No, zero deck does a couple things. Like CP said again, the math is easier...lol. Second, there is less wasted space above the top ring (this area never burns and doesnt produce power. So the smaller it is the better) Third, the piston is designed for a certain height deck surface. Mopar factory maching is crap. If it was flat, it was good enough. That's why the "10.5:1 compression" ratings are a joke. It also has a side effect of keeping everything else correct when the decks are parallel to the crank and flat. When the decks were originally milled, they were cut on a milling wheel. Because it's a wheel, the center will always be cut deeper than the edges, as the milling head has to be angled, or the cutters will hit as they pass accross the surface and they may chatter. It's not much, typically in the .0015" range. But I've had blocks with decks where the center was .017" taller than the blueprint spec, one edge of one end was .024" taller, and the opposite corner on the opposite end was .029" taller. These had been "milled" during a "performance build". The RB wedge blueprint spec is 10.725 IIRC, and I think one out of ten or so I've used was even in the 10.72? area. Most are 10.74+ from the factory. So you buy a good forged piston, the deck is milled flat, and then put together, and your ) deck just went to recessed .015+. If you were building for quench, that would be a problem. Which is why every engine I do, regardless of size or output, gets the mains align honed, and the block square decked to the height I need. The better block equipment now uses the main bore centerline and the camshaft bore centerline to index the decks. Old millers use a machinists level and someone's eye.
