Flathead V8 Engine Specifications
221 & 239 Cubic Inch - 24 Stud

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Middle Years V8: 1938 to 1948

1946-48 (59A style) pictured above

In 1938 Ford made new changes to the flathead V8, the most obvious change being the use of 24 studs per head instead of 21 as previously used. The engine underwent various other changes as years passed.

In 1939 when the Mercury car line was introduced, the engine's cylinder bore was opened up for a larger displacement in the Mercury car. Changes to the distributor occurred in 1942 and again in 1946.

The cooling fan was driven by its own v-belt beginning with 1942 models. The engine continued to be cast with the upper bell housing integral with the cylinder block assembly. In the post-war production both Ford and Mercury versions had the larger bore (3-3/16").

Water outlets were in the top center of each cylinder head for all 1938 to 48 motors. Water pumps were mounted in the lower front corners of all blocks from this era, and doubled as the front motor mounting pad.

 

Year Displacement
(Cubic Inches)
Bore & Stroke
(Inches)
Maximum Brake HP Compression Head Studs Notes
1938 Ford 221 3.0625 x 3.750  85 6.20:1 24 1,4
1939 Ford 221 3.0625 x 3.750  85 6.20:1 24 1,4
1939 Mercury 239 3.1875 x 3.750  95 6.30:1 24 1,4
1940 Ford 221 3.0625 x 3.750  85 6.20:1 24 1,4
1940 Mercury 239 3.1875 x 3.750  95 6.30:1 24 1,4
1941 Ford 221 3.0625 x 3.750  90 6.20:1 24 1,4
1941 Mercury 239 3.1875 x 3.750 100 6.60:1 24 1,4
1942 Ford 221 3.0625 x 3.750  90 6.20:1 24 2,4,6
1942 Mercury 239 3.1875 x 3.750 100 6.60:1 24 2,4,6
1946 Ford/Mercury 239 3.1875 x 3.750 100 6.75:1 24 3,5,6
1947 Ford/Mercury 239 3.1875 x 3.750 100 6.75:1 24 3,5,6
1948 Ford/Mercury 239 3.1875 x 3.750 100 6.75:1 24 3,5,6

Notes:
1) Used the "Eggshell" or "Diver's Helmet" style pre-war distributor (1932 thru 1941)
2) Used the "Crab" or "Pancake" style distributor (1942 thru 1945 engines).
3) Used the postwar style (1946 thru 1948) round distributor (similar to the crab style) with two bundled wire harnesses off the cap.
4) Prewar "81A" and wartime "41A" style blocks.
5) Postwar "59A" style blocks. These had the "59" cast into the top of the bell housing. Note that some of the 59A style blocks were also sold as replacement engines for pre-war 221 cubic inch cars and had the 3.0625" bore.
6) Had the two fan belt system (beginning with 1942 models) to drive the accessories. One belt operated the water pumps and generator. The other belt operated the cooling fan assembly.

General Information
The integral cast-in bell housing continued all the way through 1948 (except for the Ford trucks, which received in 1948 the newer '49-53 style engine with separate bell housing). All engines during this period had front, block-mounted water pumps (with wide belt pulleys), and twenty-four stud heads with center-located water hose outlets.  Original cylinder heads for 1938 to 1942 were generally marked with "81A" for Ford or Mercury engines thru 1941; "81T" for truck engines from 1938 to 1942; "41T" heads were sold for 85/90hp trucks built from 1938 to 1942; "99T" for 100hp Ford Truck and Mercury in 1939 to 1941; and "29A" for Mercury in 1942. Heads marked "59-A" or "59AB" were used on all 90/100 hp (Ford & Mercury) engines from 1946 through 1948. The 59AB heads were sometimes used on earlier blocks in replacement rebuilds. You can find the Ford part numbers (basic 6049 and 6050 number with prefixes and suffixes) in the face of the heads and sometimes on the side edge of the head next to the intake manifold.

Additional information
The postwar cylinder blocks were also marked "59" (or "59A" or "59L" or "59X" or "59Y" or "59Z") with raised letters cast into the top of the bell housing part of the block. The Canadian version had a "C59" cast into the same area. Another block assembly (the "41A" style) was used to replace the "81A" style cylinder blocks, which were all the 85/90hp engines with 3.0625" bore. The 1938 to 1940 blocks had four small "freeze plugs" (2 each side) in the oil pan mounting surface. The 1941 (except for a short carryover) and later blocks did not have the freeze plugs. These can be noted from outside an assembled engine by the slight "bumps" in the side of the block casting, right at the oil pan mounting surface. In mid 1938 Ford modified the engine for larger diameter main bearings. For complete crankshaft bearing specs CLICK HERE. The original engines from mid 1941 to final 1942 production (when WWII ended auto production) had a raised intake manifold deck surface. Prior to these engines, the entire manifold deck surface was machined flat, right out to the edge of the cylinder deck. The postwar engines seem to have returned to the practice of machining the intake deck all flat again. The foundry would also place what were probably "lot" or "production" numbers in the castings on all blocks. These were usually a small group of letters and numbers cast on the top of the bell housing....right next to the vertical surface of the back of the block. Unfortunately, any records of these numbers are long gone and they provide no clues as to the particulars of any engines. 

Water jacket holes in the top of the cylinder area of the block will tell you what years the block may be:

1938 Blocks: Large triangular shaped holes between the center cylinder bores

1939-42 Blocks: Three openings between the center cylinder bores: top one is triangular;
center and bottom holes are trapazoidal (or keystone) shaped.

1945-48 Blocks: The three center openings: top one is triangular;
center and bottom holes are large round holes.

Flathead_BlockID-1941-42.jpg (50297 bytes)    Flathead_BlockID-1946-48.jpg (81523 bytes)    

All 24 stud engines using cast iron heads were equipped with dome-top pistons (in either aluminum or steel).  Engines built through 1939 had a pressed-on timing gear on the camshaft. Beginning in 1940 this gear was bolted on to the camshaft. All engines up through 1948 had "mushroom" style valve stem ends and split valve guides. Some engines (including 59A style) had removable hardened valve seat inserts. It's not uncommon for an early (pre 1946) engine to have the valve seats installed by an engine rebuilder at some point in its life.

As for original paint colors, the Ford and Mercury engines through 1940 were a dark green. Ford cars continued the color until 1942. Mercury engine had a dark blue color from 1941 thru 1948. Postwar Ford engines were dark blue thru 1948. Ford truck engines were generally the same as Ford cars during the years of this group.

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