We have had the same problem with a few LandRovers It appeared that the expensive sparkplugs don't work on the V8 Try the cheap standard Champion plugs and a good quality standard lead set with standard amplifier and rotor and cap. On LPG renew these once a year and you should be fine.
Problem with carbs is that they wear the needles and seats within 8.000 km on LPG. After that running on petrol is poor.
Expensive bits are absolutely not needed when running on gas. And I know. I own a LandRover specialist garage in Holland. I have been converting, driving and maintaining RangeRovers on LPG for the last 15 years. Both carbs and injection. And LandRovers from the 109 V8 til the 2000 New RangeRover.
I notice a great miss of experience in the LPG fitters in the UK. Due to the new emissions regulations in Europe and the rest of the world new technically advanced LPG systems are invented every time. But here in Holland we drive on LPG for years. We started with oncontrolled systems. And they work fine. Maybe they use a little bit more gas than a fully controlled set. And maybe you loose a few horses. But compared to the price you have to pay and the problems you have with the fancy LPG kits it is not worth the extra money.
And the same with your friends 4.6. If he uses a plate mixer on top of his Holley carb, he is in trouble. The Holley is a very big carb. And that gives a very poor vacuum above the carb. In order to obtain a vacuum needed to get the gas flowing in the carb at low engine load it is neccesary to restrict the airflow to the carb. Problem with this is that at high engine load and RPM the flow is restricted too much and you loose a lot of power. Tell your friend to take the mixer off and try again on petrol.
"Steve Morgan" schreef in bericht news: snipped-for-privacy@demeter.uk.clara.net...
Here's a bit of a mystery.
>
> A friend and I both have V8s.
>
> This is mine:
>
> An '86 3.5 litre 110 with LPG, Strombergs (from a Rangie), RPI
> Advance-by-Retard ignition amplifier / standard ignition amplifier (they're
> on plugs-and-sockets so I can swap them around), Magnecor leads, Bosch
> 4-electrode plugs, etc. The engine was rebuilt (to standard spec) about 10K
> miles ago.
>
> This is my mate Bill's:
>
> An '89? fully rebuilt 4.6 litre 90 with LPG, Holley? 4-barrel with plate
> mixer for gas, pancake filter on the top, RPI cam, RPI Advance-by-Retard
> ignition amplifier, Magnecor leads (I think), and lots-and-lots of other
> expensive bits. You may have seen it in one of the mags (LROI?) a few months
> ago. It's bright yellow with a safety devices roll cage.
>
> Anyway, they both have a tendency to run like a dog and the symptoms are
> _so_ similar, we're convinced it's the same problem. Trouble is, neither of
> us has managed to find out what it is. Generally speaking, we reckon both of
> them are down on power. The main problem, though, is that when you're trying
> to get a wriggle on, all of a sudden there's a significant drop in power.
> Bill describes it as someone throwing a huge rubber band over the towball.
> There's a hill on the A5 between Shrewsbury and Telford. If it happens there
> (and it often does), it's a real struggle to climb - often to the point of
> having to change down to second and crawl up it at 25-30MPH. If it doesn't
> happen, we'll usually get up it at around 70MPH in fourth - though in the
> past I'd have no problem at over 80MPH in fifth. The problem is evident on
> both LPG and petrol, though it's _much_ more pronounced on petrol. With
> mine, if I'm running on petrol, it usually kicks in about 20 minutes after
> setting off. It ticks over fine, but there's no 'go'. It sounds as though
> it's missing, but I'm not convinced it is.
>
> Here's what we've tried:
>
> Engine wear: we've had mine apart, checked for anything obvious, put it all
> back together again with new gaskets and tested the compression. All looks > fine.
>
> Fuelling: Bill's tried two different carbs, plus a strange carb/injection
> hybrid. I've stuck with the Strombergs. Nothing's made a difference. >
> Ignition: I've replaced most ignition parts with higher-spec bits. The
> dizzy's been changed for an RPI recon. Recently, I rewired the ignition
> amplifiers so that I could have them both in and quickly switch between
> them. Nothing's made a difference, though as a general note, it's slightly
> stronger on petrol with the more advanced ignition (using the standard
> amplifier with the timing advanced for LPG) and there's no pinking. >
> Exhaust: Bill thought that it may be a restrictive exhaust problem, so he
> cut the brand new back box in half to take a look (!). Reckons it looks
> fine, so he's put it back together. Mine's a standard mild steel system. No
> apparent problems there.
>
> Bill's current thinking is that maybe the hydraulic lifters are pumping up,
> so he's considering trying solid lifters and adjustable tappets. >
> However, we're still really grasping at straws and we've been going around
> in circles like this for over around 2 years. Any insight would be greatly
> appreciated!
>
> --
> Smorgo (Steve Morgan)
> Hello: '01 VFR 800 FI, '86 V8 110
> Goodbye: '01 NT650V
> E-Mail address is spam-trapped. Use my first name at wormpurple dot com >
>
>
>
>