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Difference Between 8BA and 59AB Fatheads

Difference Between 8BA and 59AB Fatheads

Story and Photos by Zac Parks

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When shopping for the right Flathead for your traditional Hotrod, knowledge is power. You need to know the differences and which one is right for your build. The two most common Flathead motors are the 59AB (1946-1948) and the 8BA (1949-1953). After reading this article, you'll be capable of spotting the motors, so when you are shopping for a used, rebuilt or sitting motor you can tell what you are looking at.

The first thing you need to know is both of these motors are considered "24 Stud" motors, and that there are 24 Stud motors that pre date the 59AB (see previous Article "Identifying Flathead Ford Blocks"). So let's dive into both of their characteristics. 

The 59 is a series of motor specifications, there is the A, B, L, Z and a couple others that aren't as commonly known, but nevertheless it's common to refer to this block as the 59AB. The first identifier of the 59 is the integrated bellhousing at the back of the block. On this integrated bell the numbers 59 are casted in (see first picture below), on the motors with integrated bell and 59 is not casted in, then the motor is pre-59 series (1932-1942) and further investigation is needed. Another characteristic of the 59 series motor is the coolant outlet is in the center of the heads seen in the second picture below.

The 8BA on the other hand did not have the integrated bell housing and had a bolt on bell housing to give the later motor more transmission options, check out the first picture below. Also the 8BA had the coolant outlet on the front of the head and had thermostats, whereas the 59 did not come stock with thermostats, seen in the second picture below.  

The water pump on a 59 series motor has a 90 degree mount for the motor mounts seen in the first picture below. Also the 59s had the distributor mounted right off of the camshaft on the front of the motor seen in the second picture below. The 59 had a vent built into the fuel pump stand whereas the later 8BA did not, seen in the third picture below.

Here you can see the 8BA water pumps with its motor mounts being below the pump seen in the first picture below, note that the 8RT was a truck motor and had similar motor mounts as the 59. The 8BA had its vent aka Road Draft Tube, located at the front of the intake, making these intakes non interchangeable without modifications, check out the second picture below. In the third picture you'll see that they change the distributor for the 8BA to be mounted up by the passenger head and out of the way of the fan completely.

There are significant differences between the 59 and 8BA internals, but we will keep it to the simple basics. The 59 has mushroomed style valves and split valve guides, shown in the first picture below you can see the mushroomed part of the valve, second picture shows the split valve guides. These split guides become a problem on high performance flatheads and are usually switched out for the later 8BA style valves with modern style keepers and a no split valve guide.

Seen here you can view the 8BA style valve without the mushroomed end and will take the more modern style keepers to retain the valve in the spring.

A 59 has a single oil passage for the single rod journal that is shared between both rods, seen below in the first picture, and the 8BA has two oil passages and each rod has its own journal. Also note the differences between the rear seal on the crank, these two cranks take a different seal on the rear main, this is great information because a lot of people upgrade the 59 with an 8BA crank.

Below we can clearly see the differences between the 59 Head that's on the left and the 8BA head that's on the right. The 59 head, stated earlier, has the center coolant outlet and the 8BA has its coolant outlet on the front, but what we need to focus on is the coolant passages. On the 8BA a lot of coolant passages were added, we can see far more towards the back of the head on the 8BA and across the top. It's common for  hotrodders to put 59 style heads on a 8BA, but note you would have to block the front most coolant passage on the block head surface and that you would be significantly decreasing your coolant flow.  

The 8BA had an upgraded oil pump over the 59. Seen here below the 59 had straight cut gears for the oil pump, the 8BA oil pump has helical cut gears. 

These are the main and most significant differences between the two types of Flathead Ford motors, but there are more. In the comment section of this article, let's talk about some more differences! Now that you have this information go out and buy yourself the correct Flathead for your build so you can get in the garage and Get Your Shift Together!

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Sean Kelly - April 16, 2023

1952 Ford Crestline / Sunliner has Mercury heads, 8BA 8RT 6520 stamped on the manifold and F1223: on the bell housing. Can you please tell me if this is ford or mercury and what year?

The car is also falling on its face when accelerating. Do you know of any mechanics near Jacksonville, FL? Man what I wouldn’t give to have you pimp this ride. Thx for all your info, Peace, Sean Kelly

Hi - April 7, 2023

That’s very informative. Thank you It now makes it easy to remember what’s what.

pete graham - March 13, 2023

Hi, I have a 59A engine that has the hand crank provision on the crank snout. Is something amiss here? I know the engine has been apart as it has adjustable lifters. Engine color was blue and has a green pan on it. Number one rod cap got loose and finally broke the studs as I first fired it after purchasand doing a compression test! Am in the process of further investigation this morning. Thank in advance Pete

RICHARD Houle - January 23, 2023

great info thanks

Henry - March 15, 2022

As you probably know and a lot of people do not, 5 means 1945, when they were first produced and 9 means 239 cu. in. , the previous engines were 21 A, 2 for 1942 and 1 for 221, 91 A was 9 for 1939 and 1 for 221 cu. in., 81 A was 8 for 1938 and 1 for 221 before that it was the prefix of the model of the car 18 for 1932, 40 for 1933/34 and so on until late 1937 when they went to 24 stud

Zac Parks - March 15, 2022

Thanks Bernie!

Bernie - March 15, 2022

Thanks for this information .

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