Many petrol engines are non-interference, its extremely unlikely for a Diesel engine to be non-interference due to the high compression required.
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Actually the vast vast majority of petrol engines are interference too, some of the limp fiat engines are supposedly non interference but I have seen one which did just tweak a couple of valves.
. Garage recons its likely to have around 4 valves bent, with no damage to pistons etc.. although I've no idea how he would come up with that.
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