The 1955 Packard V-8 was new and modern. In that year the Clipper received the 320 CID version and the Packard’s displacement rose to 352.
In 1953 The Clipper received the 352 CID version and Packards had the new 374 CID piece.

So Great and Too Late

History –

The Packard OHV V-8, like much of what happened to the rest of the Company in postwar times, is a tale of what might have been. It was a great motor that even had some excellent racing successes, but it came too late to excite the horsepower-hungry crowd of the early 50s. As such, it was only used for two years. After the Company closed production in Detroit and moved to the Studebaker headquarters in South Bend, all of the Packard V-8 production ceased.

A large, powerful and modern V8 engine that might have lifted the dreary remaining Studebaker cars from their 60s doldrums flat disappeared, leaving Studebaker stuck with a measly 289 CID V8 to combat its competition’s 350-400 CID offerings. Stupid, really.

Packard V-8 Development –

In 1946 Packard instituted a program to explore the possibilities of new and novel engine designs suitable as successors to their venerable straight eight. Many unusual designs were tested and evaluated, including new manufacturing methods and new materials – even aluminum cylinder blocks.

By 1949, most of the details of what the new Packard engine would be, but there was still discussion what the displacement – which been originally set at 269 CID. Before laying out the design on paper, it became obvious that 269 cubic inches was going to be tiny, given the leaps and bounds which the Big Three manufacturers were increasing their engines’ displacement.

The concurrent rise in power and torque had Packard engineers reconsidering their original design. They recognized that they could not be caught flat-footed with an engine that would be under powered. Thus, Packard went to the other extreme – they designed a production engine with the potential for big displacement, with provisions for going even bigger whenever the need should arise.

Packard engineers had a history of never shying away from building engines of mammoth proportions – their straight eights, twelves and sixteen cylinder engines were “locomotives”, so it was no surprise that the 1955-1956 V8 was automatically a member of the “There Ain’t No Substitute for Cubic Inches” club. In 1955, a small” version of the V-8, at 320 CID, was installed in the mid-price Clipper Line (remember this is 1955 and Cadillac was at 331 CID, Lincoln at 341 CID and Chrysler at 354 CID so Packard’s idea of “small” was unique).

The 1955 Packard Line received a 352 CID version that had a 4.00″ x 3.5″ bore and stroke. which resulted what was considered a favorable stroke/bore ratio of 0.88 to 1. In 1956, the 320 CID engine was dropped, the 352 CID continued unchanged except for higher compression and was used in the Clipper Line. A 374 CID version was introduced for the Packard Line – with a bore and stroke of 4.125″ x 3.50″.

In 1955 AMC purchased the 320 CID version from Packard for Hudson and Nash high-line cars. Initial deliveries were detuned to deliver only 208 horsepower @ 4200 rpm and 300 ft. lbs. of torque @ 2300 RPM. After complaints by AMC, Packard delivered the 320 in the same tune as the Clipper (225 HP @ 4600 RPM and 325 ft. lbs. @ 2400). In 1956 Nash and Hudson received the 352 CID engine equipped with a 2-barrel carburetor rated at 220 horsepower @ 4600 RPM and 320 ft. lbs. of torque @ 2200 RPM.

Interestingly, Packard recorded their HP/Torque values more like what the DOT demanded in the 70s: the water, fuel and oil pumps were connected and operating; the generator was rotating but was not charging. Further, Packard adjusted the spark advance manually for best torque reading, not HP, and no open headers were allowed – dynamometer exhaust collectors were used. The intake manifold heat was blocked off and the fuel was 93 Octane Research gasoline. No fan or carburetor air cleaner were fitted. The dynamometer figures were corrected for a temperature of 68 degrees F at 29.92 inches of mercury. All this means that the advertised HP could have been much higher if then standard HP gathering procedures were used.

Even so, the big Packard had the edge on all competitors in all departments; the 352’s displacement was equal to or larger than its closest rival, the advertised power was 4% higher than their competition’s standard engines (Chrysler’s 300 and DeSoto’s Adventurer withstanding) and the advertised maximum torque was 2.9% more.

