3.0.1 Engine block

The engine block is finished in a medium gray gloss enamel.

Two colors of gray were used during GPW production. The earlier color is a cold slate-gray while the later color is lighter and warmer.The date of the color change is not known at this time.

Cast markings: GPW 6015 in raised letters on lower-right side of block, with a script “f” above.

Early engines had a casting date code located on the lower rear corner of the right side of the block. This code included a single letter representing the month (i.e. A = January) and the numeric representation of the day. An additional digit may have represented the mold pattern number.

 

Around August, 1943, engine casting dates were relocated on the block. These date codes were located below the distributor and started with a letter representing the month followed by the day and the last digit of the year. For example H3311 was cast on August 3, 1943. The final two digits may indicate the mold or line number.

The serial number pad, located behind the oil filter is stamped with the engine serial number. The engines were stamped with their serial number when the blocks were machined, and the chassis were stamped with the engine’s serial number at the time the engine was mated to the frame. As a result, occasionally GPWs would roll off the assembly lines with a serial number that would appear to belong to a much older vehicle.

Around 12/42, the block casting or machining process was changed, resulting in a change to the serial number pad. At this point, the pad was no longer machined uniformly smooth from front to rear, but incorporated a “step” at the very rear of the pad.

Engines numbered 232051 through 243405 use studs NOT bolts to retain the valve covers. Use of bolts in these blocks will crack the cylinder wall bosses. Also, all spare engines with casting dates of K-10-4 to L-29-4 were changed to studs.*

The engine serial number should match chassis and data plate numbers. Non-matching serial numbers will result in a significant deduction of judging points.

* Per J.Gilmore archival research (!FoMoCo 12/44)

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3.0.2 Engine front mounting plate

The engine front mounting plate was changed sometime in early 1943* with the addition of a reinforcing plate on the generator side. This reinforcement was attached with ***three (3) rivets near the timing chain cover.

*“Ordinance Dept. report” described in AAW VII states that change was made 1/16/43.

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***Looking at several Front Plates, I think the CORRECT number of rivets for the reinforced LATE-style is FOUR, not the THREE as shown in the printed version of the Judging Standard above.

Chuck Lutz

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3.0.3 Valve cover and crankcase ventilation

The early road-draft crankcase vent system was used from start of production thru February, 1943. After this, positive crankcase ventilation was introduced, which resulted in changes to the oil filler tube, carburetor to air cleaner crossover tube, intake manifold and the addition of a PCV valve and plumbing.

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3.0.4 Cylinder head

Cylinder head markings include script “f” and 6050 near oil filter bracket.

The cylinder head is attached with 9 “f” Head bolts and 6 studs. The studs have a visible dome end and are painted along with the block. The head stud nuts, are heavy dimension and are S7 finished.

The center rear stud is longer then the rest, to accommodate the cylinder head to firewall ground strap. A second nut, along with two flat washers and a lock washer retain the cylinder head side of the strap.

The thermostat housing is marked GPW 8250 with a script “f”

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3.0.5 Oil pan and oil filler

Vehicles produced before a certain date in 1942 included an early style oil pan which used a cast drain boss, attached to the pan with three rivets and sealed with solder*. The oil pan is fastened to the engine block with recessed hex head integral-lockwasher bolts. The crankshaft pulley shield is fastened to the timing chain cover with four recessed hex head lockwasher bolts that also hold the front of the oil pan. Spacer rings are used between the shield and the pan to prevent interference. The threaded ends of the bolts should not extend too far past the timing cover flange. The pulley shield is properly marked with a script “f”.

 

Three styles of oil filler tube and dipstick were used during GPW production: A) The Very Early style (PN GPW-6763A) with narrow cap was used from start of production thru March ‘42. B) The Early style (GPW-6763B) with friction-fit funnel top was used from April ‘42 thru Dec ‘42. C) The late style (GPW-6763C) with crankcase vent and bayonet cap was introduced Feb. 8th 1943 and was used thru the end of production. **

The oil pump is marked GPW 6604 with a script “f”

* Have been unable to find any reference to change in oil pan. Date should be determined based on documentation or observation. ** Changeover date courtesy Jim Gilmore based on Ford archival research.

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 Part number for early style dipstick(B) should be GPW-6766B.(from NOS dipstick with Ford tag attached) -Todd Haley

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3.0.6 Manifolds

Markings: Exhaust GPW 9430 f , intake GPW 9425 f

PCV was introduced in February 1943* at which time the intake manifold was drilled and tapped for vent lines. Before February 1943 the intake manifold was not drilled and no bosses were present.

* “Willys-Ford teardown report” AAW#2, p213 states that Nov’42 GPW did not have tapped manifold.

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3.0.7 Carburetor

The correct GPW carburetor is a Carter model 539S also known as type W-O. The carburetor bowl, cover and horn are natural finished cast zinc (not gold).

The cast iron carburetor base is not drilled and tapped for a pipe plug as are the later civilian carburetor bases. The base is finished with a black chemical treatment similar to S2, it is dead flat with a white or gray tinge.The throttle shaft lever, throttle arm, rod, choke link, choke lever and all hardware are cad plated. The metering control rod is retained at the throttle arm with a bayonet-type washer and spring which is usually missing or replaced with an incorrect substitute. Most carb parts are marked with a Carter “C” logo and the Carter part number.

The carburetor is mounted to the intake manifold with two 3/8” hex jam (thin) nuts and split lockwashers, all S2 finished.

The carburetor linkage is painted gray with the exception of the return spring which is S2 finished.

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3.0.8 Oil filter and bracket

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