White05z71

iTrader: (1)

So I’m in the process of building a motor for an 04 RCSB 5 speed 2wd. So far I’ve got the short block built with a brand new GM crank, Compstar Rods, and Wiseco -11cc pistons. I have the 317s that came with the motor but I’m a little unsure if I should run those or look for a set of 799s. The truck is purely a street truck and will problem never see a track. The plan is to run a built t56 and the turbo should be here by the end of the week. It’s a BW s475 83 1.25ar t4 if that makes any difference. I guess my question is should I stick with the 317s and deal with the lower compression, or find a set of 799s and bump it up? Fueling is gone be set up for 93 and meth. Any help would be appreciated!

madmann26

iTrader: (7)

Without knowing anything else, I’d run the 799s.

You can run the 317s also. The trade-off is going to be when you’re not in boost. It’s going to feel a little lazy but you will be able to run more boost due to the lower static CR.

White05z71

iTrader: (1)

That what I figured. I tried to figure out my CR with both heads and can’t for the life of me. Tried using the calculator and must be punching in some wrong numbers

03sierraslt

iTrader: (22)

What’s your planned hp goals? That turbo should be very responsive but will choke out pretty quick with that turbine on a 6.0.

without knowing all the specs (deck height, gaskets etc ) the 317’s are gonna really drop your CR with -11 pistons. I would avoid 317’s in your case and find some 799’s or 243’s.

White05z71

iTrader: (1)

I’d like to see 650-700whp out of it. Not sure on the deck height but the plan is to run ls9 gaskets. I had a feeling the 317s would be less than ideal, but I already had them. I guess I need to hunt down a set of 799/243s. I’ve been looking but haven’t been able to find a set. Am I being overly optimistic with my HP goals?

madmann26

iTrader: (7)

You’ll need at least 10psi, maybe 14.

Over 10 you need to run e85 or meth preferably.

White05z71

iTrader: (1)

No e85 around my way so meth is already planned for.

jon1440

I'm running a very similar combo: 6.0, 317's, ls9 head gaskets. Its set up with a flex tune. 78/75 VS Turbo. the cheap one. With 20lbs boost at 13 degrees ran a 11.10 at 125. In a 2002 Silverado Extended cab 1500. Not the quickest but no slouch. This past summer it surely hurt some feelings at the drag strip. I never questioned if the engine needed more compression. If its a daily I wouldn't sweat it and just run the heads you already have. Given they're in good shape. You can adjust your tune (timing) do make it more responsive on take off. Since your going with a boosted build I'd stick with the slightly low compression heads because like most you'll eventually want to add more boost. It'll make more power easier with boost increases than it will with more compression. Plus you wont have to worry so much, up to a point, about having to run meth because your trying to avoid preignition.

White05z71

iTrader: (1)

Not too shabby. The 317s I have are good to go. I’m just hoping to break into the 10s with this setup and still have the truck be fun to drive on the street. In the spring, summer, and fall, I drive it all the time. I’m just worried about it being a dog out of boost. I also found a set of 799s local to me for $350 so I may just pick them up just in case. I’d most probably run the 317s to see how it does and if I feel the need, swap to the 799s

03sierraslt

iTrader: (22)

The 317’s are going to put your CR in the 8’s, that’s too low. Get the 799’s, don’t be afraid of a little added CR. FYI I am 9.98-1