3.5 V8 Rough running > 80kms on LPG & replacement

[StuRR80]

Happy New Year all!

I recently had the Rangie tuned and the LPG working again. When doing the tune up, the specialist carb/gas mech said a cylinder on the left bank had low-ish compression and the spark plug was oiled. He said the engine would need a rebuild. Now, I don't have any money to play with for a rebuild but I do have a parts car with an engine which I was told was ok. What should I check to make sure I'm not replacing a slowly dying engine with an even more "dying" engine?!

Also, when running on LPG at speeds above 80kms, there's a miss or something which makes it run roughly, although not consistently. The mech said it was because the engine needed a rebuild (oil on spark plug, etc). I know LPG needs a "fatter" spark for run well on. It seems to run really well on petrol. I would assume the spark produced is always the same, no matter what speed?

I've replaced the battery (needed a new one anyway), the leads (although they're only Bosch, the mech said they were fine) and the coil (to a Bosch GT40).

I would have assumed the roughness would occur all the time, at all speeds but it's certainly only noticeable above 80 kph.

Any ideas?

Many thanks

Stu

[PhilipA]

Basically you should check the compression on any engine before fitting it.

Unfortunately there is also the issue of worn camshafts on rover v8s.

I take it the parts car does not run, seeing someone has told you that it is OK. So if i were you I would get it to run before going to the trouble of swapping engines. The whole car does not have to go, only the engine.
Regards Philip A

[bee utey]

Chemically and physically LPG is not petrol. The operational difference as far as you are concerned is the voltage required to ignite the mixture. It is higher on gas in a dual fuel engine unless the plug gap is reduced. Spark "fatness" is not a good criteria. Gap and voltage is.

The best answer for a points ignition is to reduce the spark plug gap to 0.6mm or 0.7mm. If it is an electronic ignition (fuel injection type) then the Bosch GT40 coil is incorrect and will not function correctly. Bosch BIC290 is recommended as a replacement. Your gap then should be 0.7 to 0.8mm

[101RRS]

I would run your engine on gas for a while and see if your plug is still dirty. Did your mech actually do a wet and dry compression test or just look at the plug.

I rebuilt a subaru 1800 engine and did something wrong and one of the clylinders ended up with lowish compression - never caused an issue and ran for another 250,000km before I sold the car. My point is I really would not worry about it at the moment - if it plays up later yes you will need to replace the engine but if it doesn't you have lost nothing.

Garry

[StuRR80]

Chemically and physically LPG is not petrol. The operational difference as far as you are concerned is the voltage required to ignite the mixture. It is higher on gas in a dual fuel engine unless the plug gap is reduced. Spark "fatness" is not a good criteria. Gap and voltage is.

The best answer for a points ignition is to reduce the spark plug gap to 0.6mm or 0.7mm. If it is an electronic ignition (fuel injection type) then the Bosch GT40 coil is incorrect and will not function correctly. Bosch BIC290 is recommended as a replacement. Your gap then should be 0.7 to 0.8mm

Sorry, I should have mentioned it's a twin-carb engine with an after-market Crane Fireball ignition.

I'll check the gap and reduce if required.

[StuRR80]

Basically you should check the compression on any engine before fitting it.

Unfortunately there is also the issue of worn camshafts on rover v8s.

I take it the parts car does not run, seeing someone has told you that it is OK. So if i were you I would get it to run before going to the trouble of swapping engines. The whole car does not have to go, only the engine.
Regards Philip A

The car does run but I've only managed to drive it onto and off the trailer. It doesn't currently have wheels, so I can't take it for a run around the farm to check how well it runs.

He mentioned the oil could be from the rings but he also said it could be coming through the valves from the heads? Is there a way to "easily" check which way the oil is moving?

[StuRR80]

I would run your engine on gas for a while and see if your plug is still dirty. Did your mech actually do a wet and dry compression test or just look at the plug.

I rebuilt a subaru 1800 engine and did something wrong and one of the clylinders ended up with lowish compression - never caused an issue and ran for another 250,000km before I sold the car. My point is I really would not worry about it at the moment - if it plays up later yes you will need to replace the engine but if it doesn't you have lost nothing.

Garry

He didn't say which tests he did, unfortunately. He did say it might last another 5 years but then it might only last another ????......!

[LoveMyV8County]

I wouldn't worry too much about low-ish compression unless it is very low.

