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Bored&Stroked · 03-10-2026, 08:45 AM

Obviously the dome radius changes as the diameter of the piston changes. If I am correct, I believe Ross sets the dome radius based on the height of the dome itself - which is usually .187".

So, one could easily calculate the CNC radius to work with and use a 1/4" ball mill with a fine step-over to mill the chambers in the head to match the pistons. You can then use a hand air tool to polish the chambers to get rid of the toolpath marks.

The critical thing to first understand is where does the pin need to be (compression height) to get the piston dome where you want it.

One could decide to have the piston edge "above deck" the same amount as the gasket thickness (regular gaskets tend to be about .052" thick). If you popped the piston up to the top of the gasket surface (via pin location), then you would know exactly how deep the dome in the head needs to be.

One more thing to note is whether or not your block is relieved and if so, what is the relief depth. This is important in that you may want to move the ring pack down a bit (if you have a heavy relief) so that the top compression ring doesn't get too much heat into it. I do this on custom piston orders and I also specify metric ring packs.

03-10-2026, 08:45 AM	#19
Bored&Stroked Senior Member Join Date: Jan 2011 Location: Central Ohio Posts: 5,906	Re: Crank stroke before 49 Obviously the dome radius changes as the diameter of the piston changes. If I am correct, I believe Ross sets the dome radius based on the height of the dome itself - which is usually .187". So, one could easily calculate the CNC radius to work with and use a 1/4" ball mill with a fine step-over to mill the chambers in the head to match the pistons. You can then use a hand air tool to polish the chambers to get rid of the toolpath marks. The critical thing to first understand is where does the pin need to be (compression height) to get the piston dome where you want it. One could decide to have the piston edge "above deck" the same amount as the gasket thickness (regular gaskets tend to be about .052" thick). If you popped the piston up to the top of the gasket surface (via pin location), then you would know exactly how deep the dome in the head needs to be. One more thing to note is whether or not your block is relieved and if so, what is the relief depth. This is important in that you may want to move the ring pack down a bit (if you have a heavy relief) so that the top compression ring doesn't get too much heat into it. I do this on custom piston orders and I also specify metric ring packs.