Dropped a valve on my 5.3 and instead of patching it up, I've decided to put a 6.0L under the 112 radix. Engine is out of an '04 2500HD pickup and the long block will be stock except for the cam, springs etc. I'll swap out the stock cam for the Comp in my signature with the new springs (not 918's). Engine will have long tubes and true 3" dual exhaust. Basically the same setup I have now with 6.0L instead of the 5.3. I have a 3.1" pulley on the radix now. It makes 9psi and puts out about 420rwhp. What size pulley would you suggest on the new engine? I know there is a point where you just make more heat and very little more HP. Any thoughts on HP potential? Help appreciated.

 

generally its agreed that the 2.9 is the best combination for power and not to much heat. some people use the 2.75 but its been said that it spins the blower to much causing premature wear and higher temps. i run the 3.0 on my lq9 and see about 7.5 pounds.

 

ive got a 2.75 that Ill trade ya for your 3.1

 

I had a 3.0" on my LQ9 and saw the same 7.5psi that sirk saw. Estimated hp was ~ 530-540 crank hp based on track times and weight.

 

So what caused the vavle issue? Spring failure?

 

The spring broke at the top. Just about exactly 1 coil from the top. Retainers came loose and the valve dropped. It's stuck about a half to three quarters of an inch down. Pretty common for the 918's to do this from what I've heard.

 

If you daily drive it alot, I'd go with a 3.0" pulley. If you race it more often, I'd go with a 2.8" pulley.

 

I think I'm close to 500 crank hp now. Are you saying I'll only pick up 30 to 40 hp going with more cubes, better flowing heads, and a smaller pulley? I was hoping for quite a bit more.

 

Having spent too much timwe on the heat issue I can tell u that u shud experiment with overdrive crank and blower sizes. If ur IAT's stay reasonable then get it up into the low teens of boost. If u can't find the HP/Boost/pulley combination thats working for u then u can add Meth (like me and many others have done), and that will allow for more timing. Otherwise, go to the MP122 or Turbo. Lastly, tho the stock 6.0l is stout and can handle lots of forces, if u upgrade ur cam and or heads, its the best investment and easiest way to gain all the ponies ur looking for...u can even port the stock heads. Before u put the motor in, these changes are pretty easy to make for $2-2500 for a head/cam package and less if u port what u have. R/

 

I'm not looking for a max hp motor. I know there's more power to be had by changing to a turbo or bigger blower. Just trying to get the max out of the setup I have now while maintaining reliability and effeciency. I think I have a cam (in signature) big enough to satisfy anything the radix can fill. I have a Snow boost cooler to cool things down a bit. I run windshield washer fluid through it. Forgot to mention in my initial post that I have a 90mm tbody and modified J tube coming from WCCH. Will porting the 6.0L cylinder heads do any good when I'm at the Radix's air moving limits anyway?