What spark plugs are you using? I have had problems with ignition missing at certain speeds on other vehicles when the plugs are not the right ones. LPG burns hotter than petrol and the plugs need to be able to cope.

I use NGK Iridium ones on my LPG carby V8 with no problems.

Chris

[101RRS]

He did say it might last another 5 years but......!

Having low compression in one cylinder is probably not going to impact anything else and you probably won't notice the slight drop in performance - so as long as it still runs OK worry about it in 5 years.:)

[bee utey]

Having low compression in one cylinder is probably not going to impact anything else and you probably won't notice the slight drop in performance - so as long as it still runs OK worry about in 5 years.:)
Had low compression in one pot on my V8, when it got suddenly worse I popped out the piston to find a broken bottom ring and no top ring.:o. The engine builder had left out the top ring. Still ran OK just a bit uneven at idle.

Another tip with plugs, you should run plugs that are at least 1 heat range colder than stock, otherwise hot performance will suffer.

[StuRR80]

I wouldn't worry too much about low-ish compression unless it is very low.

What spark plugs are you using? I have had problems with ignition missing at certain speeds on other vehicles when the plugs are not the right ones. LPG burns hotter than petrol and the plugs need to be able to cope.

I use NGK Iridium ones on my LPG carby V8 with no problems.

Chris

I adjusted the gap tonight and took for a quick run. Gap was at 0.9mm, so I reduced to 0.6mm. I'll get a better test tomorrow driving to work but tonight it still seemed to be missing (maybe not so badly? Not sure yet will see tomorrow). At least it seems to idle better now (i.e. doesn't cut out!)

Seven of the plugs in it are NGK BPR6ES the other is NGK-R BPR6EY. The mech said he swapped one out (must have been that one). Not sure if that would make any difference? The plugs should only be appox 4000kms old (if that). Some did look sooty while a couple looked quite clean.

I also noticed that the resistor/ condensor/ or whatever it is (:angel:) i.e. a ceramic thingo with leads from the coil and somewhere else, moved around a bit which allowed one of the contacts to touch the mounting, which I'd imagine would earth it. Don't know if that makes any difference andI would have been doing it since I bought the car but I've zipped tied it into place anyway.

Cheers

Stu

[StuRR80]

Driving to work yesterday it ran a lot better and then I ran out of gas 1/2 way. Drove on petrol the rest of the way and filled up on the way home. Then it ran like a dog. I was lucky to get it about 90kph at times with the car jerking around. When I tried to floor it under 80kph it was under powered but there was no missing but when under load from 90 up it jerked and shuddered.

Then when I drive to work this morning, I start on gas and run the whole way. I bit of shuddereing here and there (still noticeable) but nothing like yesterday afternoon.

I just feel the mech wasn't too fussed to get to the bottom of the problem and decided the low comp was the issue....???

Is there anything else I can look at now, like timing, air restrictions, vaccuum, etc??

TIA

[bee utey]

Driving to work yesterday it ran a lot better and then I ran out of gas 1/2 way. Drove on petrol the rest of the way and filled up on the way home. Then it ran like a dog. I was lucky to get it about 90kph at times with the car jerking around. When I tried to floor it under 80kph it was under powered but there was no missing but when under load from 90 up it jerked and shuddered.

Then when I drive to work this morning, I start on gas and run the whole way. I bit of shuddereing here and there (still noticeable) but nothing like yesterday afternoon.

I just feel the mech wasn't too fussed to get to the bottom of the problem and decided the low comp was the issue....???

Is there anything else I can look at now, like timing, air restrictions, vaccuum, etc??

TIA
Sounds like poisoned plugs. They get a coating from running on petrol and this causes misfires. Not uncommon in my experience. My suggestion: new plugs, Bosch WR7DC or similar, run petrol only when the engine is completely hot and as little as possible, use premium unleaded when you do. Plugs should have white or light grey insulators when operating on gas. Any hint of yellow/brown and they are scrap.

[101RRS]

Just a little side track - in my dual fuel 3.5 running Bee Utey's holden dizzy and electronic amp at 9 BTDC and mainly on LPG - I am using NGK BP6HS.

These plugs are showing a nice light tan colour with no oil etc and the engine seems to be running OK. Are these plugs OK?

Also Bee Utey - I want to get another ignition amp like the one you sent me last year as a spare - where can I get one?

