Re: [Amc-list] leaded gas WHOA guess I won't be doing this any more

[Jim Blair <carnuck@xxxxxxxxxxx>]

I have seen a lot of engines with the valves burnt after the first unleaded gas came out. Most modern fuels have a built in additive to prevent this now. Marvel Mystery oil helps in some older engines too. Just don't use it (or 2 stroke oil) in engines with an O2 sensor (It can be an expensive mistake!)

Jim Blair, Lynnwood, WA '87 Comanche, '83 Jeep J10, '84 Jeep J10
From: "Bruce Hevner" 
Subject: [Amc-list] leaded gas WHOA guess I won't be doing this any
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>I have never seen any evidence that this part, below, is true:
 
> "Lead also acts as a lubricant, thus lead substitutes can be helpful 
>in pre-1973 engines that do not have hardened exhaust valve seats; a 
>lead substitute will help the seat from wearing excessively. "
 
>This idea has been parroted since the day no-lead and low-lead gas was 
>introduced; it was a big fear, reasonable at the time, but as far as I 
>can see, proven insignificant.
 
WHOA!!!
I can tell you from experience that it's CERTAINLY true!!
 
HOWEVER,, there have been some exceptions that have showed up after years of
taking apart street and race motors run on leaded and unleaded fuel.
 
You MIGHT be able to get away with running unleaded in a pre-unleaded motor
IF,,,
It's run in a light vehicle and not run at high rpm or under a heavy load.
THAT'S where the exh valve seat problem shows up. I have seen truck engines
with exh seats eroded so far down into the head that it bottoms out the
lifter causing the engine to skip !!! It has also been observed that once an
engine has been run on leaded fuel for a period of time the lead imbeds
itself into the head and will continue to protect the seat (although at a
reduced level and as long as the seat is not re ground) after switching to
unleaded. I recommend to all my customers with early heads that hard seats
be installed when doing valve work.
 
At the same time the switch was being made from leaded to unleaded fuel the
switch was ALSO being made to hard exh seats and better valves.
 
Be careful of the lead additives. Many of them contain nothing more than a
synthetic additive that's SUPPOSED to lubricate seats. This one is the real
deal,, http://www.realleadinstead.com/
 
But HEY,,, that's just ME!!!
Bruce Hevner
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