Read this at http://www.grmotorsports.com/boneyard.html and thought the
rest of you could benefit from it too.
Triumph
The whole junkyard scene gets easy when you're dealing with a car that was
produced for as long as the Spitfire. Nearly 300,000 were produced from late
1962 to early '80.
The biggest changes were a body style change in 1971 and engine changes in
1967 (1296cc) and then '73 (1500cc). The engines are real easy to swap
around. Most racers like the 1296cc, while we really like the 1500cc engine
for autocrossing because of its greater torque. The 1976 1500 was the only
one to have 9.0:1 compression in 49 states. That's the one to have. The 1296
engine came with dual SU carbs. We like Webers, but the SUs work real well
when properly set up.
The next things to look for in a junkyard are transmissions and
bellhousings. The 1962-'64 cars had a "thin edge" alloy bellhousing which
will save about 20 pounds over the later steel bellhousings. The 1965 model
had the thick-edge alloy bellhousing, which is no heavier but even stronger
then the thin-edge piece. The best transmissions are the 1975-up single rail
close-ratio boxes. Unfortunately, they don't fit the early bellhousing, so
the best setup is probably a close-ratio box from any Triumph GT6, combined
with the 1965 alloy bellhousing.
In an effort to get back some performance, a 4.10:1 rear end ratio was
installed in 1972. While great for racing, this ratio will kill you on the
street (and in top speed contests) unless you use the overdrive
transmission.
Racers make the old-style (pre-1971) rear transverse spring work by
de-arching and stiffening the piece. This is great for autocrossing, but
lousy on the street. The first thing to do in any street-driven Spitfire is
to use the 1971-up revised rear spring. This spring pretty much solved the
rear end tuck-in problem so common to Spitfires. GT6 front springs with one
coil cut off work well on a Spitfire. GT6 brakes are considerably bigger
than those found on a Spitfire and are an easy, bolt-in swap.
The 1973-up cars have a larger front anti-roll bar (approximately 15/16 inch
instead of 11/16 inch) which, while not as good as a one-inch aftermarket
bar, is a cheap junkyard upgrade.
The later 1977-up cars have a smaller 13.5-inch steering wheel which makes
the car easier to steer. The last of the Spitfires also had five-inch-wide
wheels instead of 4.5-inch units. A better alternative is the 5.5-inch
wheels from the Triumph TR7. They bolt right on and are cheap.
The Spitfire weighed less than 1500 pounds when it was first introduced, but
the weight went up to over 1800 pounds by 1980. The biggest difference was
the addition of big, heavy bumper guards and later rubber bumpers.
The 1971-'73 style is the lightest, best-looking setup. The rear is bolt on,
the front takes a little massaging, but it's not that hard.
The biggest problem with the TR4 through 6 is just finding one in a
junkyard. If you do find a car, there are some things you should look for.
Obviously, it's very easy to put a six-cylinder TR6 motor into a TR4; it's a
bolt-in swap. The early six-cylinder engines (1968- 1970) offered the best
performance. The easiest way to find these engines, other than checking
serial numbers, is to look for a B stamped into the head.
The early A-type overdrive is the best transmission. Many dare not use these
units for competition, but the Triumph guys are making them work. The
better, large-piston O.D. has a freeze plug in the bottom. The later,
small-piston unit has a "bb" embedded in its case.
The later J-type tranny is better than nothing, but remember, you must
modify the rear tranny mount -and it's a big frame-altering job to put this
unit into an early, pre-1973 car. The TR4 and TR5 equipped with overdrive
came with a 4.11:1 rear end ratio.
The stock TR6 rear end ratio is 3.70:1. European fuel injection-equipped
cars had a 3.45:1 ratio.
TR4s came with optional competition front springs; try to find a set of
these. Datsun 240Z rear drums are lightweight, finned aluminum and fit
perfectly if you bore the centers. Datsun SRL 311 rear wheel cylinders will
move more of the braking to the rear of a TR6, which will help the car on
course. The 1974-up front calipers are of a better design and can be
substituted for the earlier units.
A lot of hard-to-find TR6 parts have common counterparts. A Dayco radiator
hose (#76431) will supply the lower and elbow hoses. A small-block Chevy
thermostat fits a TR6. A clutch from a Farmall tractor is essentially the
same as a TR6 unit. A Delco rear transmission bushing (# 299506) and seal (#
946940BX) are easier to find and cheaper than TR6 units. The differential
side seal is the same as an APAX #S5311. Caterpillar sells X-rayed main and
rod bolts at a fraction of the cost of TR6 prices.
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