Month ago, I found myself in trouble identifying Ford Flathead V8 engines. While I was looking for a replacement engine, I found many offers with a description like "pulled out of a truck" or "8CM from a 1950 F1". Most times more information about the car it was pulled from, than the engine itself. "8CM from a 1950 F1" - with other words: I have no idea what I'm selling. Yes, the 8CM fits in a Ford F1, but the correct engine is the 8RT. Most times I had to identify the engines based on tiny smartphone photos.
Here we go, part one in identifiying Ford Flathead V8 engines...
Count the studs/head nuts
One simple characteristic of a Ford Flathead is the number of head nuts per cylinder. If someone is talking about a 24-stud, he means an engine with 24 head nuts (or 24 studs in the block). Ford has build several cylinderheads, but only 4 different heads in count of the head nuts: 17, 21, 24 and 27. If the count is 17, you have the smallest of all flatheads, the 60 HP and 136 cui flathead that was build from 1937 to 1940. 21 studs where build from 1932 to 1938. The early engines have 65 or 75 HP, all later engines have 85 HP and 221 cui. If your count is 27 you have a real monster. These Flatheads were build for big Ford trucks (F7, F8) or Lincolns. They have up to 154 HP and 337 cui. If you count 24...you can have anything else and we need to look closer.
studs |
cui |
HP |
build from |
build to |
|---|---|---|---|---|
17 |
136 |
60 |
1937 |
1940 |
21 |
221 |
65/75/85 |
1932 |
1938 |
24 |
221/239/255 |
85/90/95/100/110/125 |
1938 |
1953 |
27 |
337 |
154 |
1948 |
1951 |
Stroke and bore
If possible, measure the bore and stroke. The bore is the diameter of a cylinder and the stroke is the way a piston goes up and down. The different displacement of the 24 stud engines can be determined by these two values. The stroke can be 3.200, 3.750, 4.000 or 4.375 inch. The bore can be 2.6000, 3.0625, 3.1875 or 3.5000 inch, but these values can varies when the cylinder is bored for oversize pistons or cylinder sleeves. If the bore is somewhere between 3.0625 and 3.1875 inch, it must be a 221 cui Flathead. Let's expand the above table:
studs |
cui |
HP |
build from |
build to |
bore |
stroke |
|---|---|---|---|---|---|---|
17 |
136 |
60 |
1937 |
1940 |
2.6000 |
3.2000 |
21 |
221 |
65/75/85 |
1932 |
1938 |
3.0625 |
3.7500 |
24 |
221 |
85/90 |
1938 |
1942 |
3.0625 |
3.7500 |
24 |
239 |
95/100/110 |
1939 |
1953 |
3.1875 |
3.7500 |
24 |
255 |
110/125 |
1949 |
1953 |
3.1875 |
4.0000 |
27 |
337 |
154 |
1948 |
1951 |
3.5000 |
4.3750 |
Differences in construction details
Differences in construction details can be seen even if you have a smal photo. Let's take a look at the 21 stud Flatheads. The early engines from 1932 to 1936 had Waterpumps mounted to the cylinderheads with the water outlet on the pump. 1937 and 1938 models have the waterpumps mounted to the engine body.
If the intake manifold is present, look at the studs the carburetor is mounted. If there are two studs, it's a 1932 or 1933 intake manifold for a Detroit Lubricator carburetor. The manifold is made of aluminium. If there are three studs, it's for a Stromberg carburetor 1934 and up (see picture below article).
1932 models have iron heads, 1933 models have aluminium heads, giving the 10 HP more power.
studs |
cui |
HP |
build from |
build to |
bore |
stroke |
construction details |
model |
|---|---|---|---|---|---|---|---|---|
17 |
136 |
60 |
1937 |
1940 |
2.6000 |
3.2000 |
74 | |
21 |
221 |
65 |
1932 |
1932 |
3.0625 |
3.7500 |
waterpumps in heads, 2 stud carb. mount, iron heads |
18 |
21 |
221 |
75 |
1933 |
1933 |
3.0625 |
3.7500 |
waterpumps in heads, 2 stud carb. mount, alu heads |
40 |
21 |
221 |
85 |
1934 |
1936 |
3.0625 |
3.7500 |
waterpumps in heads, 3 stud carb. mount, alu heads |
40a, 48, 68 |
21 |
221 |
85 |
1937 |
1937 |
3.0625 |
3.7500 |
waterpumps in block, 3 stud carb. mount, alu or iron heads |
78 |
21 |
221 |
85 |
1938 |
1938 |
3.0625 |
3.7500 |
waterpumps in block, 3 stud carb. mount, iron heads |
81a |
24 |
221 |
85/90 |
1938 |
1942 |
3.0625 |
3.7500 |
||
24 |
239 |
95/100/110 |
1939 |
1953 |
3.1875 |
3.7500 |
||
24 |
255 |
110/125 |
1949 |
1953 |
3.1875 |
4.0000 |
||
27 |
337 |
154 |
1948 |
1951 |
3.5000 |
4.3750 |
Part II will follow...
