inkis4ever

Im debating between running a big single or smaller twin setup. From research so far if I went single I would be leaning toward a pt88. I havent found much info on twins. Im considering a pair of these T76 0.68 A/R P Trim.
The motor is an lq4 ported 317's not decided on cam, forged rods and diamond pistons. It will be backed with a 4l80e trans. Im concerned about the 0.68 a/r being too low and choking the engine. Any input or suggestions would be great. Thanks guys.

98Z28CobraKiller

iTrader: (17)

Twins are easier to package in a tight space like the front of a late model Fbody. The twin T76's with the .68 a/r housings will work great for a good all around street/strip warrior on stockish cubes. It will also spool a little faster and have the potential to make more over all power than the PT88.

The down side to the twins is that it requires more plumbing and is a more complicated setup over all. This makes issues more difficult to diagnose and will likely make for a more expensive kit.

TurboS10

iTrader: (12)

Twin T61=PT88H which is a T88 compressor.

Two numbers to look at on the turbine.
A/R and exducer/outlet size.

A .96 a/r GTS (75mm) will not flow the same as a .9 a/r 111mm.
A/R is area divided by radius. Many ways to get same a/r.

Twin p trim (65mm) will support around 1400 fwhp. So twin T61 p trim .68-.81 a/r will do about 1400 fwhp.
Assuming 355-390 CID.

You didn't say what you wanted for power or use so hard to give an opinion.

TurboS10

iTrader: (12)

I know of one guy that ran 8's w/a 400 and twin MPT70 p trims.
He swapped to T76 p's IIRC and didn't like it and went same or slower ET.

Twin 76's is way more than a stock head/crank build.

Stock48 on here runs 9.7's at ~5200lbs 4x4 6.0 with a GT76.
That's basically a 7685 T4 setup. IDK what compressor cover he has. Either GT45 or GT47.

inkis4ever

Sorry guys shoulda been a little more specific. Basically what Im looking for is around the 700-800 rwhp range. And yes the motor is a 370ci. I would like to be in that range without working the turbo or turbos to death, and also have room to grow if I so choose down the road. The car will mostly be street driven a couple days a week but taken to the track maybe 3 or 4 times a year.
I know the 76's are pretty large for twins but also a little small for a single. The only reason I was looking at these 76's is due to the .68 a/r which I think would make them spool fairly quick. If they were .96 a/r 76mm then that would be def overkill for my build right???

98Z28CobraKiller

iTrader: (17)

They will work. If you look on the fast list at the top of the page, BonnarLS1 has twin TC78's w/ 81 a/r exhaust housings on an LS3 (6.2L) and they work fine but are just a touch laggy on the street. He's only pushed about 15 psi thru them so far. Those same turbos came off LS2Formula's car and ran 7.8's behind a 422 LSX. With the smaller .68 housing on a 76mm, it'll work great on the 6.0 , be responsive and should take a long while to outgrow. You can run 600 rwhp or 1400+. Just depending on how willing you are to beef up the supporting mods in order for the setup to survive the power and ofcourse, testicular fortitude.

inkis4ever

would I be better off instead of t76 twins going with t67's with a .68 a/r? Or just say screw the twins and go with a pt88 .96 a/r? Im really undecided. I know the twins will be more expensive and probably a bigger pain to tune as well. But ya gotta love the holy sh*t factor of popping the hood and seeing twins.

98Z28CobraKiller

iTrader: (17)

If I had the money and not class racing, i'd do twins and I'd just do the 76's. Provided everything is mechanically sound, the tuner doesn't care if it's twins or a single.

inkis4ever

Awesome thanks for the responces guys. 98z28cobrakiller your def making me lean toward the twin 76's. So if the tc78 with .81 a/r is a bit laggy the 76 with .68 a/r should be a bit more responsive. Im also not looking to rev the hell out of the engine to hopefully get a reasonable amount of life out of it. I would say Id like to run in the 6500 rpm range.

98Z28CobraKiller

iTrader: (17)

That's fine. You just have to have the correct converter.

inkis4ever

Im pretty fortunate in that I have a friend who I tattoo and he owns a shop, so I get his pricing on all my parts and we trade out for labor. He def knows how to build a quality setup for me but I will have to look elsewhere for a tuner. But overall he will be saving me a substantial amount on many of the parts and also any fab work that I wont be doing myself.

inkis4ever

Do you have any suggestions as far as a cam and converter? Something for both that will have good street manors also with the cam I would like it to be streetable of course but still have a "cammed" lumpy sound

TurboS10

iTrader: (12)

Twin 61's will do what you want and spool faster.
But they aren't big enough to go 7's..

61-76 can have the same size compressor housing....4x2.5.
No one will know the difference with the air filter on.

TC w/66-78 come with a 68mm turbine.
The smaller compressors are either 65, 62, 5x.

For a mostly street car with your HP goals, 61-66mm twins is how I'd go.
6162's .81 exh w 4x2.5 compressor to be specific. 6165's for more top end.
INTMD8 did 800rwhp w/T56 with 6165's on a GenII w/ 218/218 115 cam.

inkis4ever

damn decisions decisions. I think Ill talk to the tuner for some input as well. I just did some research on theturboforums and after researching there Im going to go with 98z28cobrakiller and do the twin 76's with the .68 a/r. Apparently hotrod mag did an article with a 5.3 and the same spec turbos and made over 1200hp. So a 6.0 with a pair should have no problem putting down 7-800rwhp. Oh and if its ok with you 98z28cobrakiller I might pm you here and there with some ???'s. Thanks for all the input guys. Build thread coming soon.

2000RATA

At the risk of hijacking this thread, thank you TurboS10. The 6165's are exactly what I was sold when posing the same scenario when I bought my twin kit. I wanted 900 rwhp possibility with 98% street nasty. With being a street mostly car I wanted it to have no lag if possible. I also read a guys post here with twins who made 1300rwhp with .68A/R. Easier to get exhaust through 2 exhaust housings.