bigger valve ?'s

[TURBO 6]

Is it worth installing the bigger valves in stock heads (1.77)? How much should you gain? TIA!

 

[UNGN]

According to a test published in the GSCA news letter, the larger intake valves were worth approximately 3% more flow than stock valves.

Since HP is roughly proportional to airflow, on a 400 Hp motor, the larger valves could be worth 12 HP.

The Cost difference is about $60-100 for machining the larger seats and $100-120 for valves.

The cost would be somewhere between $10 and $20 per hp gained. You can calculate for your self if this is "worth" it, vs. other mods you can perform with your money.

 

[KEVINS]

I have also heard that the chambers and cyl bore shroud the larger valves too much to be worth it...

I have different head flow #'s on my Tech Page in my sig so maybe see if there are some flows that you can compare...

ks

 

[TURBO 6]

Thanks for the info. I think the cost would not offset the performance gain, IMO. I was thinking with my turbo (45a) I could use the bigger valves, but if it's not worth much hp I may not do it.

 

[Intercooler]

It is worth about 30 CFM on a flow bench. You can unshroud the valves enough to make it worth it and opening up the bowl under the valve is where you will see the gain.

 

[steve hughes]

With just bigger valves i don't think you will see enough to be worth it. Bigger valves and porting the heads will make a difference. With a large turbo should really make a difference.

 

[FJM568]

If you were running a 4.1L motor, it would help alot...The cyls are a larger diameter so you wouldn't run into the shrouding problem like you do with the 3.8L...

You will see as much gain by doing some bowl work and lowering the short side radius in the runners...Don't make the runners larger, you will lose some velocity, but just clean up the bowls and lower the short side radius and crank up the boost!!!