Hi Guys, I'm a bit late to the party on this thread but I've only just joined. I run a gas yard that sells LPG and obviously I get to see a lot of converted cars and to chat to their owners. I've just purchased a 2005 LS430 from one of my regulars it's just nicely run-in at 304,000 miles, 250,000 of which were on LPG. Anyway point is:- Yes you can successfully convert most engines prior to the advent of direct petrol injection which has created a whole raft of problems in itself. I have seen and experienced valve recession in a number of engines but there doesn't appear to be a hard and fast list of suitable/unsuitable engines for conversion.