The engine weight of the Packard V-8 was for the most part lower than their competition – with all accessories except the air cleaner – it weighed in at 698 pounds.

Engine Details –

Block
The 210-pound cylinder block was cast from close-grained alloyed iron. The blocks for all engine sizes were identical except for the cylinder bore diameters though the bore cores were different – thus different part/casting numbers were assigned. The upper half of the bell housing was an integral part of the block, as was the common practice back then. In typical fashion, five transverse bulkheads separate the cylinders of each bank and are used as supports for both the crankshaft and the camshaft.

The Block in longitudinal cross section

 

The main bearing caps are located 0.25″ above the oil pan surface in longitudinally broached recesses. The cylinders are surrounded by full-length water jackets, except at the inboard sides, where the jacket length is reduced to make room for the valve lifter bosses and two oil galleries running the length of the block.

Thoughtfully, distortion of the cylinder bores was minimized by tying the cylinder head bolt bosses into cast vertical ribs. The center-to-center distance between adjacent cylinder bores is 5″ (large at the time (Chrysler FirePower Hemi engines only had a bore center distance of 4.5625″, considered huge at the time). This huge distance left a minimum of 7/8″ between bores on the 374 (1″ on the 352 and 1.1875″ on the 320).

This dimension also allowed the bore diameters to be enlarged substantially at a future date without changing the design or existing tooling – all that would have been required was a simple change in the coring of the cylinders.

Sufficient space in the underside of the block was provided for a substantial increase in crankshaft stroke, when the need arises, without interference with the existing block casting or other parts. The overall length of the cylinder block is 27.75″. The block was safely re-bored to 4.125″ in 1956 to deliver 374 CID with no danger from cylinder distortion or overheating using the 352 block castings. The 3.8125″ bores of the 320 CID blocks could have been bored to 3.9375″, but this was never done – Clippers merely received the 352 in 1956.

Crankshaft
Packard engineers spent considerable effort in evaluating forged versus cast crankshafts. According to their findings, a steel casting provided a sufficiently high level of elasticity as well as material density to effect a lighter crankshaft without sacrifices in rigidity or stiffness. And casting permitted the counterweights to be more favorably disposed for balancing effectiveness, as well as the coring of the crank pins to reduce the amount of unbalance and, consequently the size of the counterweights.

Thus, the finished Packard V8 crank was a heat-treated alloyed steel casting that weighed 56 pounds. The number 5 (rear) main bearing is the thrust bearing. The crankshaft was drilled to oil each of the two bearings on the crank pins.

The block in Cross Section

The five main bearing journals are ground to a diameter of 2.50″ and the crank pins are 2.25″ in diameter. With the 3.50″ stroke, an overlap of 0.625″ was between the crank pins and adjacent main bearing journals, and this contributed to the torsional stiffness of the crank.

The total connecting rod effective bearing area is 52.8 square inches and the total main bearing effective area is 38.6 square inches. A non-bonded rubber harmonic balancer was placed at the nose of the crank and was effective in reducing engine vibration. That balancer is integral with the crankshaft pulley assembly, and thus, would need to be replaced should either the pulley or the rubber fail or be damaged.

The main bearings and rod bearings were of the steel-backed replaceable insert type, used among all manufacturers at the time. As was also common, each connecting rod bearing was locked in the rod with a tab.

Connecting Rods
The connecting rods were drop forgings made from SAE 1041 steel and was the typical “H” section design. The connecting rods have a center-to-center length of 6.71875″. Two high tensile steel bolts were used to secure the rod cap to the rod. A groove was machined at the juncture of rod and cap to provide lubrication from the rod bearings to the cylinder walls on the opposite bank. Typically, balancing lugs were part of the rod assembly, one lug at each end, which could be machined to ensure that each rod weighed the same.

The engine used bronze piston pin bushings – pressed into the small eye of the connecting rod. It was bored to give .0002″ clearance between the bushing and the pin.

