Engine rattle - 1975 116 280s

[stiffy]

G'day,

Anyway - when the car is under load (going up a hill in high gear) I hear this rattling sound. Doesn't change pitch but it only becomes louder the further down the throttle and only disappears when I back off or am only gently accelerating.

Could it be a loose timing chain? Tappets? Low octane unleaded petrol? - you can no longer buy LRP in Australia anymore, so apart from paying $1.30 per litre we also have to put an additive in it to protect the valves from overheating.

I had this happen on my older '65 230s as well and it was a manual - so I'm assuming it's not coming from the gearbox.

It sounds nasty and the car doesn't seem to have as much torque at the moment.

[Arthur Dalton]

The engine is pinging.. retard the spark timing a couple of degrees and retry ..

[stiffy]

Of course... I always thought pinging sounded different (it had been described to me as 'knocking' - which I assumed sounded different).

thanks.