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Topic review (newest first)

6515_Peter_Christie
2019-07-31 23:22:31

Hi Syd,

Pinking is caused by pre ignition, sometimes called detonation. The 'rattling' noise is caused by the live charge igniting before the piston reaches near the top of the compression stroke. Correct ignition timing will normally get rid of this problem.

Valve bounce is caused by over revving the engine to the extent that the valve springs can't shut the valves before the cams are pushing them back up again. Valve bounce is unlikely to occur in our mildly tuned engines which are hardly able to turn over at 4,000 rpm, never mind the 6,000 or so rpm where you might start to hear the ugly and damaging sound of valve bounce.

Regards,

Peter C. [6515]

5750_David_Ralph
2019-07-31 21:04:04

There are many possible causes for pinking. Unless you have altered the ignition timing and it has only recently started pinking it is unlikely to be a timing problem. Pinking is caused when the incoming petrol and air is ignited too early. This can be caused by something glowing red hot inside the cylinders so causing the petrol and air mix to ignite dependant of the spark plug. A build up of carbon can get to the required heat to cause pinking. As could an edge of the head gasket, valves or spark plugs getting to hot. A too lean petrol to air mix will make an engine run much hotter.

Before retarding the ignition I would suggest you check the ignition time. If it is correctly set then retarding it is unlikely to solve the problem. I suggest you do an internet search for "what causes an engine to pink" as this should help you understand the problem better.

Good luck tracking down the cause of the problem.

8617_Mr_Syd_Smith
2019-07-31 08:44:53

In my experience lead additives are expensive and do little to stop pinking. I have seen no other advantage with them, but no doubt others here will disagree with that statement.

Pinking or valve bounce is not good for the engine so you need to look into it.

My suggestion is to retard the engine timing slightly a touch at a time and do a test run between each tweak until pinking has been eliminated.

Retarding the timing will reduce engine performance so you do need to get the timing as near to best performance and no pinking as you can get it.

Hope you solve your problem.  Syd

Michael
2019-07-30 20:18:40

My Goodwood rattles when going up hill, which I now believe to be pinking. I've been advised to use a lead substitute or a higher octane fuel,but would retarding the ignition by a degree or two work as well? Do members recommend a particular brand of lead substitute? I used to use Valvemaster but found it ran better without it with no pinking...

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