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IT's NO BIG secret that in a head-to-head performance match between a V-6 Capri and a Mustang II with the same
engine, the, Mustang is the loser-and by a lot. Place identical engines in two identical cars but load one with
650 lb of ballast and in any test of acceleration the lighter car is going to win every time. That in essence
is the millstone hanging around the V-6 Mustang II's neck; it's solid, well built, quiet, plush-and heavy.
What to do? Well, if you're an unhappy Mustang II owner you could replace all the V-6 emblems with 4-cylinder
stickers and save yourself the embarrassment of explaining why your car is so slow. Or you could trade in your
1974 Mustang on a 1975 with the 302 V-8. This is not only a very expensive alternative (in first cost and fuel
consumption), but initially the 302 will be available only with an automatic transmission.
What's the solution to this dilemma? One is turbocharging, or specifically the turbocharged V-6 Mustang II
from Spearco Performance Products, Inc, 2054 Broadway, Santa Monina, Calif. 90404 (213 828-9552). George Spears,
the man behind Spearco, has engineered a complete turbocharging kit for the Mustang II with V-6 and 4-speed
transmission. The kit features a Rajay turbocharger and was designed to be a bolt-on installation; no welding
is required, nor is it necessary to relocate the battery or battery box. Because the Mustang engine compartment
is extremely crowded and space is limited with the turbo installation, Spears recommends that the kit be installed
by an experienced mechanic with tools for working in confined quarters. Installation time under these conditions
is approximately 10 hours; someone less familiar with mechanical things
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will need more time.
The Spearco kit (which costs $625) doesn't compromise the car or the engine the way some turbocharger
installations do. It's designed to fit Mustangs with all the power equipment, such as factory air conditioning
and power steering and brakes. In addition the kit is fully compatible with all emission control systems,
including exhaust-gas recirculation, Thermactor air-injection piping and even the vacuum retard system. A few
words of caution, however. Although turbocharging doesn't necessarily increase exhaust emissions and when done
right can even help, it falls into the category of illegal engine modifications in some areas of the country,
including Spears' own home state California. Spears and other turbocharger manufacturers such as Crown are
currently having their kits tested by the California Air Resources Board in an attempt to gain an exemption
from the prohibited modification list, but we suggest you check local regulations before proceeding with a
turbo installation.
Spears' turbocharger design eliminates the complication of a wastegate or a pop-off valve for limiting
boost pressure: the dual exhaust piping has been designed and sized so that with the removal of the stock
muffler the exhaust system provides sufficient back pressure to limit boost to approximately 10 psi. The
two stock resonators are retained, and these in conjunction with the muffling effect of the turbocharger
quiet the engine. We found, however, that at a steady 50. and 70 mph the modified car is 3 dBA louder inside
than the stock version,
Modifications to the engine to take the stresses and strains of turbocharging are few. Jet sizes have
been increased slightly,
from 0.056 to 0.0605 in. for the primary and from 0.071 to
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| Road & Track | January 1975 |
MustangII.Org
