1932 - Model 18 - 65 HP @ 3400 Introduced in 1932, the first Flathead used a gear-driven camshaft with a fabric cam gear. Solid valve tappets. The 221 CID engine had a bore and stroke of 3-1/6" x 3-3/4". The compression ratio was 5.5:1. Hey, they had some quality gasoline in 1932, huh! Cylinder heads were clamped to the block by 21 studs. The water pumps were mounted on the heads. 18mm spark plugs were used. Intake and exhaust valves were both 1.54" diameter, with 5/16" valve stems, running in tungsten chromium steel guides. The seats were integral with the block, no inserts were used. The connecting rods measured 7", center to center, with full-floating bearing shells. The crank pin was 2" in diameter. The forged steel crankshaft ran in only three, 2" main bearings of poured babbitt. The carburetor was a Detroit Lubricator single-barrel. The bellhousing is cast integral with the block.
1933 - Model 40 - 75 @ 3800 Change to aluminum cylinder heads with compression raised to 6.3:1
1934 - Model 40A - 85 @ 3800 Carburetion changed to the Stromberg 48 two barrel with 1.03" venturis. Good for an extra 10 HP.
1935 - Model 48 - 85 @ 3800 No significant changes.
1936 - Model 68 - 85 @ 3800 Changed from aluminum to steel pistons.
1937 - Model 78 - 85 @ 3800 Major face lift. The cylinder heads were redesigned, moving the water outlets to the center of the head and the water pumps moved to the block. This helped solve problems with overheating. Head-mounted pumps tended to cavitate in the steam rather than pump cool water. Pistons gained domes while the combustion chamber shape was revised to accommodate them. This added squish and reduced knock. Compression also dropped to 6.1:1. The carburetor was changed to the Stromberg 97. The cast iron crankshaft's main bearings were enlarged to 2.4" and the babbitt was replaced with modern inserts.
1938 - Model 81A - 85 @ 3800 Spark plugs changed to 14mm thread.
1939 - Model 91A - Ford 85 @ 3800, Mercury 95 @ 3600 The Flathead revised for the new Mercury car line. Ford kept 3-1/16" bore, the Merc got a 3-3/16" bore and resulting displacement of 239 cubic inches. The cylinder heads bolt pattern was changed to the modern 24-bolt design to improve sealing. The same heads were used on both engines, giving the Mercury a slightly higher 6.3:1 compression ratio. The crank main bearing diameter was again increased, now to 2.5".
1940 - Model 01A - Ford 85 @ 3800, Mercury 95 @ 3600 No significant changes.
1941 - Model 11A - Ford 85 @ 3800, Mercury 95 @ 3600 No significant changes.
1942 - Model 12A - Ford 90 @ 3800, Mercury 100 @ 3800 New heads raise compression to 6.2:1 for the Ford and 6.4:1 for the Mercury.
1943/45 No civilian automobile production due to World War II.
1946/48 - Model 59A - 100 @ 3800 Ford and Mercury now use the same engine. Both use 239 CID. Compression ratio raised to 6.8:1.
1949/53 - Model BA - Ford 100 @ 3800, Mercury 112 @ 3800 Bellhousing changed to modern removable unit. Cylinder heads altered yet again, moving the water outlets to the front of the engine. Heads are now attached with bolts rather than studs and nuts of the earlier engines. Crankshaft counterweights were modified and rod bearings are now normal style non-floating inserts. Mercury is stroked to 4", resulting in 255 CID. Ford engines now use a cast iron crank of 3-3/4" stroke. Mercury rod bearings are 2.14" which allows for offset grinding to the stock Ford size of 2", for a free 1/8" stroker. Distributor is changed to single points with an 8-lobed cam, using vacuum advance only.
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