Cheers

Garry

[bee utey]

Just a little side track - in my dual fuel 3.5 running Bee Utey's holden dizzy and electronic amp at 9 BTDC and mainly on LPG - I am using NGK BP6HS.

These plugs are showing a nice light tan colour with no oil etc and the engine seems to be running OK. Are these plugs OK?

Also Bee Utey - I want to get another ignition amp like the one you sent me last year as a spare - where can I get one?

Cheers

Garry


Hi Garry
So long as the plugs are running well, stick with them. They are the correct heat range. IMO the problem with standard heat range plugs is they get hot enough to create a ceramic glaze of combustion products on the insulators, then they are stuffed.

As for your dissy amp, this was a genuine conversion kit marketed by Bosch in the 80's. My old (2000) Bosch catalogue lists a replacement module part number 9 220 066 005. Probably not available new any more. I know these are specific to the kits and are not interchangeable with other similar looking modules. The main advantage of this kit was easy reversal of the kit fitting to points, so all you need for emergencies is a standard Holden V8 rotor, points and condenser.

Another way to achieve spare parts is to remove the conversion and fit the innards of a Blue motor electronic dissy to your case. These were fitted to Holdens from 1981 to 1985 or thereabouts and are quite common on ebay.
Example: holden v8 electronic distributor (eBay item 250753048039 end time 16-Jan-11 23:04:59 AEDST) : Cars, Bikes, Boats (http://cgi.ebay.com.au/holden-v8-electronic-distributor-/250753048039?pt=AU_Car_Parts_Accessories&hash=item3a620bdde7)
Then with a remote coil/amp set-up like the one I use you have a modern system with OEM spare part availability.

Actually saw just what you want on ebay, I think. Ask the seller what the number in his amp/module is:
http://cgi.ebay.com.au/Commodore-EH-HR-GTR-Holden-Electronic-Distributor-Wgong-/110631762771?pt=AU_Car_Parts_Accessories&hash=item19c22abb53

And ask him to look inside the cap and post a pic of the rotor. The rotor won't be any use to you but the pick-up should be...

Cheers

[I Love My Landy!]

He mentioned the oil could be from the rings but he also said it could be coming through the valves from the heads? Is there a way to "easily" check which way the oil is moving?

G'day Stu,

To test if oil is entering the cylinder through a worn valve guide, drive down a long hill and use the gears to engine brake the car (i.e. have the engine running at high rpm with your foot off the throttle). At the bottom of the hill give the motor a rev and check to see if any blue smoke comes out of the exhaust. If there is a bloom of blue smoke then oil may be being sucked into a cylinder through a worn valve guide when the engine is running under high vacuum. A bloom of blue smoke may also be apparent after idling the engine for a moderate time (like when waiting for traffic lights).

A constant stream of blue smoke whilst accelerating may indicate oil getting past the piston rings.

Even if you are burning a little bit of oil through worn rings or through the valve guides it is not necessarily a major cause for alarm, unless it is excessive.

Edward

[StuRR80]

Sounds like poisoned plugs. They get a coating from running on petrol and this causes misfires. Not uncommon in my experience. My suggestion: new plugs, Bosch WR7DC or similar, run petrol only when the engine is completely hot and as little as possible, use premium unleaded when you do. Plugs should have white or light grey insulators when operating on gas. Any hint of yellow/brown and they are scrap.

Thank Bee Utey! I'll give it a whirl. I wish there was someone in Brisbane who knows as much about these things as you seem to! :D

If I'm running Premium unleaded, I'll need to get the timing adjusted to suit?

I have an RPI dual timing box which I need to fit hook up to the distributor so will need to re-time it then anyway. I've never done the timing before but I'm willing to give it a crack. I'll grab a timing light from Supercr@p or Repco or somewhere and give it a whirl one day. I'll need one for my 109" at some point, anyway.

[LoveMyV8County]

I also noticed that the resistor/ condensor/ or whatever it is (:angel:) i.e. a ceramic thingo with leads from the coil and somewhere else, moved around a bit which allowed one of the contacts to touch the mounting, which I'd imagine would earth it. Don't know if that makes any difference andI would have been doing it since I bought the car but I've zipped tied it into place anyway.


This is the ballast resistor, used to drop the voltage to the coil from 12v to 6v so that it is easier to start the vehicle while the starter motor is sucking juice from the battery. Both contacts would be live so yes, accidental earthing will not have been helpful.

