Wide block vs Narrow block engine

Kdancy
Kdancy Senior Contributor
edited April 2014 in HUDSON
www.jalopyjournal.co/forum/forumdisplay.php?f=5

Flead from "the Hamb"-
NARROW BLOCK

Hudson introduced the Big six engine line in 1948 as a 262 cubic inch
only. Bore is 3.5625" and stroke is 4.375". This is the Narrow Block
engine and was produced as 262 cubic inch in 1948, 1949 and 1950. In
1950 a 232 cubic inch version was introduced for the Pacemaker line of
Hudsons. The 232 version has the same bore as the 262 but used a 3.875"
stroke crankshaft. Narrow block engines have different cylinder head
water passages and the lower oil pan rail is straight from the front
engine plate to the rear engine plate.

Engines made in 1948 and some 1949 used aluminum 2bbl intake manifolds.

All 232 versions used a 1bbl intake manifold. Cylinder heads were either
aluminum or cast iron and were unmarked in 1948 and 1949. In 1950 the
cylinder heads were marked next to the thermostat housing location "500"
for the 232 version and "501" for the 262 version.

Valve sizes are 1.8125" for the intake and 1.5625" for the exhaust.
These sizes remained as the standard valve size through the entire
production run from 1948 until 1956.

All engines received hand fitted pistons and bearings during production.
The information for the pistons was hand stamped into the block behind
the lifter and valve covers on the right hand side of the block. All of
these engines were assembled with the utmost care at the time of
manufacturing.

Crankshaft flywheel flange uses 7/16" bolts pressed into the crank with
nuts and a special lock plate. These have been an issue since day 1 of
this engine. The flywheels for both stick shifts and Hydra-matics must
be sealed to the crankshaft to prevent leaks with good high quality
Permatex #1 sealer.

These engines are suitable for stock and mild performance rebuilds but
not recommended for high performance usage. Cylinder heads and oil pans
do not interchange with the 1951 and later big six engines.



WIDE BLOCK

1951 saw the release of the Wide Block Hudson big six. With this came
the release of the 308 cubic inch Hornet engine. Cylinder head water
passages were improved and the block has a kick out for the longer
stroke crankshafts of the 308 cubic inch version.

Bore of the 308 is 3.8125" and the stroke is 4.500". The 232 and the 262
retained the same bore and stroke as previous years. The 308 version
also has stiffening ribs added to the lower area of the block about 2"
above the oil pan rail. Minor refinement was incorporated each year
until 1955. Valve relieve area was improved each year to increase air
flow over the cylinder.

All Hudson big six engines used 7/16" head bolts except for the 7X
racing engine built by the Hudson Race Shop. These 7X engines used 1/2"
head bolts for added head gasket retention. Details on the 7X engine
will be covered down later in the information.

Twin-H was made available in the 1952 Model year. It consisted of a
special cast iron intake, twin Carter 1bbl carburetors, two air
cleaners, special linkage and an exhaust manifold with two choke stove
pipes in the center two exhaust ports. Twin-H added 10 horsepower to the
standard 262 and 308 engines. It was not available for the 232 version.
The Twin-H was an assembly line option as well as being available as a
dealer add on item.

Aluminum cylinder heads were optional on all three engine displacements
during this time. Usually the aluminum head bumped the compression by .5
and gave a slight increase in horsepower. Head gasket retention with
the aluminum cylinder head has always been an issue so beware if buying a
used aluminum cylinder head.

Camshaft selection changed several times over these years. Two of the
performance camshafts Hudson used in most engines were the "742" and the
"040". Both of these camshafts started out as 7X racing camshafts and
are suitable for a daily driven Hudson. The "742" camshaft had the ramp
opening and closing rates altered in 1955-56 for use with hydraulic
lifters and work very well with mechanical lifter for street
performance.

The actual specifications for these two camshafts have never been
accurately listed except for the lift. The "742" has .354" valve lift
and the "040" has .390" valve lift. Both lift specs are at Zero lash.
New reground camshafts are still available that offer more performance
than these two so keep that in mind.



7X

The 7X engine was released sometime during the 1952-53 for racing and
severe usage. These were not assembly line installed but available for
installation at the dealerships or as a crate engine. These engines were
hand built and modified by the Hudson Race Shop on a very limited
basis.

It was only available as a 308 cubic inch version.

These 7X engines started out as hand selected block cores for
modifications. Each block was selected for the least core shift and the
thickest cylinder walls for durability.

Each engine received larger 2.00" intake and 1.6875" exhaust valves. The
valve ports and bowls were hand ported and opened to match the larger
valve sizes. The relief area was hand machined to remove any flow
restrictions over this area of the block into the cylinder.

The head bolt threads were enlarged to 1/2" diameter for better head
gasket retention. All 7X engines used a 232 cylinder head for higher
compression, 8.7 to 1 with the cast iron head and 9.2 to 1 for the
aluminum version.

Camshafts started out as the "742" camshaft and then progressed to the "040" camshaft sometime during the fall of 1953.

Each 7X engine received a Twin-H intake, carburetors and a special
exhaust manifold with a bolt on twin outlet elbow in place of the
standard single outlet elbow. The exhaust manifold itself is different
internally in the intake manifold heat chamber. The 7X version is
totally sealed off from the intake so no direct exhaust gas flows into
the intake. This offers a improvement in flow for the center two exhaust
ports.

Pistons, bearings and crankshafts were hand selected and fitted to these
7X engines for the best clearances and lowest amount of rotational
drag.

Horsepower ratings were never given as exact numbers due to the hand fitting and modifications but were listed as 210-220hp.



