This is an extract from an article on the main GCA website – (accessible from a desktop, tablet and not from a mobile phone) The article is mainly directed at owners of Classic Range Rovers and Discovery 1 and 2 models.
The simplest “fix” for a 3.5 V8 is to change it to a 3.9 litre engine or even a reworked 4.6 engine. Vehicles already fitted with 3.9 engines can also be upgraded and/or have reworked 4.6 engines installed. Neither are cheap options, but the results are frequently outstanding. Additionally, the work is usually less expensive than replacing the vehicle, by the time all associated costs are taken into account – like insurance, financing etc. The outcomes are also predictable, whereas replacing one vehicle with another may not always be the better option.
Arguably, the best option is to change the power unit wither to a 4.0 litre or 4.6 litre engine taken from the P38 Range Rover. The major problem will be finding a suitable donor engine. If they were any good, they would probably not be available in the first place but regardless, complete reliability will only be achieved by a thorough rebuild that will include the fitting of “top hat” liners, cross-bolted mains, reworked heads, filters, gaskets, and so on
The best solution is to engage in a serious dialogue with a workshop with proven practical experience in modification and upgrade work – certainly available from the specialists at Graeme Cooper Automotive.