Hello all. I have just bought a 2006 LQ9 with 78k. I'm going to be swapping this into my 1998 BMW M3 and need help specing out a top end. I'm looking to have some where between 450-500whp thru a LS2 T56 6spd. This car is going to be an all around toy.. it will be put thru Drifting, Drag racing, & street beating.. I could car less of the manors on the street as long as it does not stall out i don't care how aggressive it is.

Here is a list of what I'm thinking of going with please leave your feed back.

Heads/Springs/valve's Package: From Texas Speed - PRC LS3 and L92 CNC Ported Heads
- PRC LS3/L92 CNC Ported
- PRC .650" Dual Spring Kit
- Valve Options
-- 2.165"/1.59" Standard GM Valves
-- 2.165"/1.59" Stainless Steel valves
-- 2.165"/1.59" GM hollow stem intake valves
-- 2.165"/1.59" Stainless Steel hollow stem intake valves


Intake / Throttle body:
- Fast 102 LSXR LS3 Intake
- PTM 102mm Cable Driven Throttle Body


I need help with the above head package and what Cam/Rockers/pushrods to go with. I'm also trying to stay away from having to cut Valve reliefs into the pistons.. as i don't have the tools to cut them or measure the Piston to Valve Clearance.

I have been reading on here to Mill L92 heads .015 and run .040 head gasket's.. but i don't know what that translates into as far as Combustion chamber CC's


Thank you all for any advice / guidance that is given.

 

Are you completely committed to the LS3 heads? Those big valves have shrouding issues in a 4" bore and as you mentioned the big valves can cause clearance problems. Since you want max effort, I'd get a pair of Trick Flow CNC 225 cathedral port heads. Check out some of the cam kits available at Tick Performance.

 

not really committed to the ls3 heads but I've been reading some of the other LQ9 / LS3 head builds on this sure and I did not see anything about shrouding issues.. I'm not sure if I completely understand what that means.As for the piston to valve clearance, the cam specs would effect that.

Edit...

I just checked tick performance and they list a CNC ported ls3 head for the 6.0 truck motor.

 

i ran a fully bolted 6.0 lq9 with LS3 heads without any shrouding, 480+ on the dyno ET says over 500+, definitely go with the hollow stem valves, keep the valvetrain as light as possible, stock rockers with trunion upgrade, it'll save you from disaster in the upper rpm range only thing on this setup i was limited to a 231/239/624 cam ! but it got the job done


ive got my LSXr intake for sale with a nixtrous express direct port system set up for a 200 hit if interested

 

There is a ton of info about the valve shrouding. Remember, LS3 heads were designed for a 4.065" bore. Skeet, you have it and don't realize it. What that means is the big valves actually impede flow because they are so close to the cylinder wall. Does the LS3 heads fit on a 4" bore? Yes. Will they make more power than stock heads? Yes. Are there better heads for a 4" bore? Yes.

 

my bad youre right i had my heads worked before running them, youre talking about stock heads untouched i do recall some issues, my heads were CNCed then hand ported, numerous times on a flow bench to get actual air to uniform around the valve

 

We'll if I can't go ls3 heads without a bunch of work. What head do you all recommend that could get me around my power goals.

 

a CNCed set of heads from texasspeed ( badass cnc program ) will get the job done, but also a nice set of 243/799 thoroughly worked with proper setup ( cam intake flow ) will also get you there, it takes money, its all gonna be in the way its setup, and to make sure its setup right, im talking overall build, have a t56 will help out a lot on reaching your goal

 

TEA has the best flow numbers:

Total Engine Airflow | Custom Cylinder Head Assemblies Tallmadge | Airflow Development | Custom Cylinder Head Ohio | TEA Total Engine | CNC Porting | Cylinder Heads | Cylinder Head CNC Porting | Ohio | :: Total Engine Airflow ::

Do a search over at LS1tech, there are a couple threads where people pulled the LS3 heads off and went with Trick Flow heads. They made more power. With my LS1 GTO, I swapped out ported 243 heads for Trick Flow 215 heads and made over 20 hp more.

 

Which ever is cheaper lol doesn't make sense to spend extra 500-1000 on a set of heads for maybe 10-15 more hp at the crank. IMO

Plenty of people making 450 with cam and ported 243/799< these should make more tq on a 6.0 then L92s also