hey all, let me start by giving you a run down of where i stand in my project and also where i would like to go.
first off i dont own a truck but you guys seem to be the most knowledgeable of all the truck based ls engine forums that i wanted to post here.
my car is a 71 datsun it started out as a ls1 with a single 72mm turbonetics turbo and a 6 speed, it ran a best of 10.2 at 138 and made 500 whp on 8 psi and 93 octane.
i took out the ls1 and put in a ls6 and upgraded the turbos .60 ish ar housing to a .96 still with the restrictive q trim and it made 600 whp on 93 octane and meth at 11 psi and went 10.00 at 144.
next i replaced the 6 speed with a built 2004r and it went 9.78 at 138. this brings us to this season.
i pulled the ls6 and bought what i thought was a 5.3, i also purchased a precision 74mm turbo with s trim turbine to replace my old 72mm . my goals are 700 whp on pump gas with meth. in tearing down the 5.3 last night i found out its a 4.8. its from a 01 silverado and does not have the catech heads ( or however its spelled ). i guess at this point the junk yard wont exchange it since i tore it down so i figured i should probably try and see if it can make the numbers. based on what hot rod mag did and what i see on here i think it can do it. so far i plan on gaping the top ring, adding katech rod bolts and arp head studs along with ls9 head gasket. for the cam i was going to either swap over the cam and lifters from the ls6 since they only have about 4k on them ( it was a new crate motor ) so ls6 lifters and cam with some hardened push rods of stock length.
this is as far as i have got. im looking for suggestions and critiques on my build, i do not have access to e85 so pump and meth will be all i have. im looking to run 9.50s or better and make around 700 whp, i will be getting tuned by steve at tuned by frost in virginia so the tune will be done by one of the best. supporting mods are twin 255 pumps, aeromotive fpr, 60 ib injectors and stock ls1 rail. also a stock ls1 intake and tb. i do have the ls6 heads but research shows milling them makes them thin, i dont really have the budget to get the 4.8 heads ported and upgraded to larger valves but will if its required. also am willing to run a different cam such as the one hot rod used. any way here is a photo of my old set up and a video of my best pass. please feel free to comment and i look forward to all the help i can get, i plan on having this finished over the next two weeks.

New best in the 240 9.79 - YouTube

 

If you are referring to the twin turbo 4.8 build where they tried to blow up the engine then I would select a different cam. They chose that cam because they were shooting for the highest possible hp number which I don't think would necessarily transfer into the best track time. For the time being you could stick in a ls6 cam (~$160 used) and then have someone spec you a turbo cam when you eventually get your heads worked on.

 

my self i would run the ls6 heads as they are. also do you have the ls6 intake? looks like a fun build.

 

Im curious why you lost 6mph when you went to the 200r4, were you bouncing off the rev limiter at the end?

 

im kinda curious as to why youre swapping the engines?

 

I'm guessing this is a track car? You are going to have a significant difference in spool time going from 5.7 to 4.8, and moving to an S trim will only further that. Track only should be ok though if you can get out of the hole. If it were mine, I would leave the rod bolts and the ring gap alone. Lose the LS1 intake and swap to a NNBS 90mm intake and TB. Go with LS9 gaskets and ARP studs like you have planned. The LS6 heads would be better with the larger chambers for what your shooting for, they would allow you to run more boost with more resistance to detonation. I think you could reach your goals with this setup.

 

didn't think about clearance on that intake, maybe you could run an LS2 with a 90mm. I would assume it would outperform the LS6 also

 

i would cantact stock48 on here. he specs a lot of cams for turbo apps and with plenty of solid results. also, im sure foose04 could help ya with some stuff as well. his turbo 4.8 truck is deep in the tens ...

 

update. got a bunch done, the bottom end was in rough shape as far as being all stuck and gunked up , i spent a few hours cleaning every piston and ring and wrist pin so they would move properly. i did gap the top ring while at it and reassembled everything with the original bearings and what not. i also swapped everything from the ls6 valve train over including the oil pump and timing chain and gears. i decided to sell the ls6 heads and 4.8 heads and get some texas speed 2.5 stage cnc ported 862 castings with pac springs installed also got some ngk 7 plugs and ordered a few ods and ends like gaskets and what not to button it up. i wouldnt mind upgrading the intake but the power gains are so small on boosted cars the cost isnt worth it. so the ls6 heads the ls6 block and the 4.8 heads are for sale if any one is looking you can pm me. i will take your advice and maybe try and contact those guys to see what they think.

 

no definitely not a track car lol, daily driven with full interior stereo and leather seats ect ect. oh i failed to mention above that i did go with arp studs and ls9 gaskets as well.