Tim94gt

iTrader: (2)

I'm in the planning stages of a winter/spring Turbo build on my GTO.

Current Engine Specs:

ls2 Stock Bottom End
GMPP LS3 Heads
226/232 626/626 112+2 LSA

Turbo Specs:

Compressor Wheel 78mm
.80 a/r
4” Inlet and 2.5” Compressor Outlet
Inducer- 78mm
Exhaust Side:
Exhaust Housing T-4 Flange
.96 ar Exhaust Housing
3.0″ Vband outlet
Exducer- 76mm

Using truck manifolds and 2.25 piping for hot side

Probably going to stick around 8psi since I'm on a stock bottom end. I will be using a timing cover oil drain and plan on pulling the heads to change the gaskets(Cometic 0.040 thickness) to stock thickness to decrease compression a bit. Since I'll be in there, would it be worth it to swap cams. Was looking at the BTR Turbo cams and one was pretty close to my specs except for the LSA.

Any insight on how my current cam would perform with the turbo? I don't want to spend extra money if I don't have to since I'll probably end up buying a larger cube forged short block next year.

truckdoug

iTrader: (25)

if you're only going to 8psi I'd leave the engine alone.

the cometics will not change the static CR enough to really warrant the cost and the work. and a turbo cam would only increase the dynamic CR

I'm assuming 92 pump gas, and you're afraid it'll knock at 8psi with your current CR?

Tim94gt

iTrader: (2)

Yeah, was a little worried about knock. Compression according to a calculator is around 10.6 if I recall correctly.

I'll be running 93 pump gas. I'd love to go E85, but only a handful of stations up here carry it.

truckdoug

iTrader: (25)

well I can only say what I'd do. I'd leave the motor be, since it's known to be in good shape.

Then I'd build a nice hotside around it and that 78/76. spend my money on making sure things fit cleanly. A nice, well thought out install.

Then I'd run 8 psi and 13* timing keep the AFR on the fat side and let the plugs tell me what to do. Maybe methanol injection if my intake temps get to high.

That way I could have my turbo makin choo choo noises and learning how to tune it.

You can always build a motor on the stand as a back up.

Tim94gt

iTrader: (2)

That's the plan, except for the tuning part. I have a well known tuner local to me that could do a much better job than I can. I would love to learn how to tune, since I do everything else myself, but I'd rather start with a bolt-on car and work my way up. I could always experiment with my Sierra though, haha..

I do have a 5.3 sitting on a stand, just in case I grenade the ls2.

gametech

iTrader: (1)

I didn't see valve springs mentioned. It's going to take some damn good springs to keep that cam from floating valves under boost.

Tim94gt

iTrader: (2)

I have BTR .660 dual springs

Ragna

I said to replace springs =( like the first thing I said and someone said stock would be fine..was like nah get good ones valves kissing pistons is bad..

Tim94gt

iTrader: (2)

So......What springs would you guys recommend?

Like I said, it has BTR 660 lift dual springs right now, maybe around 8-9k miles on them, if that.


To be completely honest though, if I have to swap the springs, I'd rather just do a cam swap. I'll have the timing cover off anyways, so it's not that much more work to just put a new one in.

Ragna

I am using those springs for my twin turbo build so they should work fine. I wouldn't sweat it, id just check one spring for tension or pressure whatever its called to make sure they are not weak and roll with it.

truckdoug

iTrader: (25)

I cant imagine btr duals floating at 8psi unless that was really hard 8000 miles

gametech

iTrader: (1)

Now that we know what springs are there, I don't see any problem either.

Tim94gt

iTrader: (2)

Thanks guys, I appreciate the feedback. I guess I'll just run this cam and see how it does. can't wait to start the build, have to practice my welding a bit more before I start, but should get the project rolling mid-late winter.