This entry was posted by Zapp and filed under HowTo, FAQ and Tech Hints, Ford Trucks pre '48, Ford Cars pre '48. 16 comments
Comment from: jamesr Member
Comment from: zapp Member
The only way to be 100% sure if you have a 239 cui or a 255 cui is to measure the stroke: Turn the engine till one piston is at the highest position. Mark the position and turn engine until the same piston is at the lowest position. Measure the length between your mark and the piston position. If it is 3 3/4 inch it’s a Ford 239 engine and if it’s 4 inch, it’s a 255 cui Mercury.
But…if you don’t want to open your engine and it all looks “original", you have a high chance to own a Mercury 255 if the color is green and the cylinderheads are 8CM or EAC.
Comment from: Joe Visitor
Hi,
I am trying to identity the engine that I have. This is a description of the nomenclature on the bell housing of our ‘39 coupe: In the middle is a circle; inside the circle is the number “192″ in the upper half, and a “0″ in the lower half.
To the left of the circle is a “1″; to the right of the circle is the letter “S".
Can you tell me what block I have?
Thanks, Joe
PS: Note that the number “1″ in the above designations could also be a letter “I".
Comment from: zapp Member
Some photos might help. Atm I’ve no idea.
If I have to guess, the engine code that is most close to your (192) number is a 1941 Mercury truck engine. Does it fail or pass the pencil test? Examples for 1941 Mercury truck engines:
19D - 3/4 ton truck
19W - 1.5 ton C.O.E.
19Y - 1 ton truck
191W - 1.5 ton C.O.E. (101″ Wheelbase)
Comment from: Richard Visitor
reading part 1 found interesting and informative.
do you have part 2 on later flatheads?
Comment from: zapp Member
Yes, Part 2 and Part 3 (for V12 and European Flatheads).
http://www.45cui.com/45cui/tech/ford-flathead-engine-identification-part-1
http://www.45cui.com/45cui/tech/ford-flathead-engine-identification-part-2
Comment from: Tim Visitor
I have a 1937 Ford pickup. It has a flathead v8 supposedly out of a 53 Merc and I am trying to find out just what motor it is. On the right rear of the block are these numbers, F2723. The last number could be a B and not a 3 but I don’t think so. It is a 24 stud cylinder head.
Comment from: DENNIS Visitor
I HAVE A 51 F2 ..MY MOTOR HAS 24 HEAD BOLTS AND THE HEADS SAY 8 RT BUT THE COLOR LOOKS ORIGINAL AND IS GREEN …IVE HEARED THE COLOR IS WRONG BUT LOOKS ORIGINAL …WERE ANY 51 MOTORS PAINTED GREEN ???
Comment from: zapp Member
Mercury Engines in 1951 were green. Ford engines had a bronze color in that year. the 52/53 Ford were green or red.
Comment from: Ron Visitor
The number stamped on lh rear between head and intake is RC21026 followed by a star. Cannot find anywhere. Help.
Comment from: andreas Member
Hi, we are trying to identify my 21 studs Flathead. The cast number on the bell house says C18. Can you help? Thanks Andreas
Comment from: andreas Member
Hi, we are trying to identify my 21 studs Flathead. The cast number on the bell house says C18.
Can you help?
Thanks Andreas
Comment from: Tom Visitor
I was pretty sure that the BB Ford truck which I just purchased was a 1932 , but I have someone who keeps saying it is a 1933 . The information you gave on the engine was a clincher for me , since my engine has 21 bolt heads and the heads are iron , NOT aluminum ! Thanks so much . Now if I can just find a driver side door………………..
Comment from: rattrackr Member
I have been trying to I’d my 52 5 ton grain motor it is green but heads do not say anything I am use to seeing 8ba or 8 et only has Ford oval and M71 any idea what it is ?
Comment from: Larry Mass Visitor
I have a flatty here the tag says it was built 7 20 48 code c59a then in another spot it has c49a and co1ts and on the heads it is stamped 81t I am confused as to what size bore it should be is it a 239? the piston I removed from it measures 3.235 there is no marking on the piston that says it is oversize is this a standard size piston? I want to rebuild it and put it in a Canadian military pattern vehicle (CMP)
Comment from: tony bickel Visitor
ive got a 1935 ford flathead engine and i want to put 3x2 on it what intake manifold will i have to have make it work
I have a 1952 24 stud/bolt ford flathead 3 stud intake I have been trying to find out more about it. This was helpful to find out how to figure out what type it was. How do you tell a 239 from a 255.