Pinking and Worn Mechanical Advance
Pinking is down to over-advanced ignition timing. Sometimes the ignition timing just needs to be retarded.
If you really know what you are doing, have properly serviced the ignition, have set the timing and still have annoying pinking problems then Frederick's suggestion might be worth a fiddle. Otherwise there be dragons on this page (not just frogs) so don't read any further.
Renault 4 GTLs have a tendency to pink. But you can swap the distributor for a really low mileage one and cure the problem.
The Gordini also had a tendency to pink at 2000rpm on anything other than light throttle. Distributors for Gordinis are a little more tricky to get hold of so it was worth finding a fix.
The Gordini was generally too advanced at part throttle but if the ignition was retarded it would be too retarded to take sudden full throttle at higher revs without dying. Also the timing was unstable at idle and town driving was lumpy.
Frederick the frog to the rescue!
The distributor is 30 years old. The people that rebuild them reckon they fit slightly shorter springs to compentate for wear in the mechanism (and any stretching in the springs).
There are two springs inside the centrifugal advance - a thick one and a thin one. The thick one should have some slack - it only controls the advance from about halfway (2000rpm maybe). Below that the advance is controlled by the thin spring which should not have any slack. Mine was slack.
The springs are mounted on posts which can be bent back with some long nose pliers to take up the slack. I bent both of them back a little and it transformed the Gordini - now it seems to be very flexible about how the timing is set up and the pinking is gone.
I'll get more scientific about this at some point and update the page.
Had I been scientific I would have marked the flywheel with timing marks at maybe 5 degree intervals, then checked what the centrifugal advance was doing at 500rpm increments, then plotted that on a graph to compare with the factory settings. The graph should show where the advance curve starts advancing (little spring) and then when it starts advancing more slowly (thick spring) and tell you which spring post needed bending a little.
I've got the numbers for the Gordini and will fine tune at some point, but I don't have numbers for the Renault 4 GTL.
If you have pinking try bending the post with the little spring to take up the slack and the post with the big spring just a tiny bit. That's all I did and it worked wonders!
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