Classic cars forum & vehicle restoration.

[1963EJ]

I was wondering why the term "engine knock" is sometimes applied to pinking? On my 6 cylinder Holden engine I am getting a knock at around 2200 rpm, 40-45 mph in top. Its like a throb, a bit "hammery" sounding and also results in a slight vibration through the gas pedal. I dont believe it is engine wear as there is no noise at idle or revving up in the driveway, and if I accelerate through to 55 mph there is no knocking, sounds nice and smooth. I have also had a good listen all around the sump area with a mechanics stethoscope and wasnt able to detect any major main bearing noise.

So was wondering if what I am experiencing is a form of engine knock due to incorrect timing? The is no "pinking" sound (tinkly sound) at all if I push her hard up a hill at low revs in top gear, so had assumed advance wasnt the problem. But could this "knocking" be another form of pinking?

Would be really grateful for any ideas/opinions

[ukdave2002]

Hi

It might be piston slap, I had a 911 with a noisy piston at a certain rev range, was advise that it didn't warrant any major surgery .

Dave

[JohnDale]

Hi EJ,could be incorrect timing at that particular RPM possibly caused by week/broken dizzy bob weight spring or wrong heat grade of plug causing pre-ignition. Could also be rubbish fuel if it's anything like our rubbish here in UK & so requiring a slight retard of timing. Don't know why it would vibrate the gas pedal unless there is a mis-fire at the same time.Cheers,JD.
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1958 Ford Zephyr Mk2 Convertible
1976 Ford Granada Ghia.