Technical Flathead info needed about stock and aftermarket heads?

Very new to Flatheads, I have acquired a 51 8BA. Looking at getting a set of stock heads. What should I be looking for when examining them? I've been looking at some heads with a ok head surface, lots of rust found in the water passages and some rust on the outside surface? Is it worth getting and having a machine shop clean and resurface them. Plus I have seen many on different sites and they are relatively cheap. In my opinion too cheap? Just want to make a good decisions before I spend money on worthless parts.

PS. Other than good looks and possible small horsepower gains why should I go aftermarket heads? To me its bang for buck and reliability, please assist me in gathering knowledge to make informed decisions.
Thanks Trevor

 

For stock heads, get the best pair of "EAB" heads you can find They are off of '52-'53 Fords, and have the highest compression of all the flathead heads. At first blush, Mercury heads may seem like a good idea because of the Mercury's higher horsepower rating, but that comes from the longer stroke on the Merc. Merc heads actually have larger chambers than Ford heads to keep the compression ratios consistant. Also avoid "8RT" heads, as the are truck units that also have larger chambers. The "8BA" heads you already have will also work, especially if they are milled properly. Go to "The Ford Barn", and you will find a wealth of information about "tightening-up" the squish area over the piston to .040 to .050" to increase both power and fuel economy.

Aftermarket aluminum heads are a matter of personal choice, adding looks as well as performance. In the end, machining the heads to get the proper "squish" and valve clearance is more important than looks or material.

 

heads differ in cc and in combustion chamber design.

google the different heads for pictures of the gasket side to see the difference in the brands.

compression differences: http://www.flatheadv8.org/flatratio.htm

for intakes refer here: http://www.hotrod.com/how-to/engine/hrdp-1301-flathead-ford-intake-manifold-smackdown/

Navarro and Sharp are pretty sweet if you can foot the bill...
prices: https://www.flatheads-forever.com/catalog.html

 

If you want to read up on what actually works on a flathead (verified by a lot of testing on a dyno), get the book Flathead Facts: http://www.vanpeltsalesstore.com/L-1006-Flathead-Facts-by-John-W-Lawson_p_511.html

 

After you have located a pair of heads put them next to each other and verify that the combustion chambers are the same shape between the two heads. If they pass this test imagine a line at the surface where the combustion chamber meets the block. If this is not the same on both heads it means that one head has been milled more than the other, if they are not to far off a machine shop can correct this.

Charlie Stephens