Quote Originally Posted by clementeunknown View Post
Your comparing oranges to apples. If 862s flow better than old school iron heads from the 60s & 70s then with a valve upgrade should help out a lot.

PRC 220cc 5.3L Stage 2.5 CNC Ported Heads

A good P&P job and you buying the valves from e-Bay should run under $1K. The suggestion I made is for the budget minded. Besides if your gonna spend a ton of money to make a fast 4.8 a 6.0 is probably come along and eat the 4.8 for dinner and with less money.
increasing size of valve isnt everything with flow. also for the price you jsut mentined you could find a set of ported heads from a manufactor for that price

the sbc heads needed a valve increase since they werent a good design as todays. increasing the valve has shown to hurt. TSP has mentioned this a few times on ls1tech