Technical 81 A flathead

I have been cleaning the shop and moving things around. Had an engine in the back for 15 yrs. I thought it was a 59ab, but on cleaning the dust off I see it is a 81 A. Took this out of my '34 5W. Not to familiar with this one. What year would it be and what is the difference between it and the 59ab. Thanks Terry

 

The 8 in the 81A means 1938. It was designed in 1938 and is probably from that production year. Some parts carried that number into the next year's, but 39 got upgrades so it might not have been made in 39.

Lots of little things are different, but the main thing different from a 59A is the bore size and the valve angle.

 

Thanks for the info. Is it worth building or sell to a restorer ?

 

Also ask on Fordbarn.

 

Every flathead is worth building. Just depends on if you want a cruiser or a racer.

 

You need a lot more info! The 81a designation is for the cylinder head. Versions of that head were used on 221's for several years, I think through 1941, and they will fit on numerous OTHER flatheads either without change or with very simple mods...really, ALL the flatheads later than 1938. Multiple photos of block and removal of a head are really necessary to figgeritout. It can potentially be identified within a year or two with enough clues.

 

I guess I assumed the parts were all living on their original block.

 

81A was cast into some of the bellhousings. 38 was a strange year as they went from 21 stud to 24 stud. Also some of the blocks retained the 36 crankshaft with 2.339 main bearings but had 24 studs. All were 3 1/16" bore.

 

Almost all '38 24 studs apparently got the small crank 24 stud block, changeover to big crank block was apparently done late in '38 year so block of that type still got 81 A designation. The parts book labeled crank and block 81A-A
(second A at end of part number) while the 221 parts used thereafter for several years had -B at end of the changed part number. I think! Very confusing.
By visuals...the earliest 24 stud 221 has crank that ends flush with the front of the front cover like all previous flatheads. Later type (and all the later flatheads) had about 1" of crank protruding out of front cover and also the extra crank length sticking past the general plane of the pulley.
This lengthening was done to support the crank mounted fan introduced with '39 standard cars. This longer crank also had the bigger mains, same diameter used on flatheads until 1953.
Simple, yes??
The '38 24stud engines are as scarce as they are confusing.
Any prewar 24 stud engines need a lot of decoding to fully identify!

 

I've got one of those 38 81-A blocks and was going to fit a later crank. Found out that would not work. Very confusing since both blocks have the 81A cast in the bell.

 

I pulled the intake off of the engine when I pulled it just to look in the valley. Been sitting all these years. Can turn over by hand with the heads on. Guess I'll place it up for sale as I still have a 59ab left over.

 

You fire up that racing engine yet Terry?

 

Ron Holleran posted the recipe for putting later cranks in '36-38's. There was nothing exotic to the procedure really, but it required a sharp machinist with good measuring skills! It simply took removing metal from the crank mains and I think cutting one of the mains to a bit longer I think. I didn't pay much attention as i had no such block...