Ford Flathead engine identification - Part II

Posted by on Nov 16 2015 in HowTo, FAQ and Tech Hints, Ford Trucks pre '48, Ford Cars pre '48

Part II of the Ford Flathead identification article. After we handled all 21 stud engines, the 60 HP and the monster 337cui engines, we'll look closer to all 24 stud engines in this part. The american Ford V8 24 stud Flatheads where build from 1938 to 1953. The displacement is 221, 239 or 255 cubic inch. The biggest problem in identifying: all engines look very similar.

The second problem is that even the Ford literature did not care about the year an engine was build, just which engine will fit in which car or truck. The last problem: World War 2. Ford produced flathead parts for military use and had no civil production from 1943 to 1945.

Let's try to divide our table from Part I:

studs	cui	HP	build from	build to	bore	stroke
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

Different Distributors

Ford Flathead engine identification - Part II — 21 stud with Divers Helmet or Eggshell Distributor

The earlier models have, like all 21 stud engines, a so called Divers Helmet distributor (sometimes called Eggshell distributor). This distributor applies to all engines from 1932 to 1941, so for the 24 stud engines we are looking at, all 1938 to 1941.

The 1942 to 1945 engines had the Crab-Style distributor (see picture below).

The 1946 to 1948 engines had the round style distributor. All three distributor styles are located on the middle of the front side of the engine.

All 1949-up engines have a modern style distributor located on the top front of the engine.

Water outlets

The water outlet design on the cylinder heads was changed in 1949. 1938 to 1948 cylinders had the water outlet in the middle of the head (see right picture below). In 1949 the outlet moved to the front of the engine (left picture). This design was keept till the end of the US flathead production line in 1953.

The Pencil Test

All pre WW2 flathead engines, including the 21 stud, will pass the so called "Pencil Test". This pre war blocks have a tiny shelf above the timing cover. The shelf is deep enough to horizontal lay a pencil on it. All post war blocks will fail the pencil test.

studs	cui	HP	build from	build to	bore	stroke	construction details	model
24	221	85	1938	1940	3.0625	3.7500	Divers Helmet distributor, water outlet on center of cylinder head, passes pencil test	81A/91A/01A
24	221	90	1941	1941	3.0625	3.7500	Divers Helmet distributor, water outlet on center of cylinder head, passes pencil test	11A
24	221	90	1942	1942	3.0625	3.7500	Crab-Style distributor, water outlet on center of cylinder head, passes pencil test	21A
24	239	95	1939	1940	3.1875	3.7500	Divers Helmet distributor, water outlet on center of cylinder head, passes pencil test	99A/09A
24	239	100	1941	1941	3.1875	3.7500	Divers Helmet distributor, water outlet on center of cylinder head, passes pencil test	19A
24	239	100	1942	1945	3.1875	3.7500	Crab-Style distributor, water outlet on center of cylinder head, passes pencil test	29A
24	239	100	1946	1948	3.1875	3.7500	round distributor, water outlet on center of cylinder head, fails pencil test	69A/79A/89A/ 59A (Mercury all years)
24	239	100/110	1949	1953	3.1875	3.7500	modern style distributor, water outlet in front of cylinder head, fails pencil test	98BA ('49) / 8BA ('50-'53)
24	255	110/125	1949	1953	3.1875	4.0000	modern style distributor, water outlet in front of cylinder head, fails pencil test	CM (all years)

It's important to know that the cylinderhead marks can be differend from the engine model. For example 81A cylinderheads were used from 1938 to 1942. The same periode trucks used 41T cylinder heads. 99T heads were used on trucks in the years 1939 to 1941.

Part III will follow...

This entry was posted by Zapp and filed under HowTo, FAQ and Tech Hints, Ford Trucks pre '48, Ford Cars pre '48.

21 comments

Comment from: John Tary Visitor

I have a 1935 Ford pickup.The truck has a later 24 stud engine with crab style distributor.The heads are marked with the letter A.Can anyone I.D. them for me.Thank you John.

Comment from: zapp Member

Just an “A” on the heads or two letter followed by A? Any number on the top of the bell housing? Some pictures may help.

Comment from: dennis Visitor

I have just bought a 1948 flat bed truck flat head motor. The heads have number c-7RAA on them and I can not find info on this number, Can any one help me?

Comment from: Tom Visitor

The flat head Ford and Mercury engines were in Ford, Mercury and (Meteor and Monarch Canada only models) in the 1954 model years. The Y-block engine did not arrive until 1955.
The long stroke Mercury engines were in the Customline and Crestline models of 1954 Fords in Canada.

Comment from: Johnny Pool Visitor

Hi ,I have a 24 bolt flathead with numbers

1B45176*
Could you ID for me please ,ie year and HP

Regards johnny

Comment from: Brian Falkner Visitor

Dennis, C7RA heads are Canadian original equip on their 48 F1’s & are & 6.7-1 or 6.8-1 ratio from memory. They made them in aluminium & cast iron with alloy being slightly higher comp.
Brian D F. New Zealand

Comment from: LOUIS E SIVLEY Visitor

WHAT MAKE OF MERCURY EAC HEADS MOTOR NO 2AYC ALSO YEAR

Comment from: hector Member

1953 monarch flat head # on head 8rt6049d & another # 310d can you id this engine for me any help would be appriaced

Comment from: Alisa Dove Visitor

Need help identifying a flathead motor. All I can see is what looks like the stamp 68-6049B. Any help would be appreciated.

Comment from: Bruce wilson Visitor

Trying to identify a couple of flatheads I have. All 3 have no heads ,no distributor, but a set up to take a 3 bolt distributor,,,,,,looking to see what year they are? Also they have ,,,59 ,,,,stamped on the bell housing top

Comment from: Parrish Galliher Visitor

My 24 stud V8 only has the number “20” on top of the cast bell housing, no letters. Does anyone know what year it was built?

Comment from: Parrish Galliher Visitor

My 24 stud V8 only has the number “20” on top of the cast bell housing, no letters. Does anyone know what year it was built and what the HP is?

Comment from: William Visitor

In the first comment “John” said letter “A”
Have been looking for info on the same engine myself.
Engine has a “Crab Claw” distributor, Dark Green color.

Comment from: mario Visitor

can anyone help identify this v8 flat head engine. L11733 and under this number 59

Comment from: Mark Karol-Chik Visitor

John Tary-
The heads with the A on them are 1942 Mercury.

Comment from: Jukka Virta Visitor

Hello, I have a 24 stud flathead and there is - F23 3 - X5 on the integral bellhousing upper edge. Raised intake flange. Heads are with casting numbers either CAE or GAE - RH and LH. with the Ford USA below. Center water outlets. Crab style front distributor and truck water pumps. What year, size or use it is from?

Comment from: Bill Hardy Visitor

I have a 24 stud flathead I’m trying to identify. On the right top of the bell housing are g2123. The heads are cast EA B J 32 and H 72.

Comment from: whoody Member

Hi all, i have a 21 stud engine with no numbers on the rear bellhousing, i no its between 32-36. Only have the engine number * C18ZF5589 * any help would be great, thanks Steve

Comment from: gary3_aero Member

I’m looking at purchasing a Flathead, but a bit confused because the different components don’t seem to match up… 59L on the block, 41T on the covers - so these two together seem to indicate it originally came from a truck. But the kicker is the distributor is a Diver Helmet style - which doesn’t seem to match the newer block and covers. Is it possible to actually make that distributor work for rest of the setup?