Your coil should be one that is intended for use with a ballast resistor. Do you have a spare coil to swap over to see if it makes any difference?

While on the electrics, I would check that the connections to any solenoids on the LPG feed pipe and the mixer are good. Especially the one that switches out the petrol otherwise you will end up with a rough mixture.

What is your timing set at? LPG likes earlier ignition than petrol but prefers not to be advanced too much further again as the engine revs rise.

Also, I would keep the plug gap at 0.8 or 0.9 rather than closing it up. I used to use NGK BPR6ES but have never looked back after switching to BPR6EIX. LPG will reveal any inadequacies in an ignition system.

Lastly, are you satisfied the LPG running mixture is correct?

[StuRR80]

This is the ballast resistor, used to drop the voltage to the coil from 12v to 6v so that it is easier to start the vehicle while the starter motor is sucking juice from the battery. Both contacts would be live so yes, accidental earthing will not have been helpful.

Your coil should be one that is intended for use with a ballast resistor. Do you have a spare coil to swap over to see if it makes any difference?

While on the electrics, I would check that the connections to any solenoids on the LPG feed pipe and the mixer are good. Especially the one that switches out the petrol otherwise you will end up with a rough mixture.

What is your timing set at? LPG likes earlier ignition than petrol but prefers not to be advanced too much further again as the engine revs rise.

Also, I would keep the plug gap at 0.8 or 0.9 rather than closing it up. I used to use NGK BPR6ES but have never looked back after switching to BPR6EIX. LPG will reveal any inadequacies in an ignition system.

Lastly, are you satisfied the LPG running mixture is correct?


Ahhhhh! All these questions Chris....!! ;):p Unfortunalety, I'm not sure I can answer most of them though... :(

I just take it to someone who is "supposed" to know what they're doing and pay for the privilege! Although would prefer to know what to do and what to look for, myself.

I just had it tuned up (at least that's what I asked for) by a specialist carb & gas mech, so I "assume" he's set the mixture, timing, etc correctly (although everyone knows what "assume" did!)

I will check the Coil is supposed to work with a balast though and also the connections. With the amount of wire running in there, something may have come loose or just needs a clean.

You reminded me I did have an issue with a fuel solenoid cut-off a few months ago when I accidentally pulled the wire from the plastic casing. One of the guys at work tried to bodge a solder job to get it back on but maybe it's letting fuel through. I'll see if any petrol's excaping from there too.

Thanks for all the forthcoming help & tips guys :D

[bee utey]

Thank Bee Utey! I'll give it a whirl. I wish there was someone in Brisbane who knows as much about these things as you seem to! :D

If I'm running Premium unleaded, I'll need to get the timing adjusted to suit?

I have an RPI dual timing box which I need to fit hook up to the distributor so will need to re-time it then anyway. I've never done the timing before but I'm willing to give it a crack. I'll grab a timing light from Supercr@p or Repco or somewhere and give it a whirl one day. I'll need one for my 109" at some point, anyway.

I haven't run a dual timing box, generally I have found that dual fuel LR engines will run fine on LPG or premium unleaded at the same advance setting. The dual timing should be set up on a dyno or similar as the benefits would be highest right at the sweet spot for both fuels.

If your RR engine is standard you will be fine running between 6 and 10 degrees BTDC at idle. Test drive on both fuels, timing higher if it's sluggish on gas, lower if you detect pinging on petrol when under load and the engine is hot.

[101RRS]

As for your dissy amp, this was a genuine conversion kit marketed by Bosch in the 80's. My old (2000) Bosch catalogue lists a replacement module part number 9 220 066 005. Probably not available new any more. I know these are specific to the kits and are not interchangeable with other similar looking modules. The main advantage of this kit was easy reversal of the kit fitting to points, so all you need for emergencies is a standard Holden V8 rotor, points and condenser.

Another way to achieve spare parts is to remove the conversion and fit the innards of a Blue motor electronic dissy to your case. These were fitted to Holdens from 1981 to 1985 or thereabouts and are quite common on ebay.
Example: holden v8 electronic distributor (eBay item 250753048039 end time 16-Jan-11 23:04:59 AEDST) : Cars, Bikes, Boats (http://cgi.ebay.com.au/holden-v8-electronic-distributor-/250753048039?pt=AU_Car_Parts_Accessories&hash=item3a620bdde7)
Then with a remote coil/amp set-up like the one I use you have a modern system with OEM spare part availability.

