Thread: Greetings from the UK

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FreewheelX1/Len, I don't have a machine shop and I am pathetic with a hand grinder but for what it is worth here are two pages from one of my alltime favorite hot rod books: "Speed and Power Handbook", 14th Edition, Newhouse Automotive Industries, copyright 1952. Most of the old folks on this forum know this so excuse me if I state the obvious. Most all the flathead engines have the main combustion chamber volume over the valves along with the spark plug hole and then a narrow squish area over the top of the piston. Thus if/when you shave the head you actually narrow the slot between the valves and the cylinder and end up reducing flow. The solution is to grind away the lip of the cylinder wall near the valves. However, the lost art is the hand grinding of the "relief" in the top of the block. On a long and heavy 8 cyl block you would need to find a very large bed on a milling machine. I suppose you could do a light cut on the top of the block to "deck" it to what ever you want relative to the pistons you have, but maybe something like a resurface cut of 0.005" would make sure you start out with a flat surface. Then you need to tilt the block only about 1 to 2 degrees moving the valve side down slightly. Then set up a milling routine to follow the outline of a head gasket to mill out the top of the block. Also you don't want the edge of the relieved block lip below the top ring of the pistons at TDC. Thus with a modern programmable milling machine the process could be made precise and equal on all cylinders, but that process sounds expensive to me. The alternative of tracing out the head gasket and using a hand grinder for the reliefs would require a lot of skill to make them all nearly equal and I don't see any way to cc the block the way you can with a head pocket. Anyway here are two pages on how to do it!

Note added in edit mode: It may not be necessary to slavishly follow the head gasket outline behind the valves since there is probably plenty of open space above the valves, so to make it simpler a rectangular shute the width of the narrow part of the head gasket should be sufficient to help flow back and forth over the edge of the cylinder on the valve side. You also want to avoid cutting away the edge of the valve seats so the shute could start right after the valve seat and extend toward the cylinder going from nothing at the valve seat to 1/8" depth at the cylinder lip. Good Luck!
Don Shillady
Retired Scientist/teen rodder