The connecting rod assembly had undergone very severe testing by Packard at all loads and engine speeds well in excess of those encountered that they considered any type of driving conditions. Each rod assembly weighs a hefty 26 ounces.

Pistons and Pins
Aluminum alloy “autothermic” pistons were used together with steel tension members to control the amount and direction of piston expansion. The used a “slipper” type skirt. Crown thickness of the flat-topped piston is .280″. Three ribs were designed to extend from the piston pin bosses to the crown for pin boss rigidity.

The .980″ diameter by 3.25″ piston pin is a full floating and was retained in the piston by snap rings. The pin was heat-treated SAE 1117 steel. The pin bores are offset 0.0625″ in the direction of the major thrust face. Pistons are tin plated to minimize “scuffing” during the initial break-in period. Piston weight is 22 ounces.

Two compression rings and one oil ring were used, set above the piston pin as is the usual practice. The alloy cast iron compression rings were 5/64″ wide with a radial thickness of .200″ and had tapered faces. The top ring was chrome plated to a thickness of from .004 to .007 of an inch for longer, life and freedom from the effects of high temperatures and corrosive gases. The alloy cast iron oil ring was of “open slot” design and measured 3/16″ in width with a radial thickness of .166″, and used a typical polygonally shaped spring steel expander.

Camshaft, Lifters and Rocker Arms
The hardened-alloy iron camshaft was driven by a 1″ wide timing chain. The cam was supported in the block by the standard type five removable steel-backed bearings. The cam lobes are positioned 0.0625″ in back of the valve lifter centers to avoid lifter overrun and are offset ground to insure lifter rotation.

Typical of the time, a helical gear was located ahead at the rear of the block and was used to drive the distributor. Cast steel camshafts are specified for the engines supplied to Hudson and Nash, though this was also changed shortly after introduction to the same specs as Packards. Hydraulic valve lifters were used in all models. The lifter body diameter is .904″. Shaft-mounted rockers were used on all models.

Cylinder Head
The cylinder head castings were cast from the same material and method as the block. They were interchangeable, left to right, and weighed 64 pounds. Generous water jacketing was provided around the ports, valves, spark plugs and combustion chambers. The head was located on the block by two dowels and was secured by 15 cap screws (bolts) that were 7/16″ (0.4375″) in diameter – with five cap screws to each cylinder. Cylinder head gaskets were the typical embossed steel type, 0.025″ thick.

While late to the party, Packard’s V-8 incorporated the best of many of it’s competitors. Packard waived the idea of a Hemispherical combustion chamber is lieu of the proven wedge and incorporated many of the ideas found in GM’s Cadillac.

Packard experimented with many different combustion chamber configurations during development, but chose an elliptically shaped, high turbulence “wedge” type chamber. Each combustion chamber is fully machined much like V-8 Pontiacs, which made for a consistent compression ratio for all cylinders. Tests showed that up to compression ratios of 12.0:1, the design provided resisted detonation and was not affected by combustion deposits. “Quench” and “squish” areas, formed by the 0.045″ piston-to-cylinder head clearance, covered 20% of the total piston area.

Valves
The valve head diameters were 1.9375″ for the intake and 1.6875″ for the exhausts. There was a slight “shrouding” of the valves at the ends of the combustion chambers.

Compression Ratios
The 1955 compression ratio of the Clipper and Packard engines was a conservative 8.5:1, while the original Hudson and Nash engines had 7.8:11, that was later corrected. By switching the heads of the 320 CID Packard engine on the 352 engine, a compression ratio of 9.25:1 could be obtained. Or the heads on the 352 could be milled .050″for the same result. The same amount milled from the heads of the Packard 320 engine would have resulted in a compression ratio of 9.1:1.

To obtain the compression ratio of 7.8 to 1 on the Hudson and Nash, the heads from the 352 engine were used. By milling the Hudson and Nash heads .065″, the compression ratio would be 8.7:1. When the heads were milled, each side-of the intake manifold had to be milled the same amount as the heads to maintain correct intake port alignment. Also, it was recommended that the push rods should be shortened by the amount milled from the heads to avoid lifter pump-up. For 1956, the 352 CID and 374 CID head compression ratio was increased to 9.5 and 10:1 respectively with a new cylinder head that yielded these rations by fitment on either the 352 or 374 CID engines.

Spark Plug Location
The spark plug was located about 0.375″ away from the center of the cylinder bore, toward the intake valve, and on the deep side of the chamber.

Packard V8 Engine Use by Vehicle –

1955:

    • 320 CID V-8: Fitted to Clipper DeLuxe and Super, as well as Nash and Hudson. Overhead valves. Cast iron block. Displacement: 320 cid. Bore and stroke: 3.8125″ x 3.5″. Compression ratio: 8.1:1. Horsepower: 225 @ 4600 RPM. Torque 325 ft. lbs. @ 2400. Carburetor: Carter Type WCFB four-barrel Model 2232S with cylinder head No. 440689; Model 2284S with cylinder head No. 440854.
    • 352 CID V-8: Fitted to Clipper Custom. Overhead valves. Cast iron block. Displacement: 352 CID. Bore and stroke: 4.00″ x 3.5″. Compression ratio: 8.5:1. Horsepower: 245 @ 4600 RPM. Torque: 355 ft. lbs. @ 2400. Carburetor: Carter Type WCFB four-barrel Models 2232S or 2284S.
    • 352 CID V-8: Fitted to Packard Patrician and Four Hundred. Overhead valves. Cast iron block. Displacement: 352 CID. Bore and stroke: 4.00″ x 3.5″. Compression ratio: 8.5:1. Horsepower: 260 @ 4600 RPM. Torque: 355 ft. lbs. @ 2400. Carburetor: Rochester 4GC four-barrel Model 440823.
    • 352 CID V-8: Fitted to Packard Caribbean. Overhead valves. Cast iron block. Displacement: 352 cubic inches. Bore and stroke: 4.00″ x 3.5″. Compression ratio: 8.5:1. Horsepower: 275 @ 4800 RPM. Torque: 355 ft. lbs. @ 2400. Carburetor: Two Rochester Type 4GC four-barrel carburetors fitted as follows: (front) Model 476010; (rear) Model 476011.

1956:

    • 352 CID V-8: Fitted to Clipper DeLuxe, Super and AMC Nash and Hudson. Overhead valve. Cast iron block. Displacement: 352 cid. Bore and stroke: 4.00″ x 3.5″. Compression ratio: 9.5:1. Horsepower: 240 at 4600 RPM (220 HP in Nash & Hudson). Torque: 350 ft. lbs. @ 2800 (320 in Nash & Hudson). Carburetor: Carter Type WGD two-barrel Model 2393S.
    • 352 CID V-8: Fitted to Clipper Custom, Executive and Studebaker Golden Hawk. Overhead valve. Cast iron block. Displacement: 352 cid. Bore and stroke: 4.00″ x 3.5″. Compression ratio: 9.5:1. Horsepower: 275 at 4600 RPM. Torque: 380 ft. lbs. @ 2800. Carburetor: Rochester Type 4GC four-barrel carburetor Model 6480253.
    • 374 CID V-8: Fitted to Packard Four Hundred and Patrician. Overhead valves. Cast iron block. Displacement: 374 cubic inches. Bore and stroke: 4.125″ x 3.5″. Compression ratio: 10.0:0. Horsepower: 290 @ 4600 R.P.M. Torque: 405 ft. lbs. @ 2800. Carburetor: Rochester Type 4GC four-barrel Model 6480253.
    • 374 CID V-8: Fitted to Packard Caribbean. Overhead valves. Cast iron block. Displacement: 374 cubic inches. Bore and stroke: 4.125″ x 3.5″. Compression ratio: 10.0:0. Horsepower: 310 @ 4600 R.P.M. Torque: 405 ft. lbs. @ 2800. Carburetor: Two Rochester Type 4GC four-barrel carburetors fitted as follows: (front) Model 6489090; (rear) Model 6489091.

Here is a 1956 Studebaker Ad touting the 352 CID Packard V-8

 

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