I have been doing some research on turbos to see if I could find that elusive magic deal on forced induction for my engine. Then engine is a 383 with Pro topline Vortec Heads. I ported the exhaust side (basically cleaned it up) nothing crazy. The intake side is supoosedly 180CC but I have not verified. I am running modified TPI (I know it is not optimum, but it looks cool). The cam is a crane powermax roller cam, from memory INT 222@.050 EXH 230@.50 Lift INT .509 and EXH .528 LSA 112 Short Block Forged Wiseco -5CC block Machined with pistons .010 below deck and Felpro FP1030 Approx 9:1 compression, Scat Rods, and Eagle 5140 crank. Splayed four bolt block. Originally built to be supercharged never did, now thinking turbo SO I found a GT4294-01 Not sure what the 01 stands for. It has a different looking exhaust housing with an internal wastegate. After doing my own calculations and running some online calculators, I think the GT4294 would be a nice turbo, the only problem is this particular unit has an A/R of 1.44. From what I know so far this is pretty big. This is not an everyday car and it is a six speed to boot. SO even though the A/R is rediculous will it work? Or would I never get boost unless I was on the interstate. Also is there anyway to modify the A/R with creative machining and welding. Thanks for any input

If the turbine housing is divided, you can close off one of the sides for faster spooling.

According to the math, in stock form it should spool at 4000 - 4500 RPM on your 383ci. Closing off one inlet will make the turbine too small. Efficiency also goes down. If you can build an electronic circuit to control it then it may be worth it. If not, I would wait for one with a 1.01 or 1.15 housing. The 1.44 A/R turbo doesn't seem like that good of a deal for a small block. That is also assuming T4 flange.

Is it a T4 inlet flange or a diesel inlet flange? Have you priced out other housings for it?

It is a T4 inlet flange. I have not priced out other housings for it.

What math did you use to determine when the turbine should spool? If you could point me in the right direction. I would be extremely greatful!

lb/min air_out = lb/min air_in + lb/min fuel

The thing is that you have a 383ci with a good amount of N/A torque so on the street you have a good engine w/o the boost. Once that thing hits 4000 - 4500 RPM it will really come alive with boost. It all depends what kind of characteristics you are after.

That unit has heavy hits and the price is getting up there. I bet there is a lot of activity in the final minutes. View count is high and has been right from the beginning. It happens to all the Borg and GT units.

If you do come across a "deal", be careful where you ask questions because sometimes you end up advertising it.

No deal there. It went for over $800. Just as I figured, the activity was high at the end by the looks of things. For $800 you can get a turbo better suited to your application.

I agree. I take it that most turbo deals come from ebay. I maybe still able to pick one of those up for a good price though. I am not sure what generation of CAT motor a 3176 is, but if parts are still on hand, I happen to work as an engineer for the aformentioned company, I may be able to find something sitting around.

I still don’t think I’m following how you get from there to that it will spool at 4-4500rpm…, unless you’ve got a turbine map somewhere for it, and then I’d still be surprised if a 1.44 A/R would spool that fast.

Garrett has the turbine map listed with the compressor map on their website. That is the turbine map that I used.