Classic cars forum & vehicle restoration.

[Bitumen Boy]

[norustplease]

I ran two successive Subaru estates on LPG, without any mishap. However there is a potential issue of valve seat recession and I moved both on at 50K miles, which was reckoned to be the mileage beyond which things could start to go wrong . The following is a quote from a website on the subject:

LPG once vaporised is a pure vapour and has no lubricating properties at all, this then passes through the inlet valves and into the cylinder where it is ignited by the spark plugs, combustion takes place and the hot spent gasses exit through the exhaust valves.

Because these gasses are very hot and contain no lubricants or additives they very slowly start to burn the valve face and valve seat of the exhaust valve away, this process (called recession) over time eventually causes the valve to recede in to its seat eventually reducing the valve or tappet clearance to zero. Once this has happened it is only a matter of a few miles before the valve head starts to disintegrate causing loss of compression and misfire. This will also lead to catalytic converter failure if the vehicle continues to be driven with misfires by way off unburnt fuel passing through the exhaust system to the catalytic convertor.

Flashlube helps, but isn't a complete cure.
The following website gives quite a lot of information on running Land Rovers on LPG and is worth a read.

http://www.amrautos.co.uk/index.php/lpg-systems
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1953 Citroen Traction
1964 Volvo PV544
1957 Austin A55 Mk 1
Boring Tucson SUV

[emmerson]