How do I stop pinking?

QMy Solara pinks when going up hills or running at high speed on motorways. If I back the timing off until it stops, the car is slow and lifeless. What can I do about this? Grant Smith, Beaumaris

AFirst, make sure the correct spark plugs are fitted, as too hot a grade will cause pre-ignition. Next, check the valve clearances are correct. Clearances that are too small will upset the running of the engine – and if the exhaust valves don’t fully close, they can’t pass their heat on to the cylinderhead. They become too hot, also provoking pre-ignition.

Move on to the distributor. Examine the bob weights and springs of the centrifugal advance mechanism. Make sure they’re in good order and free to move. The weights should return to their rest stops under spring pressure alone. Note that many distributors look the same, but have different springs and weights – so be sure it hasn’t been wrongly-substituted at some point. Make sure the baseplate and the shaft of the distributor aren’t loose or sloppy.

Next, set the points gap (if applicable) and ignition timing. It’s best to do this using a strobe at the slowest-possible idle, which eliminates any backlash in the distributor and its drive. Make a timing mark 180° from the main one and place the strobe on each HT lead in turn to check that all four cylinders are firing at the same BTDC angle.

Check vacuum pipes and the servo hose for looseness, splits, chafing and other defects. Double-check that all are on their correct stubs. Disconnect the servo hose from the inlet manifold, press the brake pedal a few times to exhaust the vacuum, then suck on the hose. You’ll suck a lot of air out, but eventually, you’ll be able to extract no more. If you can just keep on sucking, change the servo or its one-way valve.

Next, turn your attention to the carburettor. Make sure the correct one is fitted – or at least a manufacturer-approved alternative. Set the float level correctly and precisely, and make sure the filter at the inlet is clear, if it has one. For a fixed jet model, blow out all jets paying special attention to the main jet(s). If there’s a full-load enrichment valve, make sure it’s working. Some are mechanically-operated (check linkage and adjustment) and others simply draw fuel from the float chamber through a tube or nozzle placed in the airflow. Ensure any pipework is firmly seated and the drilling in the end is clear. If it takes the form of a small casting on a gasket, check the screw is tight and the gasket is sound. In the case of a Stromberg carburettor, make sure the diaphragm is not split.

If you still have no joy, scrutinise the fuel system. Check the delivery pressure of the fuel pump is 4 to 5psi. If it’s

too low, increase it by reducing the thickness of gasket(s) between it and the engine. If the pressure gauge flutters badly at idle, the pump valves are leaking: replace or rebuild.

Check all pipework between the tank and the pump. Replace hoses that are perished or over five years old and any disposable filters of uncertain age. Look for kinks or folds in all hoses. Check the state of the filter on the tank pickup and make sure the tank is venting properly, either via a ventilated cap or a vent hose. Inspect the metal fuel pipe under the car for perforations, kinks and crushing. Change the pipe if nothing else brings any improvement, as it may be silted up or constricted by varnish.