Actually saw just what you want on ebay, I think. Ask the seller what the number in his amp/module is:
Commodore EH HR GTR Holden Electronic Distributor-Wgong (eBay item 110631762771 end time 14-Jan-11 22:08:34 AEDST) : Cars, Bikes, Boats (http://cgi.ebay.com.au/Commodore-EH-HR-GTR-Holden-Electronic-Distributor-Wgong-/110631762771?pt=AU_Car_Parts_Accessories&hash=item19c22abb53)

And ask him to look inside the cap and post a pic of the rotor. The rotor won't be any use to you but the pick-up should be...

Cheers

Thanks - great information - yep the backup of the points and condensor is a good safety measure.

[muddy]

A quick question have you smelt the exhaust on both gas and petrol to make sure that it is changing over ok and not flooding itself on either fuel?

Have been caught!!!!!!!!!!!

[StuRR80]

A quick question have you smelt the exhaust on both gas and petrol to make sure that it is changing over ok and not flooding itself on either fuel?

Have been caught!!!!!!!!!!!

That was one thought I had initially. I just need to work out how to tell if it's flooding (and no - not the rain!)..... :angel:

I can smell the LPG exhaust when the engine seems to be missing but assume that's the unburnt gas moving through - so I guess it could be either flooding or not being burned due to the previously suggested issues.

I bought some of the Bosch plugs as Bee Utey suggested, so will test on the run to work tomorrow.

[StuRR80]

Managed to get time to do some stuff on it today. Put the plugs in and took it for a run - ran like a dog! No power. Checked all the electrical contacts and the fuel cut-off. They were fine. Started stuffing around with the leads, etc and started pull ing them off one at a time to see if they made a difference. Found two that didn't change the running of the engine. OK. Checked leads were connected properly, put the old plug back into those cylinders, still nothing...... then it suddenly hit me! Yep, I'd switched the leads/cylinders..... so 2 hours later..... I'm afraid that's what you're dealing with people!

Anyway, changed them back and took it for a run and...... still missing :(

So can the next step be checking if too much gas it flowing through? How do I test that?

How would I tell if the mixture is right? I assume that is rich/lean? Is it just a matter of adjusting until it's right? That would then affect petrol though, which seem to run ok.

Also, it wouldn't be anything to do with distributor, etc? What, I wouldn't have a clue what but just throwing it out there!

Also, I checked the coil. It IS supposed to run with a resistor.

[bee utey]

You will have to find the main gas mixture valve/screw. It should be in the gas hose from the converter to the engine. I am not talking idle screws here. Start the engine, hold the throttle steady to around 2500 to 3000 rpm. Screw out the valve until the revs drop (going too rich). Screw it back in until you have maximum revs at a fixed throttle setting. Screw in some more, revs should drop. you are now running lean. Screw out until you just reach max revs. Then let it idle. Rev the engine quickly by hand and listen for quick clean run up to high revs. Adjust the main mixture 1/4 turn either direction either way and see if this slows down the revs. You are looking for the minimum amount of gas to get maximum rev-up rate. Then adjust the idle mixture for best idle speed. Test drive and see how it goes.

[StuRR80]

Thanks again Bee Utey :D

Will give that a whirl. I noticed the screws on the gas line up next to the carbies while scratching around this arvo. I guess the trick will be working out the optimum for each carb, since they have individual screws.

[LoveMyV8County]

Depending on your model of vapouriser, this article here may help

OMVL Adjustment - LandyWiki (http://www.landywiki.co.uk/index.php'title=OMVL_Adjustment)

I don't have an exhaust gas analyser, but was able to use the info here to get my system running pretty well.

Good luck.

Chris

[StuRR80]

Thanks guys for your help. I managed to get 1/2 hour to myself yesterday arvo to have a tinker. Twisted a couple of screws and took for a run. Runs much better thank you :D. I still need to spend a bit more time adjusting but it's got me past the shudders. Next thing will be to make sure he timing is right.

There's a couple of screws on the evaporator I'm not sure which is which though. I'll try to get a pic to explain better but one is backed by a spring (which I assume is idle adjust?), but I'm not sure what the other is for. The two fuel lines to the carbies have their own adjustment screws up near the carbies.