TT Setup Help

My plan was to use one Garrett GT-76 turbo for my Silverado with a 408 but people said the turbine side was too small and would cause high back pressure so I decided to make it a twin setup instead. I pulled the GT-76 from the Hemi and need to make all new hot side piping along with the cold side.

The engine is a 408 with 9:1 cr and a 224/231 .595/.595 114 cam and I will be using the stock exhaust manifolds. It has AFR 225's and the stock intake manifold with a 78mm TB.

What size piping should I use for the hot and cold sides? 2", 2.5", 4" etc.

What A/R should I go with? Currently one has a .96 and the other is a .81. So I can change one to match the other or change both to .70, 1.15 etc.

What size WG and BOV?

Do you think the turbos are too big for my setup and I should just sell them and buy two smaller ones or one big one instead?

My original goal was to make 600rwhp and work my way up to 800rwhp slowly.

If anyone wants to trade there turbine housing for one of mine let me know.

Anyone?

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Originally Posted by SRT10KLLR

My plan was to use one Garrett GT-76 turbo for my Silverado with a 408 but people said the turbine side was too small and would cause high back pressure so I decided to make it a twin setup instead. I pulled the GT-76 from the Hemi and need to make all new hot side piping along with the cold side.

The engine is a 408 with 9:1 cr and a 224/231 .595/.595 114 cam and I will be using the stock exhaust manifolds. It has AFR 225's and the stock intake manifold with a 78mm TB.

What size piping should I use for the hot and cold sides? 2", 2.5", 4" etc.

What A/R should I go with? Currently one has a .96 and the other is a .81. So I can change one to match the other or change both to .70, 1.15 etc.

What size WG and BOV?

Do you think the turbos are too big for my setup and I should just sell them and buy two smaller ones or one big one instead?

My original goal was to make 600rwhp and work my way up to 800rwhp slowly.

If anyone wants to trade there turbine housing for one of mine let me know.

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Something you probably have no idea about or overlooked, those stock manifolds are going to cause a great amount of heat.
I'm not talking about a little wrap here and there, I'm talking when it's 100deg outside, you can say goodbye to any wiring, plastic, electronics that are within 8 inches of the manifold!!!!
Your underhood temps will be so damn hot you won't believe it!!

Trust me on this one, been there done that. I'm only warning you once lol, twin turbo setups using stock manifolds produce a sh!t load of heat!!!
For some reason, using a single setup like I offer is fine, going twins, yikes!
So wrap wrap wrap all the parts around the manifolds as well as the manifolds.

-2.5" is fine for the hotside, there won't be much hot side, just a small length of 2.5" going from the manifold to the turbo.
-with that engine, .96 a/r is fine, so is .81. I use .96 on my 408 with low compression and twins, using stock manifolds.
-I run twin 38's and it's just fine, it wouldn't hurt to go 40mm or 60mm, but my 38's work fine and hold boost and it's very steady.
-bov, just get a 50+mm bov, single before the throttle is fine.
-no, the turbos are fine ,the engine needs them! i ran T60's for a while, the truck is stronger with T76's.

good luck,

i guess i didnt awnser your questions correctly last time u called me so why dont u do it again ........ 76mm will make alot of power itself... twins will make twice your goal .... I have been slammed the last few days but i have a couple of hours driving tomorrow and i will call ya

i dont have any problems with heat... bu then again it hasnt been HOT out yet

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Originally Posted by sprayedenali

i dont have any problems with heat... bu then again it hasnt been HOT out yet

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was it just a rumor that i heard you burnt your harness? lol don't matter what setup, cast iron holds heat! it's gonna get hot!

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Originally Posted by farmtruc

was it just a rumor that i heard you burnt your harness? lol don't matter what setup, cast iron holds heat! it's gonna get hot!

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the battery cable fell onto the downpipe..... which cause it all to short out and burn up. had nothing to do with underhood temps....

oh good, glad it wasnt something major

it was something major! haha. my engine compartment was glowing red on the side of the highway... every ground wire in the harness was BRIGHT orange. but i got that all figured out now and havent had a single problem since then. :thumb:

Twins are cool. :)

Quote:

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Originally Posted by farmtruc

Something you probably have no idea about or overlooked, those stock manifolds are going to cause a great amount of heat.
I'm not talking about a little wrap here and there, I'm talking when it's 100deg outside, you can say goodbye to any wiring, plastic, electronics that are within 8 inches of the manifold!!!!
Your underhood temps will be so damn hot you won't believe it!!

Trust me on this one, been there done that. I'm only warning you once lol, twin turbo setups using stock manifolds produce a sh!t load of heat!!!
For some reason, using a single setup like I offer is fine, going twins, yikes!
So wrap wrap wrap all the parts around the manifolds as well as the manifolds.

-2.5" is fine for the hotside, there won't be much hot side, just a small length of 2.5" going from the manifold to the turbo.
-with that engine, .96 a/r is fine, so is .81. I use .96 on my 408 with low compression and twins, using stock manifolds.
-I run twin 38's and it's just fine, it wouldn't hurt to go 40mm or 60mm, but my 38's work fine and hold boost and it's very steady.
-bov, just get a 50+mm bov, single before the throttle is fine.
-no, the turbos are fine ,the engine needs them! i ran T60's for a while, the truck is stronger with T76's.

good luck,

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Thanks, I got almost the same advice from another member so I know it is sound advice.

Here is what he wrote "hotside piping 2" in and 3" downpipes
coldside 2.5" into a single 3" will be fine
wastegates small ones will be fine, 38mm or so whatever you want
BOV JGS 50mm or 60mm, or Tial Q
Turbine housings i would go with the .81 so you only have to buy 1. The .96 would be too laggy..Even with the .81's its gonna be laggy but should make 7-800whp on pretty low boost numbers. yes the 2" would be perfect,will help with spool alot. you can form them to the T4 or get whatever you need to for a cone or transition readily. Merging the 2 3" DPs into a single 4" would be ideal unless you can fit a 5", then that would be even better!

With that big of a turbine wheel you could get away with the smallest housings availible and not have back pressure issues. With the .70 housing,(which i beleive is divided even) would net 5psi probably around 3400, the .81 would be around 3800 in my guesstimation."

Quote:

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Originally Posted by casey23

i guess i didnt awnser your questions correctly last time u called me so why dont u do it again ........ 76mm will make alot of power itself... twins will make twice your goal .... I have been slammed the last few days but i have a couple of hours driving tomorrow and i will call ya

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I have been on the road myself but got back in last night. Call me anytime as I don't want to bug you at a bad time.

Quote:

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Originally Posted by Turbo6.0L

Twins are cool. :)

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Yeh, I have your single kit which is what I was going to use but not I have to make it a twin kit, lol.


Here are some pics of the GT-76 I have for the Silverado and the GT-76 I took of the Hemi(Black coated turbine housing - Left).
http://i47.photobucket.com/albums/f1...TTTurbos01.jpg

http://i47.photobucket.com/albums/f1...TTTurbos02.jpg

I had to replace the turbo in the Hemi so I got a Comp 80/79(Right).
http://i47.photobucket.com/albums/f1...CompTurbo3.jpg

http://i47.photobucket.com/albums/f1...CompTurbo2.jpg

http://i47.photobucket.com/albums/f1...CompTurbo4.jpg

I already talked to the guy who made the custom headers for the Hemi and he will be making me the twin piping soon.

For now I just installed a Nitrous Outlet plate kit so that should hold me over for a little while, lol.