Note: As I mentioned to him in a message, there are two distinctly different piston dome shapes that I frequently see:
1) Has three different radii, a "pointy" crown center and was used in many stock engines as well as in some cast pistons (like some of Egge's and old 4-ring Jahn's).
2) Consistent radius type - which matches the piston crown shape of many aftermarket pistons - like Ross, like the old Jahn's 3-ring. etc..
Most modern aluminum heads are designed for a consistent radius type of profile - type #2 up above. The potential challenge is that the piston crown shapes of #1 do not fit all that well on many of the aluminum heads. What happens is the "pointy" crown area at the top wants to hit the center of the dome shape in the head - as not only is the shape different, but the center sticks up a lot higher than a Ross type piston.
The other issue is that you cannot get a correct squish dimension above these pistons - as you have to use too MUCH clearance to stay above the pointy crown - leaving way too much clearance above the rest of the piston . . . and a lower compression ratio as a result. Flatheads REALLY like to have a consistent .040 to .045 squish above the piston.
Due to this issue, I don't like to run the "pointy" style of pistons (if I have a choice). If I'm working with an engine that has this type of piston crown, then I have the chambers in my heads reworked on a CNC to match the piston shape, then mill the heads to achieve the final squish/clearances that I want above the dome. I like a consistent .040 to .045 above the dome.
See the attached 'section' images and a sketch of the piston crown that I designed for the older Jahn's pistons - 3 5/16 diameter. I had a brand new set of Edelbrock heads reworked to fit these piston crowns. Notice how much DEEPER the piston pocket needs to be for the crowned piston shape:
Here is a sketch form my 3D Model of the Egge style dome:
Attachment 455563
Here is a cross-section view of the Egge style dome:
Attachment 455562
Here is a cross-section view of the consistent radius style dome - Ross pistons:
Attachment 455564
I've seen some engines where the installer ran into this issue and then took a big file or grinder to the tops of the pistons to "remove the crown". I'd not recommend this method . . . I believe it is best to modify the chambers - but I'm a bit of a perfectionist! LOL I've also seen folks reshape the piston tops in a lathe . . . just another way to skin the combustion chamber cat!