Flathead Cylinder Heads

[carryinwood]

Im new to the Flathead Arena, just wondering whats the difference in the Factory V-8 Cylinder Head to the After Market ones..Besides the Aluminum and Cast Iron Material. Can the Factory ones be Hopped Up in some way? Thanks in Advance for any Help/Ideas.

 

[richard crow]

you new to the flat head engine if you want a nice smooth running eng leave it stock enjoy it the way it was desigened

 

[Ol' Ron]

The combustion chamber is different in all these heads to achieve the results you are looking for. In most cases it's just to raise the compression ratio. Most stock flathead engines have aprox 6:1 CR. Raising it to 8;1 will improve the torque output of the engine as well as the fuel economy. Yoy can also select a different head to improve performance, such as installing an EAB head on an earlier engine. MIlling theheads a small amt can also improve combustion, but you have to be carful here as you can bend valver a break oistons if your not measuring what your doing. Get a copy of JWL's book ot mine, might help.

 

[51woodie]

I'm not that familiar with "hopping up" a flathead, but I don't think just changing the cylinder heads on a stock engine will help all that much, other than what Ol' Ron says. Another few horsepower is not going to motivate, in my case, a stock 3500 pound '46 Coupe, a whole bunch more. I break into a sweat when a VW Bug pulls up be side me at a light, and the driver revs the engine!

 

[tubman]

I like to run Edmunds finned aluminum heads. They are not currently made, but a lot were made back in the '50's and '60's, so some are available if you look hard enough. I like them because they have the spark plug re-located juuust enough to allow the use of extended tip plugs. (Stock heads and most aftermarket units have the plug relocated over the exhaust valve, which will quickly close the gap on these plugs). In my opinion, getting the spark out there in the combustion chamber is a big advantage. In any case, if you decide to run any kind of aftermarket heads, make sure you get the correct reach spark plugs. Most aluminum heads take a longer than stock plug, and running stock plugs (Champion H-10's or equivalent) will shroud them badly.

As "Ol' Ron" says, aftermarket heads will increase the compression ratio, which is always good (even the cheapest fuel available today is better that what was around when these engines were designed). He also touched on better fuel economy and power, both of which are improved by optimizing the "quench" in the combustion chamber. This means trying to get the clearance between the top of the piston and the head to around a uniform .045-.050" when the piston is at the top of the stroke. On every set of heads I install, I check for the existing clearance and work on them until I achieve this measurement. I believe it is time well spent and makes you feel like a real "Hot-Rodder".

I will take issue with the previous poster in whether this is worth the effort. On the first flathead I had built (a 276" Mercury), I just bolted on a set of spankin' new Offenhauser heads and let it go at that. The car ran and performed fine, but it never had the "ooomph" I thought is should have had. On my last two engines, I have used worked over Edmunds heads with a little increase in carburation, a mild cam, and a good ignition. I am much happier with the performance of these engines than the first one which was built for a higher level of power.

As to cast iron or snazzy finned aluminum heads? That's a matter of personal taste, but if I build another engine, you can bet I'll spend a bunch of time on the heads to get them to where I want them.