The V8 Owners Forum -

Hi Chris
"Hey, guess what, I don't entirely agree with Mike."
you know something I thought you would say that!
Best regards
Mike

I see... Well I have been thinking about putting a set of ported heads on anyway, so I might do all of the above! Probably in increasing order of severity starting with the hot compression test and moving progressively closer to my bank manager....

I can see I have entered myself into an ongoing debate about LPG which I must admit I don't understand enough about. The car had an lpg conversion when I got it, and being a PhD student, I need to long journeys (up to 800 mile round trips once every month or so, as well as normal driving) on a tight budget, an am a selfish lover of the rover v8, so at least for now I am going to keep feeding the lpg to the animal and hope it doesn't belch too much.

In terms of improving the reliability of a petrol engine running on LPG is there anything I should do when I get the heads rebuilt (If I get the heads rebuilt?) Should I raise the CR of the engine, and if so do I need to worry about valve - piston clearances on a std. cam? Would this also mean I need to run studs instead of std. cyl head bolts? Are there better materials for valves? Should I avoid 3 angle seats?
I guess this is a topic for the LPG forum...

TOOOO many questions eh?
Sorry, I am tenacious! It comes with the job.

Hi
Sorry it is a dabate I usually try and keep out of but at the moment there are two threads I am chipping in on, both RV8s with mysterious problems both running LPG and I have ended up commenting on LPG again, even though the LPG section is the one section on here I never even open!
From where I see it there are some people who have success with it and some that don't. As a general rule those that have success with it build their engines around LPG, spend alot of time sorting it out themselves and become experts in their field, generally but not exclusivly they go over to running only LPG starting on the stuff, never run it on petrol. The ones that don't are like me in that they try and fit and forget, someone else fitted the kit and you just try and run it and save on fuel costs. Generally they ( I ) are ok for about 30 to 40K then the engine dies with symptoms of a totally knackered top end, head gasket gone, running rough and on further investigation the exhaust side of the heads are shot to bits, valves receeded into the seats, rough looking ports, crached heads around the ports valves that rattle in the guides and in my case the inlet tract was blown to bits from it backfiring all the time.
I did alot of reading and research on LPG as my engine was dieing and came to the forllowing conclusions
1 LPG burns relativly slowly compared to petrol
2 It's octain rating is very high
3 the quality of LPG, especially the amount of water in it from different garages varies alot
4 It has virtually no lubricating properties
to get around these and make the best of these properties you need to
1 have a cam that opens the valve relativly late in the exhaust cycle compared to petrol so what goes out the exhaust has finnished burning, but with less timing and alot more lift so you dont have issues with overlap.
2 have a very well mixed charge before you try and light it
3 hit it with a big spark (or two) that is very acuratly timed
4 Up the CR to take advantage of the high octain (and help all of the above)
5 find a reliable source of LPG and only buy from there
6 worh out a way of improving valve guide lubrication, probably groves down the giudes and get rid of the oil seals, or use sintered guides that have a metal lubricant in them.
The ideal is an engine with a very tight squish band, CR about 11.5 or 12:1 very good exhaust flow (2 exhaust valves, 1 inlet) and 2 plugs spaced on opposite sides of the combustion chamber and a high swirl inlet port and fast burn combustion chamber.
The net result though is an engine that will pink like mad on petrol and you can only build a few of those into the rover . what you can do is up the CR, close up the squish band, fit megajolt firing wasted spark triggered off the crank and bin all the petrol side.
Anyway I shall step back out of the debate on LPG
Best regrads
Mike

mosesthemonk wrote:whether running on petrol OR gas I still get a bit of white 'steam' out the exhaust.

One of the byproducts of internal combustion engines is Water, which will show up at water vapour (steam being invisible) exiting the exhaust system, particularly on cold days. My petrol V8 in good condition produces a veritable fog, on some cold mornings and it has nothing to to do with coolant leaking into the combustion chambers

this is worst when the engine has sat for some time unused, and then first startup, so I presumed this could be due to residual pressure in the coolant system forcing coolant into the cylinders.

