Just wondering, what caused the cylinder head to go? What actually failed, and did you get to the root cause? Was it running lean?
Did the LPG installer check the system for correct running?
I've been using LPG in loads of eclectic high performance cars for years, and never had any problems, but then again, I've always used a converter that really knew what he was doing, and paid close attention to the running of the car. In fact, I'm training to become an installer myself.
I've seen loads of bad LPG conversions in my time.
With simple errors, like the evaporator connected to the wrong point on the manifold, injector pipes kinked and blocked.
Incorrect size nozzles used.
There are loads of people claiming to do a 1 day conversion for less than £1k - I find this worrying. I cant see how thisis really possible without cutting serious corners in the installation and setup. There is a good 6-8 hours installation time in any lpg kit. Plus the setting up.
A good example is the cold start/ warmup check. This really needs to be done a couple of times to check the changeover is ok.
Also, there should be a good test drive, up to temperature, with the diagnostics plugged in and continually monitored to check the mixture, and to tweak the calibration. No matter whatnthe kit manufacturer says about "auto calibration" only a fool would rely completely on this, and not check it manually. The manual checks would highlight any lean running.
Also, many "kits" have a marginally specified evaporator. This would result in lean running and engine failure. There should always be adequate headroom in the kit specification, e.g. Using a 210 hp kit on a 200 hp car. You really need the 280hp kit to make sure you don't run into problems.
In reality, a good LPG Kit costs about £1k for the parts, with a fitting cost of between £500 to £800. For a 6 cylinder.
Yes, you get a poorer mpg, but only by about 10% if the system is installed and set up correctly.
On my Saab 9-3 Viggen (235bhp 2.3 litre turbo) I average 30 mpg on LPG, 33 mpg on petrol. On a run, I get 45 on LPG, 47 on petrol. From experience, this is typical on modern cars with knock sensing.
In some applications, like my tuned rover v8, the engine spec has been created to run specifically on LPG, with a high compression ratio. I have to run it very rich on petrol to stop detonation.
Power is reduced on LPG, but if you really want the full power, you can tune the LPG system to revert to petrol at full throttle, thus restoring the 10% ish lost power - this is particularly useful on smaller engined cars.
I'd be interested in finding out more about the 400h conversion - more details please.
Mike.