FastKat

iTrader: (10)

I have heard before that smaller valves give you more low end torque and that larger valves are better for running top end. Has anyone seen this first hand in their LS1 build? Also, do the larger valves really make a difference higher in the RPM band?

I am building a turbo engine and currently have a set of 6.0L heads with the larger valves than the regular 5.7L LS1. I have not installed them yet and for these reasons I am not 100% sure I want to!

Thanks, -Dave

FastKat

iTrader: (10)

To the top - anyone?

FastKat

iTrader: (10)

Is this a solid question or what?! I always thought this was one of the fundamental parts of picking heads?!

GuitsBoy

iTrader: (4)

Well, im not sure of the specifics in a forced induction application, but the rule of thumb is that port velocity is what keeps low end torque up, while overall port flow is what pulls up top. Smaller intake runner volumes and valves are one way to boost velocity but may well choke off some top end, while larger valves may air in top HP production they may make the car very mushy down low. A properly done head will balance on the knife edge where both sides are optimized.

redtail2426

iTrader: (10)

i believe your theory would only apply to a NA application.When using forced induction the rules change a bit.If it was me i would us the larger valved heads,even if it was NA.with the lsx engines you want to make as much top end 4k and up as possible for racing applications,and with a turbo i am thinking thats what your looking for.A turbo is built for top end and larger valves will help.

Beast96Z

iTrader: (21)

It depends on if your bore is large enough to unshroud the valve or not. You want the air to be able to come off the intake valve and disburse evenly into the cylinder. If the valve is to large, and the bore is to small, the air will come off the valve and immediatlly be hindered by hitting the cylider wall. Alot of it has to do with the valve job. If you have the room to effectivly use the valves, a larger valve should move more air, thus providing more power across the board, not just top or low end. The whole key is keeping the velocity up in the port. Any skilled head porter should be able to use a larger valve to his advantage, but you do have to take the motor it is going on into consideration.

whitt1

6.0 and 5.7 LS1 heads have exactly the same size valvea in stock form.Late model 317 6.0 heads have larger chambers 71cc vs 66cc and better porting similar to a LS6 head.