yesd0g

its called inertia, (I think I spelled that right?!?) the weight of the valve, including the retainer gets banged open when the cam lobe hits it. if its lighter the spring can slam it shut faster as it follows the cam lobe profile. if its lighter, you wont hit valve float as soon, which = higher rpm limit. ohh ya, when you break a retainer, you suck a valve, and your engine goes boom in a bad way.

ProzacOverdose

yes yes...very true yesdog....but to go fast and cheap.....pr4(LS) rods shot peened w/ arp bolts on some aftermarket pistons with a thicker head gasket. oh yeah...new rings...this will last you 200 plus hp....and its WAY CHEAPER then anything else.