As of this moment, I believe I have 2 sets of usable heads. According to my Google search of the casting #’s, the A heads were used from ‘38-‘42 so that’s obviously the ones I’d like to use but don’t want to lose any of what little power this engine has. I searched but couldn’t find any answer as to any performance difference between these 2 sets, found a couple neat charts but didn’t see my stuff listed. I will cc them if I have to but was hoping this was like the 429/460 stuff I’m used to and it’s in print what ya got per casting #. Thanks in advance
The valve angle was very slightly changed during wartime, so the heads are slightly different. Whatever set you use, I highly recommend you lay them on the engine with no gaskets or head nuts. Then rotate the assembly to check for clearance.
This may help with the differences in heads for compression. Both the Fordbarn and the HAMB have good articles on checking flathead clearances that alchemy told you to check.
The simple answer is to use the "A" heads with an early block. In addition to the slight difference in valve angle mentioned by @alchemy, the "59A" heads are for the larger (3 3/16") bore engine, and you may actually lose some compression. Of course, there are too many other factors in play here that make a definite answer impossible. Modifications to the engine, or the heads themselves may have been reworked over the last 85 years etc. The way to gain performance with the heads is with careful measuring, milling, and other modifications to increase compression and optimize combustion characteristics.
My bud closed his 'Early Auto' shop in San Jose, and 'gifted' me a nice 59A engine, .040" over, recent rebuild. Heads are the 'A' type, but the block has the factory relief. I have a fresh Winfield SU1A cam, (Delta) on a NOS blank, and a '53 Ford crank and rods. (std. Ford 3-3/4 stroke) Consideration: .040" overbore may compensate for compression loss from relief, but I'll end up CCing heads to know. I also have some 59AB heads, so if not satisfied, may have to go Navarro aluminum. (Match my Navarro 2X2 intake) Edit: The compression chart finally downloaded, so I am now armed with 'that knowledge'! Good database to build from... Thanks, @patterg2003 !
The "A" letter heads are for the '38 - '42 59A 221 cu. in. engine. To use the later 59AB heads, the combustion chamber needs to be enlarged to provide valve clearance. The valve spacing was a little different on the later heads. A clay check is a good idea before you use them. Also, there is a service bulletin on altering the center cooling passages to provide better cooling. Simple to do yourself. More info is also available in the Mechanics Hand Book, I believe, available from parts vendors. I have a pair of freshly milled "A" letter heads (.060) in the shed. If you could use them, post a private message.
Given his user name, I think he's working on a 1939 Ford. The "59" means first issue 1945, 239 ci. The number cast into the "A" heads is "81A", first issue 1938, 221 ci. That's how Ford determined their part number prefixes in those days.
'32-'36 have the water pumps in the heads. '37 has 21 stud heads, but they have center water outlets and water pumps in the block.
The earlier 'A' heads should give you more compression - which is a good thing. I would clay the valves (up at the tops) to see if there are any interference issues. If the valves don't touch without a head gasket in place, then you are good to do. Don't BOLT the head down solid when checking clearances - just in case a valve hits the upper part of the eyebrow area of the chamber (you don't want to bend a valve). The 59AB heads should have larger chambers than the earlier 39-42 A heads. Also, you should consider "tuning" the piston to head clearance. I always check this when building an engine - as you want .040 to .045 above the piston tops (with gasket in place). Having a tight squish area really improves flathead performance. So, you may need to mill your heads to achieve that final clearance (obviously this assumes the head-gasket is on). Important: If you mill the heads, then make sure you check/validate your valve clearance once again. Depending on the cam, you may need to use a rotary file in an air grinder to add clearance at the top (eye-brow) area of the chambers. The valves are angled to the deck, so the area they will hit is at the tops. The driver's side of the engine will have higher valve locations (about .040 higher) than the passenger side (due to differences in valve angles - based on crankshaft offset).
Just a note: The "A" letter heads that I have came off a strong running '39 engine with no valve clearance issues on a stock cam. The bad thing is I discovered that the block was cracked across the valve chamber and up into the lifter bores on both sides. You win some and you lose some, I guess.
Just a note: The "A" letter heads that I have came off a strong running '39 engine with no valve clearance issues on a stock cam. The bad thing is I discovered that the block was cracked across the valve chamber and up into the lifter bores on both sides. You win some and you lose some, I guess.
'36 was the last year for water pumps in the heads. '37 and the first few months of '38 production had 21 stud engines with the water pump in the block like all later flatheads. The 24 stud engines came out a few months into the '38 model run. Ford used up their supply of the 21 stud engines before they started installing the 24 stud engines. All engine/trans units came out of the River Rouge plant and were shipped out to assembly plants around the country. The prefix on a Ford part number tells you the first thing it was used on. 81A prefix indicates a part first used on '38 Ford cars (if a part was used on both cars and pickups, it will have a passenger car part number prefix.) 81C would indicate a part first used on '38 Commercial (pickup and panel), 81T would indicae a part first used on '38 big truck. Somebody who knows the Merc flatheads better than I do needs to say something about the 99T heads--that was for the '39 Merc engine that was also an option rated at 95 HP used in the '39 big trucks.
You missed the fact (that I had pointed out), that the second digit of the prefix was the last digit of the engine displacement. Thus "81"is 1938 model year 221 ci, while "99" is 1939 model year, 239 ci displacement. Mercury prefixes were the same as Ford, so no "extra knowledge" is needed.
Thanks for the replies! I realized while reading all of these I gave the impression that I was messing with the original engine but I am not. It's a 59AB
What many do not know or realize is that the 221 engine was used throughout the war years as replacement engines. Ford had a fairly large inventory of them and sold them until at least 1945. Even used them in some light duty military vehicles. During those years, Joe Lunchbox had to take whatever he could get and was damn lucky to get that.
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