “How Do I Stop My Classic Grumbling?”
  1. Rod Millgate

    I have a ‘grumbling’ audible in the car which disappears if I depress the clutch. The car is a Jag Mk2 3.4 fitted with the Jaguar all synchro gearbox and overdrive. A friend has said that it could be the ‘layshaft’ which has a worn bearing. Any ideas?

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    • Customer Service

      Hi, and thanks for contacting Skill Shack with Practical Classics.

      Skill Shack works in partnership with Practical Classics Magazine, which can provide in-depth answers to your question through their ‘Ask Our Experts’ pages. If you’d like to direct your query to practicalclassicshelpline@bauermedia.co.uk our team of experts will be able to help.

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      The Skill Shack Team

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