Leaded / unleaded?

[jps]

Another novice question! I'm looking at donor Sierras (determined on this!) and obviously a lot of them date from the days of 4-star, when I was but a nipper. What are the implications for the fact that it's no longer available? Do people running these cars still use 'additives' / do they run them with unleaded but accept the performance deterioation / or did everyone get their cars converted to run on unleaded back in the late 80s or whenever it was that 4-star disappeared off our forecourts...?

[martinl]

It depends what you are using the car for. You can actually run a "leaded" head on unleaded providing you drive properly. To convert it to unleaded i don't think you need to do much more than either change valves or valve seats. If i bought a leaded engine, i would have it converted to unleaded while it was out of the car. Fords after 1989 are factory unleaded.

[Bonzo]

As far as I know, only the earlier Pinto engined Sierras are likely to used leaded petrol.

The CVH & 2 litre DOHC engines are fitted with unleaded heads.

I asked my local engine builder recently for a conversion cost, the price was just shy of £150.

His advice, " The old valve seats would be hard as hell due to the mileage " " If you are not going to be running up & down the motorways, you'll be unlikely to do the valve seats any harm "

That said, if it were my build & was going to fit an early Pinto engine, I would opt for a conversion.

[tkpm]

My pinto was leaded, whilst my engine was in bits i head the head skimmed and converted to unleaded for the cost of £50.

Terry

[jps]

Cool - sounds like this'll be a minor problem compared to the job as a whole!

Thanks for the feedback chaps!

[Spikehaus]

I think there is are 2 letters macined into the engine block on the offside exhaust manifold, mine was EN from memory. If you are going to buy your car you could use this as a check. I am sure twin knows the details for this, but was in the Haynes Manual

[robo]

Originally Posted by jps

Another novice question! I'm looking at donor Sierras (determined on this!) and obviously a lot of them date from the days of 4-star, when I was but a nipper. What are the implications for the fact that it's no longer available? Do people running these cars still use 'additives' / do they run them with unleaded but accept the performance deterioation / or did everyone get their cars converted to run on unleaded back in the late 80s or whenever it was that 4-star disappeared off our forecourts...?

Going back when god was a boy things like some of the early jags and rover v8 engines [p6] used to have 9.5/10.5 compression ratio and would only run properly on 5 star [100 octane], when 5 star was phased out they had to run the ignition retarded and richen up the mixture to stop them pinking.Some people tried running avgas but although it was 100 octane it was still unleaded or less leaded. Then 4 star was phased out most engines like these had to be changed to a lower compression version, in the rovers case the range rover lump was about by then and would run on the shite available at the pumps.Modern engines with fuel injection are back up to these higher compressions without an issue.The leaded/unleaded thing happened over a period of time and even though there was leaded fuels at the pumps the lead content was only at a fraction of what it was say 10 years before. The later engines that ran the last of the leaded were built to run on less lead which is why the dont suffer with valve recession like the really old stuff. Like bonzo pointed out seats harden with use so in limited mileage cars you will probably not have to worry but if your going by the book go for stainless exhaust valves and a set of hardened seats. F@@k me I must be old to remember all this crap.

Bob

[Bonzo]

Blooming heck Bob

The mention of 5 star petrol takes me back to my childhood.

Me dad used to send me up the garage for a gallon of 5 star petrol to put in the Mk7 Jaguar he was fixing up.
1s 10d per gallon seems to ring a bell !?

I am 57 so you must be very old mate

[robo]

I am not that far behind you Ronnie but I am not a grandad yet [I think] I did have a rover 3500s and that suffered on 4 star.

Bob

[baz-r]

the tetraethyl lead was put in petrol purely for the valves of 4 stroke engines it acts by preventing the heat of combustion burning/welding the metal of the head/valve to each other the sealing effect starts to break down and the valve ression starts.
a side effect of it added was to reduce the temp of self igntion of the fuel (higher octane rating) so engine designs to this into account

driving hard will increase this with lead free fuels but nothing will stop it
there are additives on the market but the best option is to find an engine thats designed to run on unleaded fuels as conversions (hardend seats) dont effect compression ratios etc and have to run retarded ign timings and are just not as efficent
the cost of addives that actualy work are expensive so a search for a cheap unleaded motor will pay of in the long run.