Quote:
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