80,s landcruiser on gas burning valves

My 4.5lt Troopy has been on gas for approx 90,000ks. To date there is no indication of the problem. About 5,000ks ago I had it digitally tuned and checked (it was wired up like a person in hospital), it came out with a totally clean bill of health.

Ken,

The THIRD time?

Gas conversions on the 4.5 engine have a service life of around 250,000klms before the valves have receded so far that the head needs to be reconditioned. If you haven't been doing this sort of distance between recons there is something wrong!

The reason that the valves recede is purely the heat of combustion, so you should be looking for issues that increase this. Take a look at the fueling - are you running too lean? This is a common problem as people move to gas to save money and the converters often make it run as leanly as possible in an effort to reduce costs.

At least in the short term!

Have you fitted a snorkel ? Contrary to popular opinion a snorkel with all of its twists and turns will actually reduce air flow in normal driving. The "ram air" effect only comes into practice on the freeway and it can then cause the mixture to become very lean (and burn valves) as a result. The gas technicians have a very difficult time with snorkels.

Best advice is, if you intend keeping your truck for more than the 250,000 klm limit, don't use gas. It is a short term economy.

It obviously also reduces your outback touring capability which is the strong point of the big Toyotas.

Good luck.

Joe