Jaguar XKE 4.2

Which brings us to October of 1964, when a 4.2-liter version of the 16-year-old XK six-cylinder engine was introduced in the Jaguar XKE.

The important change was in the cylinder block, which had been recast to allow a bore dimension of 92.07 mm, 5.07 larger than before. To get that much of an increase involved something of a lash-up.

1964 Jaguar XKE Series 2 front
A 4.2-liter six cylinder replaced the 3.8-liter in
1964 in the Jaguar XKE Series 2. Coverless
headlights soon followed.

Jaguar actually shifted the casting patterns to move the cylinders in relation to each other. Because the original engine had extra spacing between the middle two cylinders, numbers three and four, these were moved closer together; those at either end of the block, one and six, were moved farther apart. Overall block length was unchanged.

Oddly enough, the existing cylinder head worked just fine; the slight misaligning of four bores and their combustion chambers didn't seem to trouble either the engine or its makers.

The crankshaft itself was redesigned, but retained the original 106-mm stroke, so the new displacement was precisely 4,234.3 cc (258.4 cubic inches). This 12-percent increase in pumping capacity gave an 8.8-percent increase in torque, from 260 pounds/feet to 283, still peaking at 4,000 rpm.

Maximum horsepower held at 265 but was developed at 100 fewer rpm, 5,400. Curiously, that was 400 rpm into the new, more conservative red zone marked on the 4.2 car's tachometer.

Accompanying this engine were numerous other improvements, or at least changes. There were new rings on the new pistons to further cut oil consumption, a new starter motor, a radiator core changed from aluminum to copper, and an exhaust system newly "aluminized" for longer life.

A modern alternator ousted the old-fashioned generator, thus eliminating the gradual running-down of the battery in certain conditions, and the entire electrical system was switched to negative-ground.

Another new brake servo was installed. Thanks to new seals, the lube interval for the front ball joints was upped from 2,500 to fully 12,000 miles. At the rear, the suspension was altered slightly to prevent bottoming on severe bumps.

An external SU fuel pump supplanted the original in-tank Lucas unit. Replaceable-bulb headlights gave way to sealed-beam units (a concession to the American market, one suspects), though these remained "under glass" for the time being.

Nor was the cockpit overlooked. Seats were improved again, armrests were added to the doors, a between-seats "cubby box" was put on the transmission tunnel for stowing bric-a-brac, and dash trim went from high- to low-gloss (again in deference to the U.S.). External identification was far more subtle: just a small "4.2-liter" badge and covered hinges on the trunklid/rear hatch.

But of all the ameliorations made for the XKE 4.2, the one most acclaimed was an all-new gearbox with-at last-synchromesh on all forward gears. In conjunction with a new diaphragm-type clutch, the new four-speed was as nice to use as the old one was unpleasant.

If the XKE 4.2 was hard to distinguish visually from the 3.8 -- which remained in parallel production for a while -- driving it is a surprisingly different experience. Where the 3.8 feels and sounds like a traditional sports-car engine, somewhat raucous and becoming especially vigorous in the upper half of its rpm band, the 4.2 hardly seems like a piston engine at all.

Above slow-traffic revs, the familiar Jaguarish growl is replaced by more of a whine reminiscent of a gas turbine. And the 3.8's exciting shove-in-the-spine power step at about 3,500 rpm is not felt in the 4.2, which doesn't seem or sound that eager to rev. The power peak may be 5,400 on the dyno, but anything above 4,000 seems superfluous on the road.

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