Valve Seat Recession with LPG

[Flat_White]

Just got the VY converted to a SPRINT GAS mixer type LPG system... i am a little concerned about the issue with LPG destroying my valves, i have heard of the drip lube system but is it worth installing... i know lpg is saving me money now but i dont want it all to be wasted on getting the valves/heads redone... has anyone ever had an issue with valves and LPG in a commodore?

also, please do not make this thread a battle ground for lpg users vs anti-LPG nazi's...

cheers for any advice

[Cursed CX8]

im pretty sure the sprint gas system starts the car on petrol and then converts to gas after 3 seconds or when the revs go above 1500rpm. This means that the injectors and valves are still getting used occasionally and will remain in usable condition. Its recommended that the car be run on petrol occasionally to maintain the fuel system.
Id suggest that with every second tank of petrol that you use, add a little valve saver/top end cylinder lube to stop the recession, maybe even some injector cleaner.
I know that every second tank seems alot, but if you think about how long one tank of fuel will last, especially if you only buy petrol once a month and gas the rest of the time

[Flat_White]

im pretty sure the sprint gas system starts the car on petrol and then converts to gas after 3 seconds or when the revs go above 1500rpm. This means that the injectors and valves are still getting used occasionally and will remain in usable condition. Its recommended that the car be run on petrol occasionally to maintain the fuel system.
Id suggest that with every second tank of petrol that you use, add a little valve saver/top end cylinder lube to stop the recession, maybe even some injector cleaner.
I know that every second tank seems alot, but if you think about how long one tank of fuel will last, especially if you only buy petrol once a month and gas the rest of the time

Correct, the system starts on petrol, then instantaneously switches to gas. you bring up some interesting points.

[commsirac]

Just got the VY converted to a SPRINT GAS mixer type LPG system... i am a little concerned about the issue with LPG destroying my valves, i have heard of the drip lube system but is it worth installing... i know lpg is saving me money now but i dont want it all to be wasted on getting the valves/heads redone... has anyone ever had an issue with valves and LPG in a commodore?

also, please do not make this thread a battle ground for lpg users vs anti-LPG nazi's...

cheers for any advice

You need to weigh up whether costs and perceived benefits.

The flashlube systems have been on offer since lpg has been around, originally aimed at the cars that had converted from leaded petrol to lpg. Whether the flashlube system was necessary here was debatable, many lpg users putting huge distances on conventional leaded motors without needing to redo the cylinder head valves etc, myself included.

An unleaded petrol motor has harder valve seats etc to start with, as there are no substitute lubricants in unleaded petrol(afaik), though there is supposedly the valves wont get as hot due to vaporisation of the petrol in an unleaded motor(inlet valve at least), but its the exhaust valves that apparently are affected most.

Certainly lpg fitters may recommend it, as they sell it and fit the systems, but whether it is really necessary or will actuallyavert cylinder head damage on current unleaded motors, there is no clear evidence.

Personally, I wouldnt bother, the chances of having to rebuild the cylinder head in the time/km you own the car seem relatively small with most comm users reporting high lpg mileages with no problems.

While some would say its cheap insurance, do the sums, how much will it cost to fit the system and keep feeding it and how much are you effectively trying to safeguard? whats a reconditioned cylinder head on a comm going to set one back if the worst does happen?

[jules]

Personally, I wouldnt bother, the chances of having to rebuild the cylinder head in the time/km you own the car seem relatively small with most comm users reporting high lpg mileages with no problems.

a mate of mine works as a design engineer (as an engineer, i know a few vehicle design engineers) for a large manufacturer of vehicles in close proximity to most of us.

they apparently use hardened valve seats if LPG is specified by the purchaser and the results can be fairly nasty if the soft ones are used. i'm not sure if that still applies to the current model.

it really depends on the type of engine - some manufacturers use harder seats than others - but if you're talking Commodore...

[Pub247]

You need to weigh up whether costs and perceived benefits.

An unleaded petrol motor has harder valve seats etc to start with, as there are no substitute lubricants in unleaded petrol(afaik), though there is supposedly the valves wont get as hot due to vaporisation of the petrol in an unleaded motor(inlet valve at least), but its the exhaust valves that apparently are affected most.

