I hate to enter this discussion, but it is NOT advisable to put a catalytic
converter on a car that was not designed for it. The primary reason is that
without a mixture very close to stoichiometric, the catalytic converter will
overheat severely. This will render the converter useless after a short
while and potentially cause a fire if the converter has not been properly
heat shielded. Converters have been used on carburetted and fuel injected
cars, but regardless of the type of fuel system they require very tight
control of the mixture or (I repeat) they will self-destruct and cause a
fire hazard. I agree that there is little reason to remove a catalyst from
a "modern" vehicle originally equipped with it, but there is equally little
value in adding one to a vehicle not designed for it.
The fuel systems on most pre 1974 LBCs have nowhere near the mixture
control required to support a catalyst. In general, you will require an
oxygen sensor for feedback to get that good of mixture control. I
sympathize with the desire to pollute as little as possible, but start with
a good tuneup and make sure the rest of the engine is in good order. If
you're really intent on cleaning things up, Holley and others make
aftermarket fuel injection systems with oxygen sensors, but I don't know of
any that are designed to work in a sidedraft manifold. The best thing to do
is keep the engine in as good as tune as possible with the original fuel and
pollution control system. Another option is to retrofit an engine from a
newer vehicle. This is possible with Spitfires and TR-6s, but not too
practical with TR-4s.
One other point, any modification you make to an emission controlled vehicle
is technically illegal, unless it is CARB/EPA certified. This applies even
if the intent is to make the engine cleaner. I'd be happy to discuss this
off-list with anyone interested as I work as a design engineer for digital
electronic fuel systems, but we should stop this thread before anyone is
tempted to do something dangerous.
Ben Zwissler, zwissler@mail.hsonline.net
Columbus, Indiana
1980 TR-8
1966 TR-4A IRS OD
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