Cant decide on which heads to go with this build... I hear all of em are great heads but what would be best for my setup?
05 LQ9 stock bottom end
Holley High ram intake
Custom turbo cam depending on which heads i get
80lb injectors
Twin 67mm turbos
Plan on only boosting 12-15psi
It is going on a 91 single cab pick up which weighs around 3800lbs and I daily it everyday,I go racing every weekend(mostly roll racing) but do go to the track everyone once in a while. Right now I have a t56 magnum with 4.10s but as soon as I boost it, I believe I'm going with 3.42s or 3.73s. I just want a good reliable setup since it is my daily...

 

For those mild goals, I would just use the 317's that came with the engine. Throw some ls6 hollow stem/sodium filled valves and some good springs in your stock heads and have fun.

 

Which 67 mm turbos have you sourced for your build? In the process of looking for a set of twins myself.

 

Can you please explain why you would recommend those valves for this application?

 

So 317s would be best? Trying to get the most power with whatever head is best for my setup on 12-15 pounds... Might throw a 100 shot on top just to hurt some feelings lol...

 

ls3 style heads are a ton better then 317s but not worth the extra expense unless you already have them.

 

http://www.hotrod.com/how-to/engine/...re-port-heads/
317 vs. LS3 on a 408 with the compression and cam selection favoring the LS3, and a overbore to help the LS3s that your setup wont have

If you look at the flowbench numbers the LS3s flow like 20-25% more but when you go looking for results the peak difference falls to 6-7% and the rectangles are down below 4000rpm even with the test stacked in their favor. This might be perfect for boost or light cars that can't use lowend but don't buy into the LS3/L92 are magical period that is too often spouted.

If you can keep the rpm up or get it into boost quick enough at a roll that can all be fine, just understand it.

Oh and GM seems to agree with the LS3 being down on lowend, look up LS6/M6 axle gearing compared to LS3/M6 axle gearing.

I don't think 3.42s/M6 and rectangles would be good unless you can build boost before the start.

Have you seen the cathederal intake test HotRod did? Looking at the graphs I would choose the TBSS intake all day long over the Holley unless you can keep the motor over say 6000rpm.

My vote would be say 3.73s with the 317s a TBSS intake, take the money saved on heads and intake and put it into methanol injection.

I should say I have never played with boost though.

 

I run a sb lq4 cam only with 317s and tbss intake. I built my own front mount crossover with a s480 t6. It drives around pretty good out of boost. I have had better heads and cam in my last setup in sig. This one has no where near the power out of boost but damn if it dont pull hard when boost comes in!! I start making boost around 2800 rpm. With this new setup i put together myself im pretty happy with it. I run a 4l80e and 3.73s as well. Traction is an issue tho lol.

If u already have 317s id run them. Alot of guys make big power on them and there easily available and cheap.