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Discussion Topic:
Flatheads and compression/power
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Stroker |
03-21-2012 @ 7:55 AM
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Senior
Posts: 1460
Joined: Oct 2009
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I might also add that in addition to the possibility of valve interference, there is also a "choking" effect in having the area of the head between the valve pockets and the edge of the cylinder too close to the deck. It is this area that is often opened up by "relieving" the block (either by Ford or by engine builders). High compression aftermarket heads were cast with a generous "arch" in this critical area. So...to say there is "no limit" to how much you can mill a stock head when using flat top pistons may be an oversimplification.
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supereal |
03-20-2012 @ 8:50 PM
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Senior
Posts: 6819
Joined: Oct 2009
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When milling heads for more compression, be sure to "clay" the heads to be sure adequate clearance is maintained. This process involves placing modeling clay in the combustion chamber, putting on the head gaskets, and bolting the heads in several places. Turn the engine over several turns, Then, remove the heads and examine the valve area to determine if the valve heads are not striking. There was a head change at one time that required milling the valve area for clearance, so don't omit this process.
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1883warren |
03-20-2012 @ 6:16 PM
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Member
Posts: 25
Joined: Dec 2009
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The '36 engine I bought last year turned out to be insert mains and flat-top pistons. I always like a little more power and pep with my cars, but always looking absolute original if at all possible. With dome pistons, you can mill off about 1/32 inch, which gives more pep, and usually better mileage in the process, being more efficient. In my case, with flat pistons, there was no limit to what could be milled off the heads, so I went for .068 and this gave me about 9 to 1 compression. In fact, it made a real screamer out of this thing and more power than I bargained for. The mileage picked up also and this was a big plus. The rear axle is 3.68 but should be at least a 3.54 with this kind of engine power. Overdrive would be great too, but .... Meantime, my tudor is a nightmare for most at a stoplight. Cheers, Warren
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