AMC years 1955 & 1956

Major modification were added in 1955. Hudson had already prepared to
make these changes for better durability. The only big still in
production was the 308. Both the 232 and 262 were dropped for the 1955
year.

Cylinder head bolt holes were enlarged to 1/2 for better gasket
retention. Cylinder heads were either the 308 cast iron and aluminum for
1955 and 308 cast iron but used the 262 cast iron in place of the 308
aluminum for higher compression in 1956.

The valve relieve area of the block was enlarged again for better air
flow. These blocks have the best out of the factory unmodified air flow
of all Hudson big six engines short of the 7X engine.

As stated above the lifters were changed at the end of the 1955 year to
hydraulic along with the reprofiled "742" camshaft due to problems with
adjusting the valves in the Nash chassis. A special slip-on fuel pump
eccentric was added to the arm that is 1/2 moon shaped to reduce
camshaft fuel pump wear.

Twin-H was still available for these two years. The intake changed to
incorporate the balance chamber so it was possible to adjust the
mechanical lifters in the Nash chassis. These intakes do not flow as
well as the 1954 and earlier versions. The exhaust manifold flange on
the intake was also changed so earlier intakes will not fit the 1955
& 1956 exhaust manifold.

The exhaust manifold takes a different elbow flange so the twin outlet elbow will not fit these manifolds.

The crankshaft flywheel flange is 1/2" shorter than the 1954 and earlier
engines and had 1/2" threaded holes for bolts now. This crankshaft is a
much stronger crankshaft and flywheel retention is no longer a problem
as with the earlier style. A modern neoprene seal is used at the rear
main location in place of the older rope seals.

Oil pans were changed to a center sump to clear the Nash chassis.

Thermostats housings take the modern style thermostats now as the bypass is blocked off with the mounting flange.


Comments

  • Kerry,
    Thanks.
    That's been one of my main references as I try to learn these Hudsons!
    I have found that info posted in a couple places.
  • SuperDave
    SuperDave Senior Contributor

    One comment on the above description.

      "the lower oil pan rail is straight from the front
    engine plate to the rear engine plate". 

    I'm not sure what is meant by that comment. Perhaps the writer was confused by the fact that the early sixes were straight.

      The oil pan (PN 300160) is the same on all big six engines , Therefor, interchangeable from 48 to 54.

  • Frankvintagefullflowcom
    Frankvintagefullflowcom Senior Contributor
    Ditto on the pans. All same for the pressure lubed sixes, exc. Jet.

    "..... block has a kick-out for the longer stroke crank". ?? Educate me on that one.
    The block width was increased to accommodate the larger bore 308 and, although it wasn't necessary, the additional width was carried over to all displacements. The Block deck height was identical for 232-262-308 and the rods were the same so the difference had to be taken up by the piston. That's why the 232 pistons look so funny. Pin-to-crown distance (commonly called "compression height") had to increase directly with the crank throw length, i.e., half of the stroke. 308 pistons are 1/16th shorter than a 262 in the Comp height dept. Now......find someone who cares. I can't.
    F
  • Frankvintagefullflowcom
    Frankvintagefullflowcom Senior Contributor
    I should have said "....change" instead of "increase". Depends on which way you are going.
  • BillUSN1
    BillUSN1 Member
    edited April 2014
    The crankshaft flywheel flange is 1/2" shorter than the 1954 and earlier
    engines and had 1/2" threaded holes for bolts now. This crankshaft is a
    much stronger crankshaft and flywheel retention is no longer a problem
    as with the earlier style. A modern neoprene seal is used at the rear
    main location in place of the older rope seals.
    Can someone define this a little more.
    I have the 49 262 and I'm getting a 54 308. Will it be a bolt in swap using the flywheel and clutch from the 262 on the 308 or will I need the manual trans flywheel for the 308? And then will the 10" clutch used with the overdrive trans bolt up or will I need to drill the flywheel to match, assuming the 308 may or may not have had a 10" clutch.
  • SuperDave
    SuperDave Senior Contributor
    All your stuff will bolt up. The above reference was about the 1955 and newer engine which was modified to fit into the Nash body and also used an enclosed driveshaft.. 48-54 are interchangeable. including the eight cylinder. The only compatibility problem is that HydraMatic can not be used on a 48-50 crank shaft. I am sure the 308 would have a 10 inch clutch.
  • Thanks Dave!
    I kind of read it that way but wanted to make sure.
  • IvarSweden
    IvarSweden Senior Contributor
    The engine/vin number doesn't match my 1948 Commodore Six but I've always assumed I have a 1950 narrow block 262. Reading this thread I think it might be a 1951 wide block 262. Can somebody say for sure?

    The casting date is 8-16-50
    VIN/engine number 10,000 something (way too low to be a late 1950?)
    The inlet manifold is cast iron
    The camshaft has part number 304078
    The oil pump gears are brass

    Does anybody have the block dimensional differences between wide and narrow?

  • Ric West IN
    Ric West IN Senior Contributor
    1st narrow block 262 casting ID number is 300001
    In late 1949, block was changed and ID number was 302627. This block was used for the 232 also.
    The wide block 232/262 casting ID number was 304299. which was used until late 1953.
    The 1954 232/262 block ID number was 310110.

    Hope this answers your question.

    "Ric"
  • Ric West IN
    Ric West IN Senior Contributor
    Just found your engine pictures on the other forum. Your engine is a very early wide block.

    The Foundry logo indicates this was cast at the Lakey Foundry in Muskegon Michigan.

    "Ric"
  • IvarSweden
    IvarSweden Senior Contributor
    Thank you, just what I needed to know. Luckily I haven't bought a new head gasket yet!

    image
This discussion has been closed.