I have a question for you engine building guru's. I am building a budget iron block 6.0 to put in my 2005 1500 RCSB Z71. It currently has the stock 5.3 with headers, full exhaust and 4.56 gears. I am purchasing a 2003 LQ4 longblock with only 22,000 miles from a local salvage yard. I have a Vengeance VRX3 cam that was pulled out of my CTSV. I have purchased a low mileage set of Patriot performance 317 heads with 2.08/1.57 valves that have 64cc combustion chambers and a set of 1.7 scorpion rockers. I also bought a set of LQ9 rods and pistons that look brand new. I could easily reuse the LQ9 rods and pistons, but put in new rings. The question I have is, would it be worth boring the block to 4.03 and buying new pistons to unshroud these oversize valves, or will the 4.00 bore be enough. The question is boring to 4.03 bore be worth the cost to make the additional power with these heads or not? Has anybody done something similiar and know what the power gain would be versus the cost? Thanks for the help in advance, Charles.

 

Come on guys. Somebody else has got to have been in this situation besides me. Give me some opinions.

 

I would not think you would have any power loss there is alot running the l92's makeing good #s and they have 2.16 intake valve. worth the cost i would say no but bigger is better.

 

The main reason I asked the question was because these heads would be shrouded pretty bad on a 3.9 bore, but OK on a 4.0 bore. I was wondering since the 3.9 to 4.0 bore made such a difference would an extra .030 be that much of an additional help. Thanks for the reply.

 

I would run the stock pistons in the 6.0,put the 317 heads on it, use the cam, and reuse the stock rockers off the 5.3 in the truck instead of the 1.7s. The piston to valve clearance is safe that way. If you updrade to the LQ9 pistons then you loose PtoV clearance. What year are the LQ9 rods? The newer ones are stronger that the stock LQ4s. The motor would make a good torque curve w/ that set up.

 

The rods are the LQ9 rods. Same as the LS2 factory I beams with the flat top pistons. The 317 PP heads have 64cc chambers welded and recut to 64cc versus the 317 stock 72cc. If have to flycut the pistons, I will. I want the compression around 11 to 1 to get the torque for the truck. Also, what is the advantage of running the 5.3 rockers over the 1.7 scorpion roller rockers?

 

Stock are lighter.

I am not a big fan of Scorpians anyway and since a buddy had two break a couple years back. He switched his stockers back on and no issues since.

 

That is kind of strange, when I look at them in the box, they look to be of good quality.