1939 heads on 59AB engines

You can but the valve pockets will need to be opened up a tad to clear the valves. Not the depth but around the edge. KR Wilson made a fixture with a cutter for this.
 
Here’s a photo of it
 

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Depending on what cam you're using, you may need to do more than just the eyebrow radius at the top of the chambers. Once you get the upper radius areas done, then check to make sure you have clearance above the valves (up at the top of the chamber). The valves are canted in a manner that causes most clearance problems to be at the top of the valve (where they are the highest above the deck surface).
 
What is the purpose of using early heads for a lower horse power engine on a higher horse power (239 CID) engine.? It would appear to me that this would be a step backwards.
 
blucar said:
What is the purpose of using early heads for a lower horse power engine on a higher horse power (239 CID) engine.? It would appear to me that this would be a step backwards.
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The smaller chambers give you a higher compression ratio. A lot of guys also use to "fill" the transfer area "dip" with weld to increase the compression ratio even more. This is especially true if the block was relieved - as the relief already increased the flow (but lowered compression), so gaining some compression back by filling the dip area on stock heads would offset the CR loss.

One of the most important things is to also tune the "squish" (piston to head clearance) to .040 to .045. Having a tight squish is super important for overall performance (on any flathead engine).
 
The post war 59A heads have smaller chambers than the prewar 81A heads. The last center water outlet heads, the 59A-B, have slightly smaller chambers still. Sticking to post war heads is higher compression options.


The head chamber sizes are very well listed in the pdf available in the first post of this thread: https://www.fordbarn.com/forum/showthread.php?t=4336
 
Thanks to Bored Stroked for the detailed explanation:
The 59AB engine in my '36 was rebuilt in 1960 by a local machinist that specialized in engines for stock car racers in lieu of drag racing. The original rebuild was done in '54 by a shop in SLC that specialized in drag racing.. It had Offy 10.1 heads and therefore would not run on anything but premium..Not at all a good combination for everyday driving.
The second rebuild involved a larger bore, new pistons and modified 59AB heads. As I recall the machinist told me he 'milled, domed and flycut' the heads. The engine has always ran very well.
 
Those are very shiny heads!
I would check and see if the valve area already has been clearanced for use on a post war block. If not find someone in your area with the KR Wilson tool made to do that. It would help if you included your general location in your signature. For example I have a valve clearance tool, live in the Houston area, and visit the San Antonio and Austin areas on occasion.
 
Now that all that polishing is done, you should "spot face" the tops of the stud holes in the heads - to give you a nice, even, flat surface for the hardened washers to ride against.
 
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