Good Morning Gentlemen,

I am looking for some opinions on how to build my new 413CI LS2. I ordered the short block assembly from SDPC and would really like to push the 650 to 700hp mark N/A. On top of that I will be installing a 150 shot of NOS (already already in the car on my LS6 which is coming apart) to hopefully achieve the 800 to 850hp range. Anyway, SDPC said the 413CI LS2 short block assembly is good to 900hp. A couple of friends of mine suggested I port my stock LS6 heads, install bigger valves and reuse my current Comp Cams bumpstick which specs out like this...LIFT is .584 int. / .569 exh. - DUR@.050 is .226/.226 - ADV. DUR. is .275/.279 and LOBE SEP. is 113. I would like to go bigger on the cam, although the current cam is a nice cam...streetable and makes decent power in the LS6. I am running a six speed manual so I don't really care how streetable the new cam is. Go big or go home right?! I also realize a new intake, injectors and throttle body will need to be added to the equation. Oh, lastly I already have Stainless Works long tube SS headers, no cats and and full Magnaflow exhaust system on the car. The car (which is an 04' CTS-V) ran 521 RWHP on the dyno with 125 shot on the little 346CI LS6...now its time to go big!!! Suggestions?

 

What are the specs of the shortblock? Is it re-sleeved?

With that cam and OEM heads you will probably fall well short of your N/A power goals. Going to need some serious heads and big cam (240+ duration .620+ lift) to make 550+ rwhp out of that thing. And you didn't mention what sort of intake manifold?

 

Thanks for getting back to me. The specs on the block are as follows...

LS2 Aluminum Block - 4.005 Bore - Not sleeved
Crankshaft - Eagle 4340 Forged Steel - 4.100 Stroke
Connecting Rods - Scat 6.125", 4340 Forged H-Beams
Manley - Dished Pistons 10.5 compression

Not sure on the intake yet...I was thinking of something unique and different like the Edelbrock Pro-Flo XT.

 

You need REALLY good heads to make 650whp from just 413ci, especially with a relatively small 4.005" bore. I'd look into some hand ported aftermarket castings, like a small bore LS7 head, and then a valvetrain to support about 7500 RPM.

 

I have a long stroke 421 build with decent AFR 230v2's and made 544rwhp, another 100hp's on top of that is going to be really really hard. Anything over 550rwhp is going to harder and alot more expensive to make happen.

 

I am looking for 650-700 crankshaft hp...not rwhp. Sounds like you have a pretty good combo! I would assume you are pushing the 650 mark at the crank.

 

Thanks to all for your help! With all the heads out there, it's difficult to select the right ones...would it be beneficial to just go through my stock LS6 heads and have them ported and install bigger valves? My understanding is they are a pretty decent head already....?

 

Not if you want to achieve 650-700 bhp

 

If you want 550rwhp out of a 413ci then you will need some aftermarket heads, IMO. you will probably need some AFR 230v2, TFS 235, Mast, etc Cam will need to be bigger, atleast 235/242 or something like that, maybe bigger. Mine is a 243/247.