If there was a leak into the combustion chambers then the pressure would soon dissipate when the engine is switched off, but from my prior comment its more likely to be the H2O byproduct of the combustion process.

There is no residual pressure in the cooling system at start-up. Pressure builds slowly during the warm-up phase topping out - usually - at 15 psi or whatever the pressure release cap says on the lid.

My next step will be to do a hot compression test, as I have been told elsewhere that a cold one is useless

You already found out that all the cylinders were reasonable when cold and did not vary much, one to another. You can relax in the thought that you are unlikely to have a breached head gasket.

the smell in the header tank is not strong - should I watch the header tank for bubbles with the car running?

coolant going around an engine is bound to pong a bit to which I would not attach too much significance, particularly as the amount of Smell is (as is Beauty) in the eye or nose of the beholder.

A constant stream of small bubbles in the header tank is a possible sign of a slight head gasket leak - obviously the more there is the more the likelyhood - but might also be confused with trapped air being ejected.

Once the trapped air is expelled forever, then a bubbles symptom can be taken as being more significant, but only then.

How do make absolutely sure I have bled the system of ALL bubbles?

Read this

http://www.vintagemodelairplane.com/pag ... ant01.html

and work out how it can be applied to your particular cooling layout - of which I am not familiar - but the process holds good for most engines.

There is another way I recently came across

Modify a spare pressure cap with a 3 foot long vertical tube, brazed on, topped off with a funnel full of coolant.

Run the engine from cold and as the air is expelled by the circulatory and heating process so it is replaced by coolant until no more air exists in the cooling system innards. QED

If these things do not show faults is it still worth popping the heads off and having a look for what I find or should I run away and hide?

If you have a good reason, or an insatiable desire, to remove the heads then do it. If AFTER you have suffered a couple or three broken head bolts, then you may wish for a hiding place, where none exists.

Got me worried now Mike!

My 60K engine was built with 10.5:1 pistons, but standard Range Rover apart from that, and lasted OK.

The P38 is completely standard Thor, we shall see.....

Chris.

Hi Chris
My intention was not to worry anyone, I was hoping to point out the need to understand that LPG is under developed as a fuel in car engines and that it is as a result necessary to take on that development yourself. You seem to be one of those who keeps a very close eye on your vehicles and I suspect as a result you will have much less trouble than I had, 10.5:1 cr is a good step in getting the stuff to burn, the more modern ignition on the later RR engine will also help alot, but things wear and LPG seems very unforgiving on old parts. I still think dual fuel is a very bad idea as you cant have such both a high CR and late opening of the exhaust valve for the LPG and a much lower CR and earlier exhaust event for the petrol.
Getting back to the posters questions.
If you skim the heads/block enough to raise the CR and narrow the squish band you should check the valve to piston clearance, I think it will be ok but it should be checked. Don't worry about studs, the bolts will be fine. Good stainless valves will be fine for the heads, yes a 3 angle valve job is worth while, but leave the seat a bit wider than for a petrol engine.
Best regards
Mike

Hi mosesthemonk.
It is my opinion that it would be prudent to solve the left and right spark plug colour missmatch before you proceed with removal of the heads etc.
You haven't mentioned how it runs and if the MPG is good or bad. All this info helps.

The suspected water loss and apparent steam from the exhaust is very unlikely to be influencing the spark plug colour given that all 4 plugs on each bank are the same colour. Reason, it's not likely that the gasket is leaking on all four pots and or all four liners are defective.

I assume the lpg system has a single point feed to the plenum which would rule out the possibility of uneven distribution to each bank.
It would help to know if it's not a single point entry.

