Disco 2 with LPG conversion

A pal of mine is looking to buy a disco 2 with an LPG conversion but has been warned by someone else that the LPG system can cause the cylinder head to become porous. Is there any evidence for this?

yeh plenty of fooked engines around..

No evidence whatsoever

jonp said:

A pal of mine is looking to buy a disco 2 with an LPG conversion but has been warned by someone else that the LPG system can cause the cylinder head to become porous. Is there any evidence for this?

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no ,blocks crack behind liner giving head gasket failure symptoms (coolant pressurisation )some are more prone than others lpg per say shouldnt be a problem usually fault in cooling system ie inefficent rad ,leak ,unchecked coolant level ,thermostat etc,its been a problem with the v8 block since they first bored out the 3.5 an extra 200 thou to make the 3.9 ,4.6,4,and 3.9 litre engines share the same bore size

About ten years ago I had a 3.5 converted to LPG. It ran well but was prone to back-firing through the airbox. That was a Disco 1, though, where the LPG was introduced into the engine through the plenum chamber. Direct injection systems don't suffer with this, I gather.

Never had a problem with the engine itself though. I was told by the installer that LPG has detergent qualities meaning it would clean the accumulated carbon off the inside of the cylinder, and if the head gasket is at all suspect can lead to it failing.

I've been running a RR Classic LSE (4.2 litre) for 10 years and Discovery 2 (4.0 litre) for 4 years + Both on LPG. Absolutely no problem at all with either of them. I've read that people believe that LPG makes the bores porous but can see no evedence or logic in this

They do say that as long as the cooling system is a 100% there won't be any problems though lpg runs a high combustable temp than lead free.

But I wouldn't go near the stuff, I've read the stories about overheating V8s and then a slipped liner ... unless it's my bar-b-q.

I wouldn't go near a diesel - I've heard stories of them running on their own oil and HG failure....

Lpg doesn't burn hotter, it just gets hot quicker.

Planny said:

Lpg doesn't burn hotter, it just gets hot quicker.

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We all know that, it has a lower calorific value, but the engine will run at a hotter temperature.... something not wanted in an alloy V8 engine.

Look at Other differences in this link. Go LPG - Will the performance of my vehicle be any different when using LPG?

Yes you have read that on some forum but have you got any experience with a v8 on lpg?
Mine gets no hotter on lpg than on petrol, it has done over 97k since conversion

lpg is fine if cooling system is fine as with petrol, stop just reading about stuff on google and learn about v8s from 3.9 on blocks cracking and why ,

Thanks to everyone who replied. This is all helpful.

Had two 3.9 one on lpg not a problem with them had a 4.6 was going to have lpg fitted but to many problems.The ones that appear to have the biggest problems with the blocks are the ones with lucas gems injection systems as it leans the mixture right down when running at a set constant speed.

discool said:

We all know that, it has a lower calorific value, but the engine will run at a hotter temperature.... something not wanted in an alloy V8 engine.

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Don't understand - if lpg has a lower calorific value it can't run hotter, assuming that the injection system is working correctly and the engine isn't running lean???

thebiglad said:

Don't understand - if lpg has a lower calorific value it can't run hotter, assuming that the injection system is working correctly and the engine isn't running lean???

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LPG is not my field so I'm not that interested. So I can only read stuff on whe www and makeup my own mind, as the previous posted link, which states engine runs hotter.

Re the engine temp on lpg as related in that article, it makes no sense to me at all.

1. LPG has a lower calorific value and burns at a lower temp

2. Just because it's takes micro-seconds less to flame and therefore expand does not in itself create more heat.

3. It is of a higher octane than petrol which means the engine can run on different timing, if required.


Bottom line real life experience seems to be that LPG'd petrol engines work well enough, but lower power and lower mpg.

They always give lower mpg and even when taking into account the difference in price per ltr between 95 u/l and lpg in France:1.52€ versus 0.90€ does not show lpg as half the price of petrol.

So, taking into account a lower mpg on lpg plus the fact that lpg is not as cheap relative to petrol as it was, I can't see it stacks up. Then if you take into account that an lpg-equipped car has, by definition, 2 complete and separate fuel systems, you have double the possibility of problems.

So what's the advantage of a V8/lpg Disco? Yes, it is more powerful by comparison to a TD5 in std trim - but the TD5 can have it's power and torque increased significantly at really quite low cost. A TD5 remap from a reliable source can be effected from as little as £225. This will increase power from 136bhp to about 160bhp with big gains in torque, particularly in the rev range 1500 to 3000rpm.

Just my 2 penn'th

The only thing that gets hotter is the valves as LPG is drier than petrol vapour, but Disco 2 V8 doesn't suffer from valve seat recession as quite a few other engines do