recently bought a one-owner ’67 Chevy Impala with only 73,000
miles that’s in very good shape. I’ve started a work list for
spring that includes checking the antifreeze and transmission fluid
and changing the fluids that need changing. The 327 V-8 engine is
original and the owner left a note stating to add a lead additive if
using a lower octane gasoline, but if non-oxygenated gas is used, no
additive is needed. I filled it with non-oxygenated gas the day I
picked it up in mid-December. Is it OK to start and run it every few
weeks for the rest of winter?
off, congratulations on finding a true "survivor" from the
1960s. Very few of these vintage vehicles are still original,
unmolested and unrestored, which to my mind makes them even more
up some confusion here. Generally speaking, engines built before
about 1970 required tetraethyl lead in the gasoline to provide two
important requirements. First, lead was an inexpensive octane
enhancer to increase the octane level of gasoline for
higher-compression engines. Second, lead provided a heat-transfer
lubricating quality for valves. The lead helped transfer and
dissipate heat from valve heads to valve seats to prevent burned
valves. From about 1970 on, engines feature hardened valve seats and
stellite or sodium-filled exhaust valves to handle more heat,
negating the need for lead for this purpose. Today, tetraethyl lead
is banned from road use motor fuels due to its toxic nature.
engine in your ’67 Impala was built for leaded gasoline, there’s
likely more than enough lead buildup in this original engine to
protect valve seats — particularly in light-load conditions like
winter warm-ups and recreational driving. In fact, I wouldn’t
worry about the engine when using today’s unleaded fuels unless
you’re going to run the engine particularly hard. The correct
choice of gasoline for your vehicle would be premium non-oxygenated
to provide adequate octane as well as protect the fuel-system
components from degradation due to the alcohol content of
the information you and the rest of us driving older vehicles need.
Non-oxy gasoline is not a substitute for the lubricant quality of
leaded gasoline. There are legal fuel additives classified as "metallics"
that offer some of the heat-transfer capability of tetraethyl lead
that you can use to protect valves and valve seats on older engines.
Since the only
permanent "fix" for pre-1970s engines is to remove the
cylinder heads to install hardened valve seats and new valves, I’d
suggest driving the car until some type of symptom requires
disassembling the engine. Upgrade the valves and valve seats at that
Q: My son owns
a 2006 Mini Cooper. The muffler had a heat shield on it, which has
fallen off. The Mini service center stated it was nothing to worry
about. As a mother, I do worry about it. Should we be replacing the
A: On most
vehicles, the heat shield on the exhaust system protects the
catalytic converter, not the muffler. The reason is simple.
Temperatures inside the converter can reach well over 1,000 degrees
and the outside shell can reach 200 degrees or more. Mufflers
typically don’t get that hot.
shield protects the catalytic converter from coming into physical
contact with — and potentially igniting — leaves, newspaper and
other combustible materials. If the heat shield begins to rattle due
to broken mounts, it can sometimes be reattached or secured by
welding or steel straps. Once the shield is completely missing, the
only fix is to replace the catalytic converter — a potentially
If the missing
heat shield is part of or protects the muffler, I would be less
concerned. The repair, which would involve replacing the rear half
of the exhaust system, would be less costly.