Quote:
Originally Posted by chuck stevens
Thanks everyone, I was afraid this would open a can of worms. Walt has an idea, use 3 3/4 pistons and trim the domed area of the heads to get some clearance. This wouldn't effect the compression, and might help flow. Now I'm wondering how much material is in the head. This would work as long as the top ring is not too close to the top of the piston hummmm.
I'm trying to use up some of my old flathead stuff, thanks again, Chuck S.
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You're only talking the removal of less than 1/16 of material - so unless your heads have been reworked before, don't see an issue. The added benefit is that you could "tune" the squish area over the piston to get exactly what you need for best performance (which is about .040).
Most piston/gasket/head combinations (out of the box) have a lot more squish than is needed. I have a 3D CAD model that I made to tune my dome height (using a CNC machine center and a 1/4" ball mill to machine the contour).
Flathead3DModel.jpg
Once I have the crank and a rod and piston in the block (to accurately measure from), then I add my compressed head-gasket thickness (usually about .050) and I can then determine how much clearance I need above the piston. I use these numbers in my 3D CAD model to setup the dome location and have the domes cut to exactly match what I need.
Also, you can use 'clay' in the head domes to figure out the dome shape - in many cases the head doesn't match the pistons anyway.