Same turbo I have, S475 T4 83/74 turbine. Perfect for a big power 4.8. Should make north of 800.

 

Where did you purchase your turbo from GMCtrk?

So a Borg Warner S475 T4 83/74 with a .96 A/R? Will that exhaust housing have a 4" down pipe connection?

 

yes 4" DP connection. KB gets them from ForcedInductions

I have the 1.0 A/R. You could go with any of the options with minimal difference IMO. I'd probably go with the 1.0 or 1.1

 

Not a fan if any one company over another.
The Borg stuff is great and cheap at T6. But a 4.8L I think is gonna be laggy with a t6. Plus a t6 takes up too much room. Does not fit cleanly. Sure will make the power but max power isn't what you feel on the street.

Going Borg. With a T4. Yes.

For good power good spool.
I would do the
76/83. 1.10 or smaller ar. Even a .90 T4.
Now you have a couple of option with that 76.
Billet wheel, race cover or both. Either option helps power. But the billet wheels are lighter then the cast ones.
AR housings are cheap. So you can play with those and move the power band around.

 

Thanks for your guys' input. So the larger the AR, the higher in the rpm range it will make power? I don't want to spin this past 6500. It would be nice to make best power around 6k

 

Personally i would contact foose, he has alot of experience with making the 4.8 fast and strong. He would give you real hands on advice.

 

Funny you say that because I was just looking through his threads and the turbo he made 900+ with was the S475 83/74 1.10AR with the billet wheel and race cover. So good call guys! I wish I knew this project was going to happen when he sold it so I could have bought it from him.

 

72mm magnum is what i got on mine. still tuning but truck runs pretty solid

 

How easy is it to swap turbine housings? Do any of you guys drive around on the street with a .90AR and then swap it to a 1.25AR before heading to the track?

 

It's not hard to swap it, would just be annoying though.

And I wouldn't waste any money on billet wheel or anything. A cast 475 should be more than a stock 4.8 can handle at full tilt.