PLUMMEN wrote:remember the best running motors are the ones where you can just see the witness marks where pistons and head were just touching! :laugh:
Valve pocket width is overlooked by most people. Piston companies generally, make one size to fit all,even motors with oversize valve dia. (who would want to stock, a million diff pistons, for the average guy)
Valve pocket dept, can kill engines! To wide of width can be a loss of some real power. For racing it is worth the extra money to have the valve pockets custom fitted to your needs.
Extra width also reduces compression. Pro stock cars run the side clearance at about .050" with no problems at 10,000 rpms.
Next time you build an engine, try this. Take an old valve and cut the head off of it, sharpen the stem to a point. Set your head (with no valves on the motor) Then use your "valve stem punch" to mark where the center of the valve would hit the center of the valve pocket. Now that you have a mark in the center of the valve pocket, set your ver.calipers to the valve head radius. Use your valve pocket "center mark" to lay out a circle in the valve pocket. Now look at how much valve to piston side clearance you really have?
The same tool with a few mods, can be used to check the relationship of the valve angle, to the angle of the valve pocket.
Just something to check out, next time your bored. I have an interest in this, because I am using pistons without real valve pockets.
