Concept would be to maximize the bump without the need to require grinding on the dome after the fact using an 848 casting. I have a Faro arm and plan on scanning the block, head and gasket as well as other parts to put together a 3D model of the engine with three blocks and 4 848 heads that I can scan. Getting the piston closer to the deck surface will reduce chamber volume (adding a valve pocket will add, but allow for valve clearance for higher lift and longer duration cam profiles). Every 0.010" of piston to deck height = 0.17 point of compression (calculated with a 3.780" bore size) and every CC that can be eliminated in the chamber volume increased the compression by 0.08 point. Basically adding a 6 cc dome (spread out over the available space will increase the compression by 0.50 point. Eliminating 1 cubic inch (16.3871cc's) will raise the compression by 1.54 point. If I can the the dome to bump a stock block / stock head (unmachined) to 9.5:1, that would be my goal. Anything higher I can live without for this project.
Key is not interrupting spark path, quench (or improving it) and keeping weight down. I have a set of forged 235 pistons and had a set of Jahns. Understand that only a couple companies will do a semi custom cast piston (adding dome material for you to finish machine). The rest will sell forgings (JE, Wiseco, Ross, Arias, Diamond, etc) for you to machine (I don't have the equipment for this.
