The Flathead 101

Posted by Ryan on October 18, 2006 and filed under: Feature Articles, Tech

The Flathead Ford

My history with the flathead is relatively short. Sure, I admired them like any other self respecting traditionalist, but my actual working knowledge was limited to some degree. It wasn’t until Tardel and I began concepting my a-coupe that I really started to get enamored in the details. In doing so, I kept notes on the basics and while most of this info is elementary to a lot of you guys I do think some might find it valuable… This stuff is coming straight from my ten year old notebook full of pencil scratches and grease induced finger prints. Take that as a precaution of sorts. This stuff has not been edited at all!

1932
The first of the flatheads made legendary by the body that surrounded it.

CID: 221
Bore: 3.0625
Stroke: 3.750
Comp: 5.5:1
HP: 65@3400rpm

1933
Henry bumped compression and made some minor ignition improvements in ’33. Power increased by 10hp.

CID: 221
Bore: 3.0625
Stroke: 3.750
Comp: 6.33:1
HP: 75@3800rpm

1934
This is the first year that the flathead really got rave reviews from the common man. Improvements listed include the new Stromberg model 40, new intake, and a “chastely” steel crankshaft. Ten more ponies…

CID: 221
Bore: 3.0625
Stroke: 3.750
Comp: 6.33:1
HP: 85@3800rpm

1935
The first year of the Stromberg Model 48.

CID: 221
Bore: 3.0625
Stroke: 3.750
Comp: 6.33:1
HP: 85@3800rpm

1936
The first year for the Stromberg 97. I believe this is also the first year for insert main bearings instead of poured…

CID: 221
Bore: 3.0625
Stroke: 3.750
Comp: 6.33:1
HP: 85@3800rpm

1937
The ultra cool and very small v860 enters the mix, but I’ll stay focused on the big motors which gets larger water pumps, insert bearings, and new pistons. Horsepower jumps again.

CID: 221
Bore: 3.0625
Stroke: 3.750
Comp: 7.5:1
HP: 94@3800rpm

1938
The Stromberg 97 is scrapped for the Holley. Oddly, factory horsepower goes down as listed. More research please…

CID: 221
Bore: 3.0625
Stroke: 3.750
Comp: 6.12:1
HP: 85@3800rpm

1939
The 21-stud flathead heads are replaced by the 24-stud heads. Mercury introduces the 239.4 cubed motor with lots of HD changes.

Ford
CID: 221
Bore: 3.0625
Stroke: 3.750
Comp: 6.12:1
HP: 85@3800rpm

Merc
CID: 239.4
Bore: 3.1875
Stroke: 3.750
Comp: 6.3:1
HP: 95@3800rpm

1940
The last year for the v8-60… No major changes for the big motors.

Ford
CID: 221
Bore: 3.0625
Stroke: 3.750
Comp: 6.12:1
HP: 85@3800rpm

Merc
CID: 239.4
Bore: 3.1875
Stroke: 3.750
Comp: 6.3:1
HP: 95@3800rpm

1941
Getting ready for war… No major changes

Ford
CID: 221
Bore: 3.0625
Stroke: 3.750
Comp: 6.12:1
HP: 85@3800rpm

Merc
CID: 239.4
Bore: 3.1875
Stroke: 3.750
Comp: 6.3:1
HP: 95@3800rpm

1942
Power rating increases for both Ford and Merc as listed but no mechanical differences. More research needed… Ignition coil is no longer bolted to the distributor. This is the first year for the crab style dizzy with separate coil. Edelbrock was getting started with their dual intakes and heads around this time.

Ford
CID: 221
Bore: 3.0625
Stroke: 3.750
Comp: 6.12:1
HP: 90@3800rpm

Merc
CID: 239.4
Bore: 3.1875
Stroke: 3.750
Comp: 6.3:1
HP: 100@3800rpm

1942-45
Too busy killing Nazis to make flatheads.

1946
Ford finally gets to run the big Merc motor. Improvements include pressurized cooling, aluminum pistons, and new bearings. The angle between the valves is decreased from 101.5 degrees to 100 degrees to reduce cracking. The fan is moved up to above the dizzy. First year for the one piece crab dizzy cap.

Ford
CID: 239.4
Bore: 3.1875
Stroke: 3.750
Comp: 6.3:1
HP: 100@3800rpm

Merc
CID: 239.4
Bore: 3.1875
Stroke: 3.750
Comp: 6.3:1
HP: 100@3800rpm

1947
Nothing new really…

Ford
CID: 239.4
Bore: 3.1875
Stroke: 3.750
Comp: 6.3:1
HP: 100@3800rpm

Merc
CID: 239.4
Bore: 3.1875
Stroke: 3.750
Comp: 6.3:1
HP: 100@3800rpm

1948
The F7/F8 trucks get a huge 335.7 inch motor, but they aren’t available for the cars yet.

Ford
CID: 239.4
Bore: 3.1875
Stroke: 3.750
Comp: 6.3:1
HP: 100@3800rpm