BY THOMAS A. DeMAURO • ARTWORK COURTESY OF THE AUTOMOTIVE HISTORY PRESERVATION SOCIETYPackard
Powerhouse
Fastidiously engineered for
1955, Packard’s fi rst OHV V-8
was introduced too late to help
save the company
P
ackard was rather late to the overhead-valve V-8 launch
party with the debut of its 352- and 320-cu.in. engines for
the 1955 model year. Though its history was steeped in prior
engineering achievements, including the famed V-12 Twin
Six four decades earlier and others since, Cadillac and Oldsmobile
had already released their versions of the OHV V-8 for 1949. Then
Chrysler, Studebaker, Lincoln, De Soto, Dodge, Buick, Ford, and
Mercury all came to market with their designs before Packard did.
If that wasn’t enough, the introduction would also have to
share the press limelight with newly arriving OHV V-8s from
Chevrolet, Pontiac, and Plymouth. And let’s not forget that
Packard’s purchase of Studebaker in October of 1954, which
formed the Studebaker-Packard Corporation, would also bring
signifi cant change.
According to the S.A.E. paper, “The New Packard V-8 Engine”
by W.E. Schwieder, development began “shortly after World War
II,” and by the Fall of 1949 the OHV 90-degree V-8 confi guration
was selected. A long-term plan was developed. “Instead of being
concerned about designing to meet minimum requirements, the
contrary approach was taken to ensure that changing requirements
could be satisfi ed without major retooling,” Schwieder stated.
It was determined that an oversquare (large-bore/short-stroke)
design OHV V-8 would provide better mechanical and thermal
effi ciency than the undersquare (small-bore/long-stroke) outgoing
L-head straight-eights—the 212-hp 359-cu.in. version being the
largest and most powerful. And the valve-in-head layout would
improve volumetric effi ciency. Accordingly, higher output could be
achieved while also increasing fuel economy.
Among the factors that governed the size and weight of the
engine were providing for future displacement increases and higher
compression ratios, a straightforward design approach to allow for
effi cient manufacturing and assembly, and setting “a new standard”
for durability.
The “high-grade alloy iron” 4.00-inch bore cylinder block
featured wide 5-inch bore spacing for future growth. Five bulkheads
added rigidity and supported the camshaft and crankshaft. Testing
had determined that extending the block below the centerline of the
crankshaft wasn’t necessary. Large full-length water jackets around thecylinders provided better cooling, and the upper bellhousing was
cast integral with the block to reduce defl ection in the driveline.
Following evaluations of crankshaft types, cast steel was
chosen over forged steel, as it was deemed suffi ciently strong, it
saved weight, the counterweights could be optimally positioned,
and balancing was easier. Its stroke was 3.5 inches, main bearing
journals measured 2.499 inches, and the connecting rod journals
2.25 inches. The crankshaft was supported by two-bolt main
bearing caps.
Drop-forged steel I-beam connecting rods attached to auto-
thermic, aluminum alloy, slipper-type, fl at-top pistons via full-
fl oating pins. The pistons featured steel struts to control expansion
and were fi tted with alloy iron rings—chrome-plated top com-
pression ring, Ferrox-coated second compression ring, and an
open-slot, ventilated oil ring.
The hydraulic-lifter camshaft had 250 degrees of advertised
duration and .375-inch lift on both the intake and exhaust.
Cylinder heads were retained by 15 bolts. The ports were
described as “equal in cross-section throughout, possessing
generous radii at all junctions, and are contoured to minimize
restriction, control fl ow, and provide optimum turbulence as the
charge enters the combustion chamber.” Intake port openings were
rectangular, and on the exhaust side, the center ports were paired
and shared the same outlet to the cast-iron exhaust manifolds.
The large valves measured 1.937-inch intake and 1.687-inch
exhaust, and were in integral valve guides, which reduced their
operating temperatures. Single valve springs, shaft-mounted
1.60:1-ratio iron rocker arms, and^3 ⁄ 8 -inch diameter steel tube
pushrods were employed. Valve covers had seven fasteners to
reduce the chance of oil seepage.
According to Packard, the machined, high turbulence,
“elliptically shaped,” wedge-type combustion chamber was
ultimately chosen due to its favorable burn characteristics and
adaptability for increasing compression ratios in the future. Though
compression ratios up to 12:1 were evaluated in test engines, a
conservative 8.5:1 was chosen based on the quality of the fuel
available to the public and to ensure suitable operation even when
chamber deposits were present.34 HEMMINGS CLASSIC CAR OCTOBER 2019 I Hemmings.com