Outer Limits 4x4 Board

I have been reading the forum and I have the option of putting my 1998 3.2 litre auto twin cab on gas - I have noticed on the forum that this might not be a good option. - are the older 3.2 ltr better suited to gas than the new ones and why is it so?
Any opions appreciated

Why isn't it a good option?
Mines had gas for 6 and half years

Thanks sudso - My main concern was what I read on the forum - some say the petrol engine isn't always suited to gas - maybe the older engine is more supportive to lpg than the newer ones. Is this possible and did you have to accept that valves etc. will burn out etc. My 98 model has onle 84k on the clock so I think it is still in exceptional condition.

reg w wrote:Thanks sudso - My main concern was what I read on the forum - some say the petrol engine isn't always suited to gas - maybe the older engine is more supportive to lpg than the newer ones. Is this possible and did you have to accept that valves etc. will burn out etc. My 98 model has onle 84k on the clock so I think it is still in exceptional condition.

I think the "older" 3.2 you are referring to is the single overhead cam engine which only came with earlier 90's Jackaroos.
The Rodeo's like yours and mine only came out with the later 3.2 DOHC
by then the Jackaroo's had the 3.5's.

I've read here and there on some forums that there was a factory approved LPG system for the later 3.2's, I dont know what systems they were though, maybe a Holden dealer can help there.

All I know is that LPG like petrol needs to be run at the right mixture especially not lean as either fuels when run lean too long can burn out valves but LPG does it quicker as it has a slightly higher combustion temperature.

If you want full insurance and dont mind spending more get some "hotter" valves and valve seats fitted that can handle accidental lean mixtures.
Keep in mind though that todays LPG processors are pretty reliable.

Also some LPG installers will insist on upper cylinder lubricant added to the gas line but one installer I spoke to said it's not necessary on all engines, it's neither here or there and the lubricant can eventually foul up plugs etc. and especially sensors in the fuel and exhaust path which will send your ECM messages to alter the fuel mixture unnecessarily.

Dont take my word as gospel though, pick as many brains as you can especially LPG installers and mechanics who fix LPG cars before you make your mind up.
Good Luck

thanks very much for your info - I will definitely get it done - I think the way the fuel prices are going its an obvious choice, but as you say there is no harm in asking a few different installers and trying to see which ones are better.

All unleaded engines have hardened valves and inserts. The main problem with early LPG coverted vehicles (pre Unleaded) was the lack of lead in LPG causing valve seat recesion. Incorect LPG mixture can cause higher combustion temps which can cause pre ignition and overheated valves. A EFI based feed back system, which takes mixture readings from the O2 sensor should lessen the chance of this.
I would leave the heads alone and maybe use an upper cyl lube kit if you are worried about valves.

All info greatly appreciated - thanks

I called into one of the local gas guys to ask about our '99 3.2 tray-back. He said that to do it properly we'd have to get nickel plated valve seats - or something along the lines of that.

Cheers

Some engines are better than others, Toyota cruisers and prados with bucket shim valve adjustment are prone to recession of exhaust vaves as are rodeo v6 and jackaroo with same engine(they also crack the intake manifold insulator spacer causing vacuum leaks), vs to vx v6 commodore engines(poor induction hardening of seats) as is the case with most pre unleaded cast head vehicles. LPG does burn a little hotter, much worse if the mixture is too lean or even over rich. This heat cannot be dissapated quickly enough to the exhaust valve seat when the valve is on its seat and the valve "burns" or receeds. Keep the valve clearances on the loose side, actually check don't listen to the noise as a guide as often the inlet valves which run much cooler due to the incoming cool intake air will stay looser and sound right while the exhausts are tight.
Look for the signs, rough idle, check your valves, get the mixtures checked on a chassis dyno every 40 000 klms.
All the avove mentioned engines will benefit from hardend valve seats, also refered to as stellite or black valve seats. I'd wait till the heads fail before pulling them off, if looked after they will give a couple of hundred thou klms of use as they are.
Joel

The 3.2 valve seats are as hard as fck. It's the factory valves that need replacing with harder aftermarket ones even if you dont have gas.
The factory valves are kind of sacrificial lambs so to speak.
The DOHC 3.2 is a fantastic motor, just a bit thirsty.