4.6 gems top end tap

The most cost-effective solution is, I'm afraid, a replacement block.
Any of the 94mm bore RV8's (ie all except the original 3.5) can suffer from this serious fault. There is some evidence that the higher combustion chamber temperatures experienced whilst running on LPG can exasperate liner slip, hence my question 'did it in initially tap on LPG' but not on petrol?

It sounds like a liner to me. Mine started tapping on LPG when fully warm, then on both fuels when fully warm, then after about a minute of start up. Mine was just a liner slip so no coolant loss just a tap that got louder & louder until you could hear the car ticking over from 200m away. Pinning the liner could be an option if your not loosing coolant.

martynv8 said:

It sounds like a liner to me. Mine started tapping on LPG when fully warm, then on both fuels when fully warm, then after about a minute of start up. Mine was just a liner slip so no coolant loss just a tap that got louder & louder until you could hear the car ticking over from 200m away. Pinning the liner could be an option if your not loosing coolant.

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Your experiences mirror mine on a 3.9 several years ago. The most galling thing for me was when someone heard the bloody thing tapping away at idle & said 'is it a diesel?'

norseman said:

Your experiences mirror mine on a 3.9 several years ago. The most galling thing for me was when someone heard the bloody thing tapping away at idle & said 'is it a diesel?'

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LOL....had a similar comment on mine......that's when i decided to get a top hat block rebuild.