Really cool program fun to play with doesn't have a few things such as intake runner volume on the heads, combustion chamber size, deck height, piston design, as well as rod length, quench, rocker style/ratio, more intake selections, spring pressure, oil pan design, gear/belt/chain drive, accessories, exhaust size and header design, ignition curve, ect. But hey what can you expect for free. Still a fun program to mess around with thanks for the post. Makes me wish I went with the 434 instead of the 383 but hey now I have an excuse to start building another engine. Interesting that it says going to a single plane wouldn't hurt my tq. curve it would also raise my peak tq. by 20 and give me 40 hp.