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 Leaded gasoline boosted engine compression, reduced knocking, and
provided lubrication for valves and seats. An inexpensive octane booster,
anti-knock agent, and valve wear preventive, tetraethyl lead (TEL) also
fouled spark plugs, gummed up engines, and polluted the air via automobile
emissions. Today, most countries, including the United States, have banned TEL
from motor fuels. For the owners of classic cars, the end of leaded gasoline means
lead substitutes, alternative fuels, or engine overhauls.
Valve Jobs
and Unleaded Gas
As Jim Smart of the Auto
Enthusiast Weekly explains, "there's everything to be gained"
by overhauling your classic car's engine so that you can use regular unleaded gasoline.
Engine mechanics need to start with a plan, so Jim recommends "a blueprint
valve job that includes new valves, guides, hardened seats, value springs, and
Viton seals." The services of a competent machinist are essential, and all
valve jobs should begin with value guides that are in parallel. The right tools
for a valve job are important, too, and that's why we recommend a small-diameter flexible hone.
Valve
Guides and Bronze Inserts
As the slide show that accompanies Jim's article explains, valve
guide honing is a key part of the engine overhaul. Although some engine
builders replace their valve
guides altogether, others keep the factory originals by using bronze
inserts. Acting as a valve stem bearing, the bronze insert is driven into the factory
value guide. "Bronze inserts," Jim explains, "are an economical high-wear
answer to valve job life because they wear well and control oil flow to valve
stem". Measure the valve stem to the proper size, and then use a ball hone to improve
the surface finish, "like honing a cylinder bore for piston rings".
Flexible Honing for Valve Guides
Built
with a stiff metal steam and abrasive nylon filaments, the Flex-Hone
from Brush Research Manufacturing (BRM) is a cylinder
honing tool that features abrasive globules for a soft cutting action. Unlike
honing stones or other rigid hones, BRM's flexible hone produces a uniform
pattern of peaks and valleys for optimum oil retention. Users sometimes call our brush
tool by other names (including ball hone), but the results speak for
themselves. For valve jobs in classic car engines, we recommend using a small-diameter Flex-Hone.
Author's Note: This CR4 blog entry originally appeared in BRM's
Flex-Hone
Blog.
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Re: Valve Jobs in Classic Car Engines
