tylert14

iTrader: (11)

First off some quick specs.
383 LT1 half filled block, 4340 crank, 4340 H beams, JE -31cc pistons, ported heads (by me nothing crazy), 90mm throttle body.
1 5/8" primarys 2.5 crossover 3.5 downpipe. BIG A2A intercooler. T56, Mcleod twin disc, 3.50 rearend gears. Megaquirt engine managment LS1 coils BLAH Blah blah. Shooting to make around 700HP I have the fuel and drivetrain to support that easy.

Alright, I'm about ready to buy my turbo though. And while I'd say I'm very knowledgeable and I'm building this car specifically to be a turbo setup I'm stumped when it comes to WHAT turbo. So I'm looking for some turbo sizing help. From what Ive gathered in my quest for knowledge I've narrowed it to a few choices.

A. Garret GT40r
B. Turbonetics TC76 or TC78
C. Precision PT76 or PT78

Here is Garrets site you can see I have the choice of a 40-88 or a 40-94 with a slew of different A/Rs to choose from.
http://www.turbobygarrett.com/turbob...ochargers.html

As for precision there site is not working on my browser and I can't find much info on the turbonetics stuff. Whichever I end up getting it will be a ball bearing version. And also take into account my engine management has 2 step and Anti Lag functions I am going to use so the durability of the turbo should be a big factor as well.

Basically what my question is, which turbo would you choose, and what configuration would you get it in (A/Rs, etc). I'm open to suggestions about stuff not on my list as well! I appreciate anyone that takes the time to read this and give me some opinions!

RealQuick

iTrader: (14)

Since the heads are mildly ported (and don't flow well to begin with), you will need as much turbo to get you to 700rwhp. Out of all the ones listed, I'd go with the Precision T76GTS (not sure if you can still get the 78mm version). That will make more power than the TC turbos.

tylert14

iTrader: (11)

What is special about ther GTS series? And do you know what ARs are available and which I should get?

RealQuick

iTrader: (14)

The TC series have a smaller compressor housing for small packaging, so it will give up some HP when pushed. the 76GTS is about the best 76mm T4 with small sizing you can get. get the .96 A/r.

LASTLS1

iTrader: (7)

The TC76's are good for about 1000hp each.

Professor_speed

iTrader: (8)

a gt40 will not get the job done. the others are a toss up tc's will spool a bit faster the precisions will make more power, pick your poison.

tylert14

iTrader: (11)

LONG: So a T76GTS with a .96A/R. Does precision offer it in a divided t4 flange, open, or both? And I know precision offers a lot of different compressor covers, is it the same way for the GTS series?

SHORT: Divided or open? Which compressor cover?

tylert14

iTrader: (11)

By the way cam specs are 224 224 550 550 114LSA Compression ratio is 8.8:1

Beaflag VonRathburg

iTrader: (176)

I have a zero mile rebuilt GT4202 I'm looking to get rid of. It's a T6 flanged, 74mm with a 1.15 AR. I have pictures of it in the link in my sig. I'll shoot you a PM.

borninatransam

iTrader: (4)

Can you say hard to spool? He's going to want to stick T4 flange here and a little smaller AR. With a home ported stock set of heads he'd have to spin the hell out of it to get it to really come one. Doesn't precision offer a T4 flanged 88?

frcefed98

iTrader: (16)

383 ci should spool a 1.15 a/r very well.

hellbents10

iTrader: (10)

If 700 is all you are shooting for go with a tc76.

tylert14

iTrader: (11)

A few thiungs I wanna make note off... I want BB, mainly because I love the sound, call me gay. And this will mainly be a street car, it will see some 1/4 mile and flashlight drags though. Also I would like to keep the rpms below 6700

I appreciate the input. Right now I am thinkg 76GTS with TC78 as runner up.

But keeping all options open... What are the opinions about beaflags garret? That flange and A/R seams big for a 74mm turbo. Wouuld I be able to reach my 700hp goals with it? And how much laggier would you say it would be than a 76GTS.

Beaflag VonRathburg

iTrader: (176)

You're saying my 74mm would spool slower than a T4 flanged 88mm? The turbo I have is rated to 1000 horsepower. The PT88 is rated for more at 1200 hp.

Agreed. I'm not trying to pump this up, but it is what it is. There's a reason I chose it over something else.

Here's a guy running pretty much the exact same turbo. His is a T4 flanged GT42 76mm with a 1.12 AR where mine is a T6 flanged 74mm with a 1.15 AR.

https://ls1tech.com/forums/forced-in...lots-pics.html

fenix999

iTrader: (17)

In all honestly, just get a TC78 for what you're doing you are thinking wayy too much into it and i think its because you dont know much about turbochargers. The turbo that will probably be the easiest to package and make 700hp with will be the TC76 or TC78. Get the TC78 since 2mm bigger will not hurt you or be noticeable in spool time, it will only help alittle with power. Anyway you look at it, most of the "small frame" T4 turbos that all us LSX and LTX guys are using on mild motors will get you to the power level you are looking for and they will all generally be .96 a/r, anything smaller in a/r will be a waste of time as it will choke your setup on the top end and any larger A/R housings arent sold in that size T4 turbo. Some of the larger turbos (T6 or mid/large frame T4) will have a 1.00, 1.10, 1.15 or larger A/R but .96 would be fine for your setup and it would spool quickly.

About the BB comment, are you effing serious man you've got to be shitting me? Good luck either way...oh and for that BB comment, you might as well get the TC78 on the basis that it comes all polished and looks "prettier" haha jus messing with ya man, DO IT!!!!

tylert14

iTrader: (11)

I like my vacuum cleaner to whistle while it wooshes don't hate

SPRAYED 01

iTrader: (22)

Wait this is mainly a street car with a half filled block? Thats kinda weird.

Anyway im running a tc78. Great turbo with no lag on my 347,and its tiny and can fit anywhere. Any dont get me going on the shinny factor,lol.

fenix999

iTrader: (17)

haha lol

tylert14

iTrader: (11)

My boss has had a lot of experience half filling SBCs and the only ill side effect he's seen is slightly higher oil temps. But I will be running full synthetic after break in and frequent oil change so I don't see it being a problem. It's probably not even quite half filled. 40% fill mayby? lol

Are your numbers in you're sig with the old turbo or the TC78? If not how much power with the 78, what are you reving it to and how much boost?

I am shooting for 700 RWHP (I should have mentioned that earlier, I would have assumed I was saying at the crank how I worded it earlier)

And you're burnout vid is awesome! I hope my car sounds as good! Is that with the old turbo? It sounds like it's not laggy at all lol. Is that a Tial BOV?

SPRAYED 01

iTrader: (22)

My numbers in my sig are with the old pte 67mm. After the install of the tc78 i ran into some valve float that i didnt have time to fix last season. But on a mustang dyno it did 560rwhp @4900rpm and about 670ftlbs by 3400rpm. This was with a locked 3600 stalled auto through a 9inch.

This is 15lbs but i couldnt go over 4900rpm due to valve float,it totally fell on its face after that point. I have some patriot extremes sitting in my tool box waiting to go in.
Im also upgrading the hot side.

Alex