Bigger valves in stock head
Thread Starter
TECH Regular
Joined: Feb 2004
Posts: 438
Likes: 0
Bigger valves in stock head How much of a hp/torque difference is there between a cleaned up stock head with bigger valves and the typical aftermarket head. I think the OEM heads are pretty damn good as is. i would think just adding larger valves would be 90% of the hp/torque gains the aftermarket head guys see.
once you install larger valves,you have to enlarge the bowls underneath them to realize any gains.if you just install larger valves without any supporting bowl work,you can actually lose airflow/HP.look at the GMPP LS6 heads,they flow great and they use stock size valves.
Originally Posted by 66deuce
once you install larger valves,you have to enlarge the bowls underneath them to realize any gains.if you just install larger valves without any supporting bowl work,you can actually lose airflow
If you open the bowls and seats up to about 90% of the larger valve diameter then you get much more flow. Just putting in the larger valves normally increases very low-lift flow only at the sacrifice of a significant amount of high-lift flow.
Some people can get 300+ CFM from a stock head with the bigger valves when the port is reworked.
Not to threadjack, but how much of a real world difference will the larger valves make? From what I understand the stock seat can be cut to accept 2.020 and 1.570 valves. What kind of flow difference would the valve make vs. opening up the bowl to 90% of the stock valve size? I dont know if the .020 is woth the expendature of new valves, cutting the seats, and the valvejob if the difference is negligable...
Originally Posted by GuitsBoy
Not to threadjack, but how much of a real world difference will the larger valves make? From what I understand the stock seat can be cut to accept 2.020 and 1.570 valves. What kind of flow difference would the valve make vs. opening up the bowl to 90% of the stock valve size? I dont know if the .020 is woth the expendature of new valves, cutting the seats, and the valvejob if the difference is negligable...
