omore001

iTrader: (1)

Hey guys, the project is finally underway and in a few days I should be breaking in my new fully built 370 iron block.

Old motor set up:
engine: LS1 alluminum 347 forged rods and pistons 10 to 1
camshaft: Comp 222/224 .565/.567 112 LSA
Heads: Stock LS1 ported with upgraded comp springs (918's?)

New Motor set-up:
engine: LQ4 Iron 370 forged rods, pistons, and crank, arp hardware, hellfire rings, LS6 oil pump 8.7 to 1
camshaft: EPP forced induction (232/240 .595/.608 115 LSA)
Heads: 317's with Patriot Gold Dual valve springs, LS7 Lifters, LS9 head gaskets

Induction: Rear mount turbo kit customized, Garret T67 with .81 A/R, front mount intercooler, BOV, and 38mm Tial wastegate, meth injection.

Fuel: Racetronix single with 5X lbs injectors (will upgrade to dual pumps and 120 or 96 injectors soon)

Transmission: 4L60E built by Transmission Physicians, 4K stall

I have done way too much turbo research, I have ask for suggestions from the tuners and the vendors and I have read up on other members builds which are similar to mine.

I have narrowed my choice down to 2 very different turbos, both with their pro's and con's.

Turbonetics TC78 w/ 1.15 A/R:
Pro's: compact and light, capable of 1000hp flywheel, reasonably priced, A direct swap on my existing turbo kit
Con's: I have been told that due to the small 60 series housing, I may not be able to make good power past 6K RPM

Borg Warner S400-80 1.1 A/R:
Pro's: great price, makes BIG power, makes power all the way to redline.
Con's: Very Large and heavy Physically, a little laggy on my set-up (does not bother me), Need to make changes to my existing turbo kit to properly install, Need to buy this with a T4 downgrade to make it work on my kit ($189).

I am open to any other turbo suggestion, however, if the turbo suggested requires changes to my existing turbo kit, I will go no smaller than an S400-80. I am leaning towards the TC78 but I will consider anything else, please post helpfully and gives reasons for your response. "Just go with a TC" response wont help me much. I need to place an order for the new turbo soon, I want to tune only one time with the new turbo as soon as the new motor is broken in, thanks guys.

TransAmcoupe98

iTrader: (10)

I would go with the step above the t67 and get the t76. Stay with the .81 a/r housing to help with spool. Should make some crazy power. You have 60# injectors in it BTW. 96 or 120 are way too big for you app. What kind of intake manifold is on it? Is it still the LS6?

omore001

iTrader: (1)

The .81 A/R will hold me back, it worked fine for you because you did longtubes unwrapped which lengthens the spool time drastically. I know someone with a TC76 rearmount and .96 A/R who did his set-up correctly with stock manifolds wrapped all the way and has a 370 similar to mine, his turbo is out of breath way before 6K with a ton of backpressure.

Yes still LS6 intake, I plan on 15 lbs of boost if I go TC78, so 60's lbs will be almost maxxed out.

mike13

iTrader: (27)

Instead of going with a TC78 maybe just the straight T78? You'd have the larger compressor or maybe the T78 race cover which is even larger.

I'd say T78 or maybe one of the GT42 type combinations, I would think you would want the larger compressor to push more air if your already talking 15psi.

mike13

iTrader: (27)

Just reread your post, are you running stock or ported 317 heads?

omore001

iTrader: (1)

Stock 317's mike, 14K on them, just resurfaced with Patriot gold dual valve springs, locks, and titanium retainers.

omore001

iTrader: (1)

T78 would be a dream, the price is holding me back though, S400>T78 in price and output. Plus I think Dr. Turbo @ Forced Inductions is going to be running a special on the S400 next month. Also the T78 would require just as much altering to my turbo kit as an S400, just for thought.

OUTLAWZ RACING

iTrader: (9)

I run a GTS76 with the .81 exhaust ar on a 4xx ci motor vic jr, patriot heads stg3 ,epp cam ect. I the most hp the car ever made was 813 710 tq. I think it mad 813 at 5.5k and drop to 780 ish at 7.1k red line. tq peak at 5k and slowly drop. my car pulls all the way to red line dosent really nose over and my rear mount is all custom. I also run stock manafolds. Power was smooth and pulls hard. i dont have back pressure issues I run a 4.5 inch dump and I have a magnaflow in the I pipe. The exhaust is 2.5 to the 2.75 I to the flang from sts.

omore001

iTrader: (1)

Thanks for your reply, I'm sure your set-up works great with the .81 A/R due to the 6-speed. (Smaller A/R's work better for spooling manual transmission equipped cars) On my old 347 set-up, with the .81 A/R, because of my high stalled Automatic, I was choking up past 6K at just 8 lbs of boost. Torque #'s took a nose dive a 5100 and HP peaked at 5300 and dropped 105hp by 6000. I am definitely getting a larger A/R on my next turbo. A 2 second duration window-switched 50 shot will cure just about every lag condition known.

mike13

iTrader: (27)

Have you thought about trying a master power turbo if your concerned about cost?

omore001

iTrader: (1)

I read many horror stories about the MP units, I know the newer ones are supposed to be very reliable, just fear being sold an older, problem prone MP unit that has been on the shelf for a few years. They have great bang for buck and I have checked them out.