Because the wrist pin doesn't quite quite reach the bottom ring on the piston. This allows for a more streetable application due to less chance for oil consumption to occur
ummmmmmmmmmmm. how bought just build a 383? its a 400 stroke with a .030 350 overbore. simple and effective. ford pistons do nothing been there done that. if your boring it your gonna want aftermarket pistons anyhow? your making it way more complicated than it really has to be. companies have done theri homework an aftermarket piston will fix any small issue a factory piston has which isnt much.
ive seen a 400 vortec and a 377 vortec. needless to say the 383 one blew it out of the water with vortec heads. 400 blocks arent all that great for a driver trust me on that. lower nickle content etc. if you want some super stroked out small block its possible to eceed the 4.000+ stroke mark but youll pay for it and by that time ditch the vortec system, itd be a hinderance more than anything if you go that big.
honestly not trying to be harsh but if you dont know that people have been putting 400 cranks in 350s for years and your attempting some makeshift engine with random pistons to be different id avise against it. Ive been there for fun. we made 750hp from a 307 small block in my old shop class, used ford rods and pistons, a crappy forged crankshaft from a blown up 350 and some other random stuff with a 500 shot of ntrous and a 3.8 supercharger. we blew it up on purpose to see how much it could handle, using parts that arent really made to be together might not be the best thing for longevity just saying.
also with a .030 overbore youll need a 3.97 stroke and with a .060 youll need a 3.92 stroke. ive never seen either of those unless you go full blown custom using a 350 block. still a 400 block is a poor choice.
,in a 350 block.
