..I see....yes that will give a raised compression.

Ok...an out.....while you have the head in your hand, you can improve it quite a bit in the combustion chamber. That will remove material, and thus you will lower the compression at the same time.

Hear me out now...every detail...you will be saved by the bell.

First ...pings and knocks starts somewhere...its like that mysterious spot in a soda pop, where gas seem to materialize from.... magically.

Pings and knocks have a strong tendency to start in places where heat can collect.

That is sharp corners, casting irregularities etc.

First, get a sand paper and sand every sharp corner round. You will find that the mating surface to the cylinder is cut very sharp. Run your finger all along the edge of the combustion chamber and you will find a sharp edge you need to remove.

The edge does not have to be more round than the diameter of a thicker safety pin, and you will be fine on that....a round edge will disperse heat so much better and it will be avoided from being a collection spot for heat.

Ok...with a dremel tool, carefully round off inside the walls of the combustion chamber, there are ugly castings on the side walls, that needs to be rounded off and smooth...here you can be liberal in removing material, with the goal to have all, nice flowing rounded lines.

The valve seat installation tool on most any mass produced engine always leave a moat...an edge ...kind of a wall...all around the valves.

Its a sharp edge.

It does two things, its a heat collector with its sharp edge going around the valves, and it hinders flow ...the valve will sit sunk down in a little hole , and not getting up and flow properly until it has left the seat with a pretty good margin.

Remove that edge ...this might be hard with the valves still sitting there, so I would remove the valves, and with a dremel tool carefully grind off that little wall.

The...the combustion chamber... should be smooth , no edges.

(While you have it disassembled , put a dab of honey on your FU finger , and stick a sand paper onto your fingertip, and remove any casting irregularities in the ports...this pays out good)

The piston, work on the top surface only, do not work on the edges , sides or the ring area.

You can see that usually when making the dome, they make it like a facet, with different flat surfaces.

When its made by a machine , and have facets, you will have sharp edges between the different surfaces.

Make all corners and edges on the piston top, rounded off.(again..leave everything else on the piston be....top surface only)

If you also want to make it pretty, and even more efficient, you may want to polish all the surfaces to a mirror....you do that by going up in sand paper numbers once you have the shapes formed...the shine starts to appear around 600 grit....