As a starting point I would check the wiring to the lambda sensors and check for the 12v feed. There is a wiring diagram for the EFI elsewhere on a sticky on this forum. Unless you have a digital voltmeter you will not be able to check the output on the sensor wire.
You could try swopping the lambda sensors over for a few days and see if there is any difference to the plug colours. If nothing changes then at least you have eliminated the Lambda sensors.

As you know all engines chuck out an abundance of steam when first started from cold and the fact that one bank is indicating a rich condition, will in itself influence the amount of steam from the exhaust. An over rich mixture will result in free water and steam in the exhaust.

Regards Denis

How about swapping the injector leads from left to right

If the "lean side" follows the move you have an electrical fault

If not you have faulty injectors on one side

Ian

Hi!
I will check and see what sort of LPG system it is when I get home, I'm afraid I don't know off the top of my head!

You could try swopping the lambda sensors over for a few days and see if there is any difference to the plug colours

this makes sense to me I can try this also but

How about swapping the injector leads from left to right

I am not sure I understand this - won't this cause backfiring if the car will even run, aren't the injectors timed? I'm sorry I don't know much about this sort of thing!
If not then I will also give this a go!



If I had airlocks in the system, due to mu dodgy top-up method this could presumably have led to my 2 inch drop in coolant levels when it belched into the header tank. I have not noticed a loss of coolant since, but the steam seems more than when I first got the car, and I'm not convinced this is ok, but the uneven fueling could also cause this.

I can take photos of the spark plugs before I clean them, then I'll clean them and replace them run for a bit w/ lambdas swapped and take new photos, and see where it takes me!

Thanks again as always!

Hi again!
I have some updates:
I isolated the LPG system from the coolant system, and am servicing the LPG vaporiser. There was no apparent change in the problem, still steaming! The lpg system also seemed to be in good condition so I cannot assume it was pressurising the coolant system.
With the vaporiser removed I ran the car for a few minutes, with the expansion tank (coolant reservoir) cap and the top radiator cap off. I topped up the system through the reservoir, and let the coolant drip slowly out of the radiator.
The radiator bubbled at the rate of one bubble (about the diameter of a 20p coin) every 2-3 seconds for 20 minutes without any sign of stopping. It was constant, and wasn't faster at first as I'd expect if it were a problem with airlocks in the system.
I had a look for the lambda sensors, and found only one which was on the 2-1 downpipe of the left bank. I presume this is from the LPG system.
I guess it is possible that someone replaced the down-pipe on the right bank and bought the wrong one so ignored the lambda sensor.
Is there any way of knowing if my car is a pre-lambda model? (Other than it having lambda sensors) If not, where do the sensors normally lead to so I can look for cut wires.
My injector leads are hard to reach and all tucked away in ducting behind the plenum, and made even more inaccessible than standard by the injector cut-out wiring for the LPG system, so I haven't had time to muck about too much with them.
However, with the advice and help of a friend I also now notice that my cloud from the exhaust does smell a bit rich.
I am not sure what to do as the bloody car runs fine and doesn't give me any bother, but it has symptoms which worry me.
My gut feeling is that the head gasket is damaged, but that there may also be a problem with the injector system.

mosesthemonk wrote: I ran the car for a few minutes, with the expansion tank (coolant reservoir) cap and the top radiator cap off. I topped up the system through the reservoir, and let the coolant drip slowly out of the radiator.

Hopefully then you have expelled all the trapped air.

The radiator bubbled at the rate of one bubble (about the diameter of a 20p coin) every 2-3 seconds for 20 minutes without any sign of stopping. It was constant, and wasn't faster at first as I'd expect if it were a problem with airlocks in the system.

If you were doing this with the pressure cap removed, you have to remember that the coolant would be boiling at or around 100 deg C at the hottest parts of the engine and the steam bubbles generated thereabouts would escape constantly.

With the pressure cap on, the boiling point is raised considerably to more like 120 deg C or greater, and those steam bubbles do not form so readily.

However, with the advice and help of a friend I also now notice that my cloud from the exhaust does smell a bit rich.