Everything you say is pretty much correct except the above bit i've quoted. Any holden cast iron motor whether its 202, V6 or V8 the seats are actually cut from the cast iron itself. Exhuast valves are the worst affected though inlets can suffer aswell. You're right in saying that it'll be a long time before you get any serious recession easily about 80,000klms. When we reco heads at work they are all fitted with hardebed valve seat inserts to suit gas or petrol.

a mate of mine works as a design engineer (as an engineer, i know a few vehicle design engineers) for a large manufacturer of vehicles in close proximity to most of us.

they apparently use hardened valve seats if LPG is specified by the purchaser and the results can be fairly nasty if the soft ones are used. i'm not sure if that still applies to the current model.

it really depends on the type of engine - some manufacturers use harder seats than others - but if you're talking Commodore...

YEs true some are harder than others Ford typically use a hardened seat in there new models. All alloy heads run an insert but they materials theyre made from vary from manufacturer. Toyota commercial are they worst i reckon its very easy to tell which have been on gas and which havent

[deserthead]

Our six has been on gas for over 2 years now, I got the flash lube installed wen it got converted. Only cost $100, so cheap piece of mind.
It hold a litre in the bottle and we've still got 200ml left so it doesn't need to be filled very often. . . . .

[commsirac]

Our six has been on gas for over 2 years now, I got the flash lube installed wen it got converted. Only cost $100, so cheap piece of mind.
It hold a litre in the bottle and we've still got 200ml left so it doesn't need to be filled very often. . . . .

Fair enough, the other point worth making is, does flash lube actually do what it claims to do, or is just another feel good accessory for enthusiasts, like lpg oils etc?

My own personal fleet of five lpg powered vehicles, which Ive managed/serviced since the early 90s dont have it and are all still purring along........ if Id outlayed for five flash lube setups and fed them all that time....it would be hard to justify the money spent?

[Flat_White]

Fair enough, the other point worth making is, does flash lube actually do what it claims to do, or is just another feel good accessory for enthusiasts, like lpg oils etc?

My own personal fleet of five lpg powered vehicles, which Ive managed/serviced since the early 90s dont have it and are all still purring along........ if Id outlayed for five flash lube setups and fed them all that time....it would be hard to justify the money spent?

3 questions for you... are all of those cars commodores? are they factory or aftermarket conversions? how often do you run petrol?

cheers.

[Flat_White]

also guys, just wondering what your opinions were on the Nulon fuel additive for LPG valve seat recession, i saw it at big W today, it was 10bucks for a reasonable sized bottle, it said use 1ml per litre of petrol you add.

anyone know much about it?

[commsirac]

3 questions for you... are all of those cars commodores? are they factory or aftermarket conversions? how often do you run petrol?

cheers.

only one is a v6(fact setup), the others are 202s.....and a falcon....run petrol in the v6 only by default when it uses a squirt or so on cold startup. the 202s are straight lpg

[deserthead]

Fair enough, the other point worth making is, does flash lube actually do what it claims to do, or is just another feel good accessory for enthusiasts, like lpg oils etc?

My own personal fleet of five lpg powered vehicles, which Ive managed/serviced since the early 90s dont have it and are all still purring along........ if Id outlayed for five flash lube setups and fed them all that time....it would be hard to justify the money spent?

I only went the flash lube, for the piece of mind thing. Honestly I have no idea whether it works or not. So far so good.
But I've also not have to had to change the leads on the car in 4 years, two of those on gas.
So for me, the only reason was piece of mind.

Out of curiousity have u had any, of the "long term" probs, ie valve recession, with any of them?

[Flat_White]

whats everyones opinion on NULON fuel additives. I saw some at bigW 10bucks for Valve saver fluid, seems like a good deal but is it worth it?

[VL Berlina 5speed]

well ill tell you from personal experiance

my vs currnetly has 380,000km on the clock, we have owned it since about 50,000km and the car is factory gas

we have not had any head problems what so ever in this car and it still runs perfect.
we have ran a drip system on this car since we got it and this could possibly be the reason no head problems have happened,

we just keep toping it up when needs be and double check its drip rate is on time when we service the car, simple and no problems at all

[Flat_White]

Sorry, im digging this one up again.

Just wondering, worst case scenario, the lpg F**ks the valves, what would be the reconditioning cost for these, i really cant see me owning this car much past another 50,000kms... Im just trying to add up whether its worth 120 bucks to get this damn flash lube installed.

[deserthead]

Dude, if ur only planning on keeping it for that small amount of k's, I personally wouldn't worry about it.
You have to remember too that you only hear about the worst ones mostly.
I'd not worry about it. Its only another 2yrs of driving, our car has been on lpg for longer than that already and has had no probs.