Twin turbo build help..
 

I'm currently in the middle of a twin turbo build/swap from a 383 on my '69 Camaro and looking for some advice/suggestions. I'll start with what I have for the swap.. A completely stock LS1 out of a '99 Camaro and a T56 out of an M12 '04 GTO. I made the same mistake as most and wasn't originally planning on going with a boost set up and also bought a set of TFS 220 heads that were milled to produce 11:1 compression with Mahle pistons and factory head gaskets.

My goal is to get to around 650 hp. What I'm trying to figure out: Should I sell off the heads for lower compression, do I need to do anything to the bottom end of the LS1, what turbos would be ideal/recommended, and what's recommended for the rest of the conversion (ie fuel set up tank pump injectors, transmission parts, wastegates, blow off valves, should I upgrade my intake and throttle body, etc.?

I'm no expert, but most definately you're going to have to strengthen the bottom end with twin turbos. That's if you want to make real power and run boost above 8 or so pounds. I would like to think with two turbos you want to make some brute power and a stock end wouldn't hold up. So, you'll need a forged rotating assembly. Without a forged bottom end, 10-12 pounds will be too much boost on a stock crank, rods, etc. Also, if you can get a good price on the heads sell them, make sure you lower your compression ratio with the right pistons as well. Sounds like it'll be a sweet setup.:cheers:

You say you are in the middle of the swap but it appears you have not bought any of the turbo stuff yet ? Speaking from experience I would change plans and do a Eaton style blower.

What's the advantage/disadvantage?

quicker throttle response, alot less underhood heat, alot less plumbing and associated costs, easier to make it all fit. I just think it will be alot easier to get to the power level you want to be at and I love these LS engines with the blower on them. They work great with no drama.

I'll second Charlie's suggestion. Eaton blowers look great and perform great as well.

To build this engine to your power goals, go ahead and get forged pistons and better connecting rods. Go with 6.0 liter style heads. Ported 317 heads will work great and you can go with a mild port job to keep costs down. Get a blower cam and 1-3/4 primary headers and you'll make you goals. I suggest a head change simply because better heads would really help the build, and should you ever remove the blower, you can put 5.7 liter heads on the engine and regain your current compression. Your goals are easy. You can make this level of power with 8 psi no sweat. Hell, I've done it with 5.5 psi and LS6 heads.

EDIT: Just reread your original post and realized you already own great heads. Go ahead and pick up some lower compression pistons. Shoot for 10:1 psi if not 10.25:1 With forged pistons you'll be fine. Speed Inc is in Illinois and they can help you for sure if you're wanting to contact someone local for advice and maybe parts.

What about the crazy high incoming air temps associated with eaton style blowers? What is the fix for getting the IAT numbers down? And heat soak?

The heat management issues with turbos will be as big or probably a bigger problem than IAT's with a blower. I know Mark Stielow's latest car had very good IAT's in real world conditions.

Turbos are way more bad ass though!

Turbo or blower, I'd get that compression lowered. We've built a couple of blower setups on top of stock LS6 motors (10.5 compression), and max power was seriously limited by the amount of timing we could use before hitting knock retard. With ~6 PSI boost, we were hitting knock retard at just 9 degrees advance at max volumetric efficiency (in the 3500-4500 RPM range). Just my opinion, I'd shoot for about 9.5 (which, incidentally, is about where the LSA and LS9 are).

That brings up another point, which is that I'd use an ECU which has provision for knock sensing, like a GM, Mast, or Holley. Detonation can destroy a boosted motor very quickly, and you don't want to worry about a tank of bad gas causing 5 digit rebuild costs. With knock sensing, you can tune less conservatively and still be more protected.