That smell is because half of your cylinders are running too rich as evidenced by the 4 sooty plugs on one bank.

My gut feeling is that the head gasket is damaged, but that there may also be a problem with the injector system.

In priority order, fix the overfuelling on the faulty bank and only when that is done and corrected should you move to the head gasket issue. And that depends upon the bubble situation when the pressure cap is in place and working correctly as mentioned above.

UNLESS you can establish that the missing lamda sensor is the problem, the most likely cause of the unbalanced overfuelling is a faulty ECU .

When I first fitted my 3.5, I too thought I had a head gasket problem because of the amount of vapour i was getting out the exhaust - in the end it was nothing to worry about, just a symptom of having a large petrol engine

Just to add my two pence worth, I have like Chris been running my 3.5 on LPG pretty much exclusively for the last 35,000 miles no problems at all.

My engine is rebuilt but standard- I am running standard 9.35:1 compression, and have no whizzy bits apart from Megajolt to get timing spot on and allow me to use different advance maps for petrol and LPG. I also have a wideband sensor fitted to allow to me setup fuelling correctly.

I think most people problems come from running their LPG too weak- before the LC1 I actually had the opposite problem, too rich!

From the symptoms I'd agree with Ramon, leave the LPG disconnected (for your peace of mind more than anything) then troubleshoot the rich fuelling you are seeing on one bank.

After that you can chase the water loss.

I periodically lose small amounts of water, and so far (touchwood) it has always come down to a jubliee clip that needs a little nip up or something. Just keep an eye on the level and top up as required for now, remember the water loss is not a problem as such, but running out of water definitely is!



Good luck

I have been reading this thread and it has I think settled a few things for me, especially the lambda sensor issue, I replaced my spark plugs a few days ago and found exactly the same thing, the right bank was sooty and the left bank was completely normal, leading me to think along the lines of the lambda's.....

I have a sensor on each of my down pipes and will probably replace them both as a pair to keep things equal, if ones gone now the other wont be far behind.

I was reliably informed by a mechanic in a conversation about fuel consumption that timing and lambda sensor operation are key things to note along with the usual suspects of plugs, leads, caps and coils, there are many many more but these are the main culprits.

I read with great interest the points made about the lack of lubricity afforded by the LPG and I know that PRINS auto gas does a lubrication system to run in conjunction with the LPG system, it claims to reduce valve wear and aid cooling of the valve stems.

Will only consider it iff my mileage increses dramatically!!!

Hi again everyone!
Thanks very much for all the replies! The single lambda is actually for the feedback to the lpg, and the petrol ecu is a non-lambda type. After some time thinking the problems were getting better, and some evidence (no more white smoke, no more coolant loss, no exhaust bubbles in the radiator) I became relaxed with the engine, and figured things were ok. Then the head gasket failed. So I pulled the heads off and found the head gaskets were fairly new looking, so I figure they went before I bought it and the heads were not skimmed when the gaskets were replaced.
So...
I am picking up the rebuilt heads on Friday (after a skim and bigger valve seats), I'll be lapping in new (big) valves and doing a little light porting when I get them back. With the fairly hefty skim I feel confident in using the composite type gaskets, and not torquing in the 4 outside bolts.
I will be removing the air conditioning compressor, and probably the viscous fan too. I'll rebuild it and see if it still pi$$€$ coolant into the sump and compression into the radiator , if not I'll be removing the exhaust which is a bit knackered and I am thinking of fitting a Rimmer Bros stainless steel sports system. Has anyone here got any experience with these systems? Are they worth the money? £510 seems reasonable with a lifetime warranty!
Cheers everyone!
Moses

mosesthemonk wrote:removing ----- probably the viscous fan too.

Hello Moses, Presumably, its function to be replaced or substituted by electric cooling fan(s)? It can seem an attractive proposition but it may upset the stability of your cooling system, so before you do, can I persuade you to read the Cooling Treaty in PDF format found Here: