|Cutaway head shows generous passages, valve sizes and integral seat and guides.||
this, it is interesting to note that, although the cams in all the Packard engines are, to all intents and purposes, identical, cast steel camshafts are specified for the engines supplied to Hudson and Nash. Even more interesting would be a comparison of the wearing qualities of the two different camshaft materials, after each has been subjected to long periods of operational service. But this we won't know for a while.
The cylinder head castings are made from the same material as the block. They are interchangeable, left to right, and each head weighs 64 pounds. Very generous water jacketing has been provided around the ports, valves, spark plugs and combustion chambers. Each head is located on the block by two dowels and is secured by 15 capscrews, 7/16 of an inch in diameter, in a pattern that surrounds each cylinder with five capscrews. Cylinder head gaskets are of the embossed steel type, .025 of an inch thick.
After playing with many different combustion chamber configurations, Packard chose the elliptically shaped, high turbulence "wedge" type chamber. Tests have shown that, at compression ratios of 12 to 1, this design provides a low burning rate of the fuel/air mixture charge and avoids a rapid pressure rise, thereby minimizing combustion roughness, and the chamber is quite insensitive to combustion chamber deposits usually incurred during low speed, light load operation. "Quench" and "squish" areas, formed by a .045 of an inch piston-to-cylinder head clearance, cover 20 per cent of the total piston area. Each combustion chamber is fully machined, which makes for a consistent compression ratio for all cylinders. The valve head diameters are unusually large for this type of combustion chamber, being 1 15/16
inches for the intake valves and 1 11/16 inches for the exhausts. This accounts for what appears to be a slight "shrouding" of the valves at the ends of the combustion chambers. The spark plug is located about 3/8 of an inch from the lateral axis of the cylinder bore toward the intake valve on the deep side of the chamber. Due to the angular location of the plug in the head, a counter-bored passage connects the firing end of the plug with the main combustion chamber cavity. The present compression ratio of the Clipper and Packard engines is a conservative 8 1/2 to 1, while the Hudson and Nash engines have an even more conservative ratio of 7.8 to 1. If one chose to use the heads of the 320-cubic inch Packard engine on the 352-cubic inch engine, a compression ratio of 9 1/4 to 1 would be obtained, which would be the upper limit for use with presently available gasolines. Or the heads may be milled .050 of an inch on the 352-cubic inch engine for the same result. The same amount milled from the heads of the Packard 320-cubic inch engine would result in a compression ratio of 9.1 to 1. To obtain a compression ratio of 7.8 to 1 on the Hudson and Nash, the heads from the 352-cubic inch engine are used. By milling the Hudson and Nash heads .065 of an inch, the compression ratio will be 8.7 to 1. When and if the heads are milled, each side-of the intake manifold should be milled the same amount as the heads to maintain correct intake port alignment. Also, the push rods should be shortened by the amount milled from the heads. As future fuels improve, it becomes a very simple matter of a coring and minor tooling change to increase the compression ratio of the Packard engine, which would undoubtedly be accomplished by lowering the "roof" of the wedge type chamber.
The alloy cast iron oil ring is of open slot design and measures 3/16 of an inch in width with a radial thickness of .166 of an inch, and uses a polygonally shaped light spring steel expander.
The hardenable alloy iron camshaft is driven by a one inch wide timing chain and sprockets on the crank- and camshafts. The cam is supported in the block by five removable steel-backed babbitt-coated bearings. The cam lobes are ground with a taper of six minutes and are positioned 1/16 of an inch in back of the valve lifter centers to avoid lifter overrun and insure positive lifter rotation. A helical gear, located ahead of the rear bearing journal, is an integral part of the camshaft and is used to drive the distributor.
Hydraulic valve lifters are used in all models, the bodies of which are Lubrite coated hardenable iron. The lifter faces are ground to a spherical radius of 30 inches and the lifter body diameter is .904 of an inch. Lubriting the lifters and phosphate coating the camshaft is said to minimize initial break-in wear, which seems to be the period when cam and lifter wear is the most severe. In line with
|Bottom of sturdy Packard V8 block has broached recesses for the positive location of the five main bearing caps.||Cylinder head capscrew pattern and the widely spaced bores provide a good gasket seal with minimum block distortion.|