Military-Vehicles: Re: [MV] VALVES AND UNLEADED FUEL???


Alan Bowes (
Fri, 10 Oct 1997 20:39:29 -0600

Winne, Jim wrote:

> Hi List!
> I have a question concerning the use of unleaded fuel in older engines that
> were designed for leaded fuel. I have been told by some that if you want to
> use unlead in these engines you will have to use an (expensive) octane
> booster additive or have the valves changed out in the engine. Not being
> very experienced at major engine work, I can honestly say that I don't have a
> clue. I figured that you guys could set me straight. I am about to have a
> valve job done (because of a burned exhaust
> Thanks all,
> Jim


As long as you're going to have a valve job done anyway, I'd suggest that you
either have the old seats induction hardened (if you can find a shop in your
area that has this capability), or else have hardened seats installed (a very
common procedure). You might also consider phosphor-bronze valve guides to
reduce friction, increase heat transfer from the valves, and reduce the
possibility of future valves sticking.

Good quality valves, new springs, seals, and keepers are also recommended. A
three-angle valve job will slightly reduce pumping losses (improve breathing).
You might also have the backs of the valves relieved a touch.

I suppose that you COULD add LEAD SUBSTITUTE to the gasoline (not to be
confused with typical "octane boosters" that are designed for a very different
purpose). There are a number of brands, including Red Line and STP. Again, if
you're doing a valve job anyway, have it done right and then you don't have to
worry about using lead substitutes.

I have a lot of other suggestions for improving the reliability and life
expectancy of engines without changing any of their basic design
specifications, but that's the subject of another discussion.


Alan Bowes
(Salt Lake City, Utah)

To unsubscribe from the mil-veh mailing list, send the single word
UNSUBSCRIBE in the body of a message to <>.