SRTKLLR

iTrader: (1)

My plan was to use one Garrett GT-76 turbo for my Silverado with a 408 but members here 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 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 .76 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.

SRTKLLR

iTrader: (1)

Here are some pics of the turbos.

Grr

iTrader: (2)

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.

SRTKLLR

iTrader: (1)

I measured the inside opening of the T4 flange and it is almost 2" x 3". The 2" pipe being is not too small? Whet is the size of the collector on the stock manifold?

Will a merging the two 3" down pipes into a 4" y-pipe be ok?

By laggy where do you think full boost will be at? 3K, 4K etc.

I looked up the housings and they make a .70 A/R for the P-trim.

I also saw a transitional pipe that goes from round to oval that would work well to weld to the T4 flange.

Grr

iTrader: (2)

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

SRTKLLR

iTrader: (1)

Since I took the GT-76 off the Hemi I needed to replace it with a bigger one so I went with the Comp 80-79. It doesn't look all that much bigger though but I hope it works good.

Here are some pics compared to the GT-76:

mad max 777

From my understanding a single 76 mm with a .96 on 10# with a cam should give u 600 easy. I'm doing a 76mm on my 6.0 lq9 I'll let I know if it's to laggy. I doubt it will be. Ask Josh from ky turbo he is a sponsor on here.