My Motor's manual Nash information on engine #'s goes up to 1955 and none have a 'Z' prefix for domestic US models. I believe that Packard supplied the big Nash/Hudson V8's.
1955 was the first year of the mighty 320 cu.in. Nash Ambassador and Hudson Hornet V8. The footnote says to refer to the Packard chapter for service information and sure enough the Packard 320 engine has the same bore (3 13/16") x stroke (3 1/2") matching the Ambassador and Hornet V8.
A larger 1955 Packard 352 cu.in. engine with a 4" bore x 3 1/2" stroke was used in the more premium Packard models. This larger 352 Packard engine may have been made available to Nash and Hudson in 1956.
1953 Packard engine #'s began with 'L'. 1954 Packard engine #'s began with 'M'. 1955 was the first year of the Packard OHV V8. Up until then, they had been straight 8's.
Could the numbering system have skewed all the way to 'Z' for the OHV?
Did Toronto have a foundry for Packard then? The main foundry was probably in metro Detroit. I know that Studebaker and Packard joined in 1954 and Studebakers were built in Hamilton, Ontario until 1966, but Packards never made it that far.
I'm interested on how you deciphered the engine number. Perhaps an AMC club or Packard club could help in IDing this engine?
Nice, rare Jensen by the way.
GEN-1 Nash/Hudson/Rambler V8s (1956-1966)
This engine family is now referred to as the "GEN-1" AMC V8, but in its time it was known as the Rambler V8. As part of a larger plan of merging
Packard,
Nash,
Hudson, and
Studebaker, AMC President
George W. Mason had a verbal agreement with
Packard that the two companies would supply parts for each other when practical. AMC started buying Packard V8s in 1954 for the big 1955
Nash Ambassador and
Hudson Hornet. These were supplied with Packard "Ultramatic" automatic transmissions - exclusively. Packard sent AMC some parts bids, but were rejected as too expensive.
George W. Romney, AMC's new head decided against further relationships with Packard.[sup]
[1][/sup]
Romney ordered his engineering department to develop an
in-house V8 as soon as possible. The engineering department hired David Potter, a former
Kaiser Motors engineer, to come in and help develop the engine. Potter had previously worked on a V8 design for Kaiser, and had the experience necessary to take the engine from drawing board to full production in just under 18 months, an extraordinary engineering feat at the time—
slide rules were the norm because there were no computers.
All these engines share common external dimensions, weight - about 601 lb (273 kg) - forged crankshaft and rods, as well as most other parts. The stroke for all GEN-1 V8 is 3.25 inches.
Engine displacement: The 250 cu in (4.1 L) has a 3.50-inch bore, 287 cu in (4.7 L) 3.75-inch, and the 327 cu in (5.4 L) a 4.0-inch bore. Bore size is cast on the top of the block near the back of the right bank cylinder head. This is difficult to see with the engine installed in a Rambler due to the close proximity of the heater. It can be done with a small inspection mirror. Like most V8 engine designs of the 1950s, the block features a deep skirt where the casting extends below the crankshaft centerline, forming a very rigid crankcase gallery. The oiling scheme is similar to the
Chevrolet Small-Block engine for feeding oil to the cam and crankshaft first, then to the lifter galleries.
