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    Re: 1984 bmw320i does it run on unleaded Archived Message

    Posted by Paul Howd on July 18, 2008, 9:21 am, in reply to "1984 bmw320i does it run on unleaded"

    As a rough rule any car with an alloy head (especially if the manufacturer was big in the US) should be ok on unleaded.

    Alloy heads are fitted with valve seat inserts which are useually hard enough for unleaded fuel.

    Cast iron heads have seats cut streight into the iron casting. This is not hard enough for unleaded and will gradually wear away causing the valves to recede into the head closing up the valve clearences However this is not as dramatic as it sounds. I have coverrd tens of thousands of mles in an old Land rover using unleaded with no noticable valve recesion the trick is to drive gently and keep the engine revs below 3000

    If you are not "sure" about an engines unleaded suitability regular checks of valve clearences will alert you to any problems.

    Older cars may need to have the ignition timing retarded unless you are going to use a "Super" unleaded.

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