[DeTomaso] Bronze or Steel Valve Guides

[JDeRyke at aol.com]

In a message dated 7/18/10 4:03:32 PM, cengles at cox.net writes:

> I am interested in learning aboutSteel vs. Brass (Bronze?) valve guides, 
> too.
> 
Real brass guides wouldn't last through a single Model T warm-up cycle, I'm 
afraid; too soft. 'Bronze' guides are usually phosphor-bronze, 
aluminum-bronze or silicon-bronze alloys.   It can wreck your day (and a few blades!) 
just trying to hacksaw a small piece of these materials--- very, very tough, 
hard and self-lubricating. I use phosphor-bronze for rack bushings. Often 
used for guides in aluminum heads to help counteract heat expansion, and they 
transfer heat better and faster than iron in performance engines. Some race 
engines use 'bronze' valve seats for the same reasons, but they don't stand 
up too long to the constant pounding from the valves.
If the shop gets a guide's shrink-fit or press-fit wrong in a head, the 
guide comes loose while the engine's hot & running and that act of the great 
game is instantly over. As for 'steel' guides, they are usually a type of cast 
iron. This works exceptionally well (especially in cast iron heads) because 
like a cylinder bore, the graphite in cast iron acts like a lubricant for 
alloy steel valve stems, fighting stem seizures. FWIW- J DeRyke