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6766Re: [classicrv] Re: New member and Questions

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  • Bill Combs
    Sep 3, 2001
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      > on 9/3/01 5:34 PM, bobalou1@...1@... wrote:

      > The lead was put into the gas to help keep the valves cool, I
      > think I seen a report that stated that it appears that there is no
      > apperant problems with running on unleaded. If anyone else has heard
      > this report please back me up.
      > Just my 2 cents worth, Bob.

      Conventional wisdom (you'll have to figure out how much credence you put in
      such) is that lead had two major jobs in gasoline:
      (1) increase octane, which really means limit pre-ignition and resulting
      turbulence and locally very high peak temperatures. Something to do with
      regulating the flamefront or such arcane notions.
      (2) mechanically cushion valve seats and valves, which take a mighty
      pounding pounding what with slamming shut thousands of times per minute.

      If the octane of the gas you use is high enough, you needn't worry about the
      first. Other types of smoke and mirrors have been used to increase octane.
      The second issue is more problematic. The common solution for the removal of
      lead (cushioning) was for engine manufacturers to strengthen (harden) the
      valves and valve seats. Older engines may or may not have valves and seats
      up to the challenge of operating without lead but can usually be
      retro-fitted with such when the heads are rebuilt. Consensus is that a lot
      of production engines were not built with such operation in mind and thus
      are not suited to that operation. The solution, if you have such a belief,
      is to add a commercial "re-leading" agent. If I remember correctly, they
      aren't really lead but have some other ingredient that has the same
      cushioning effect.

      I have an automobile with a 1967 Dodge 440 HP that has never seen lead,
      operating first only on Amoco Premium and then on what we all use now --
      with liberal use of octane booster in the last couple of decades. The valves
      are OK, but mileage is only 90,000. I use no re-lead additives. On the RV,
      on the other hand -- also a lead-era 440 -- I use a re-lead additive in one
      of her two tanks, the same one that feeds the (old) genset. I think of it as
      a precautionary measure.

      Bill Combs <ttursine@...>
      Stupidity got us into this mess
      ... why can't it get us out?
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