Lead replacement petrol has gone? the message is clear, look into the possibility of convert your engine/heads for unleaded petrol now. As far as the SD1 is concerned the V8 is the better option, as these seem to be the least affected when running on unleaded particularly 1980 on engines. Earlier heads may need a valve change? But even this will only cost around £100 and that is for both heads (see bottom of page) As for the others engine versions there are conversions for these if at a price? Perhaps this is the time to get in fashion and drop in a V8 as Rover have at last done this on the new MG!.

Unleaded petrol is available in 95 and 97 and now even higher octane's. The old Leaded 4 star petrol has been discontinued but may still be available in limited supplies in a few garages around the Country. The new fuel meets the old BS 4040 standard in respect to lead and octane rating, but has been improved to comply with the new EU regulations on pollution. The new fuel production will be limited to a total output of 100 million litres a year. If you really have to have leaded petrol

Lead additive suitable for adding to normal unleaded petrol is now on the market, This could be an answer for owner of older Vintage or Classics cars that are not suitable for cylinder head conversion or need a special brew?.

What other options are there?
What about LPG conversion? With the resent high costs of a barrel of oil and no signs of of a reversal of this trend this may now be the time to give this option even more though?There are DIY LPG kits on the market, prices start at around £400 for basic installation kit, to around £700 for a more complete kit offering better performance? LPG has not found favour with many owners though. In fact Ford and Vauxhall have stopped offering LPG version of their popular models due to lack of interest from the public at large, this is probably due to the high extra cost (between £1500 to £2000 extra) loss of the spare wheel or boot space? And the possibility of future price increases now maybe time for a rethink here also? (Diesel is now more expensive more that petrol) Some of those that have had LPG conversions have had problems some have been expensive to correct, also reports of poor starting and lack of performance particularly in winter. This in some cases is probably due to unsuitable conversions and or poor installations? LPG conversions come in many flavours; it is most important you chose the installation that is suitable for the engine/car it is to be fitted to.

Companies offering kits for Land and Range Rovers in particular the V8 carb and injection engines, these conversions should be suitable for the SD1 V8?. Other kits are available for 4 and 6 cylinder cars, they will come complete with instruction, but you will have to adapt them to suit your car and remember most of these engines do not have hardened seats or valves so valve recession will be problem.

Installing your own LPG system requires good working practices and some mechanical skills/tools, the gas pipe must not be connected at the tank or engine until the complete installation has been checked by an LPG installer, who will test and set everything up to suit your engine. So until this has been completed make sure you can switch over to petrol use.

Using LPG still works out at around half the cost of petrol (at the moment?) and produces almost zero emissions, the engine oil stays cleaner and plugs last longer and do not need frequent tuning? You also have the option via a dash switch, of switching to petrol if you are low on gas or need some extra poke! LPG offers similar performance to petrol but there are a few power trade off's, but LPG does offers a great deal less pollution, so is better for the environment! Remember LPG will involve loss of space somewhere even on larger vehicles, perhaps if manufacturers looked into building cars with sufficient space for the LPG tank would help? Some manufactures are no longer offering the option of LPG models due to lack of demand? maybe the recent hike in petrol prices will reverse this trend.

Availability of LPG? many more supermarkets and garage chains have now installed LPG filling equipment, but if the demand for LPG falls? it may becomes less viable keeping them!

RPI Engineering for complete installations including DIY (V8) links on this site.

Converting engines to use unleaded petrol
I think the best long-term solution? Your engine will then run on almost any fuel, including LPG this fuel also needs very hard valve seats. You will need some engine tuning changes, some engines are easy to convert as suitable head already exist, in due time there will be solutions to other engines, in the meantime continue using what you have decided suits you particular engine.

Which cars will run on unleaded? which engines will run without modification and what of those that will need some work? It now seems that even cast iron heads can have hardened seats fitted providing there is enough metal to take the new seats. As for those with suitable seats it is likely the valves will need replacing with a stelite or similar hardened valves, (Rover SD1 2300/2600, may only need the exhaust valves replacing) it would be wise to fit oilite type valve guides and later valve seals, more suited to unleaded fuel, this also goes for any rubber fuel pipes that may be fitted to some older cars.

will you suffer valve recession? It is unlikely that anyone will guarantee you will not suffer some valve recession? It would be wise to check and if necessary adjust the valve clearances before using unleaded and then recheck them at regular intervals, say after the first 1000 miles and depending on what you find longer intervals?

Important to keep engines in good tune; in some cases you will notice pinking (knocking) on acceleration or heavy load. If so you will have to retard the ignition a little (start at 2 deg) careful tuning will prevent further problems such as overheating. Remember you will suffer some loss of performance, on larger engines this may not be so noticeable?.

Rovers fitted with the later V8 engines (1980 on) have the larger valve seats i.e. the head casting is thicker, these may be suitable for unleaded use? Rover has declined to make any direct statement on this question possibly for legal reasons. Even so these head are fitted to Range Rover that do use unleaded fuel, although Rover say not under the same road conditions. 1980 was the year that the SD1 went to the USA where unleaded petrol was in use, so it may have been the reason for the larger harder valve seats i.e. production standardisation.

Rover say there is no suitable hardened seats for the earlier pre 1980 V8's, early SD1, P5B, P6 3500. Having said that it is known that all types of the Rover V8 engine have been and still are run on unleaded petrol (some with additives) in this country and around the world, as far as I know without any changes or problems? but I would advise a decoke and fitting the valve kit offered by PRi.

Whatever you decide to do will have to be your own decision? so the best of luck!
One good point if you do run into problems after using unleaded on unmodified V8 engines? you can retrofit later or modified heads or new V8 Range Rover 4.6 heads these are unleaded. They are interchangeable with earlier models of the V8, I have been using 4.6 heads for the last two 6 years without any problems.

4.6 cylinder heads have been designed to maintain the same compression ratio when fitting the thicker composite gaskets (these help to prevent gasket blowing problems due to the 3 row studs). Used with the normal tin gaskets would give an small increase in compression ratio over standard i.e. about 0.7? (9.35:1 to around 10:1)

Fitting composite head gaskets fit them dry, it is advised not to toque the outer 4 bolts as per the manual but to only 35 lbs, or you can leave them out? torque the rest as per manual. The outer bolt rows are the cause of head tilt and gasket failure. They are not even drilled on the later 4.6 heads.

Join a club that supports the model of car you have for further information on running your car on unleaded fuel. Many more companies now offer cylinder head conversions for almost any engine, see Classic and other car mags for more details.

---

Top of page