I was doing some math for a 393 with 85% VE at no more than 6000 rpm's at 75* and looked up a T70 and it looks like it will fall in the highest island from 10-20#...does that sound right? I think I did the math right, only wanting 650ish to the wheels, but I thought this turbo would be too small...think it will work?
Jesse

 

If you use two of them, I'm no expert but that small of a turbo will cause a lot of back pressure on a 393. I'm using a T-76 on a 351w and I think thats borderline.

 

i agree 100%

 

It'll work just not to 6k. More like 4500

 

I calculated at 10# the engine will need 50# of fuel and that falls right in the top island...am I doing something wrong here?
Jesse

 

Get a t70 map and use MS Paint to show us where you think this engine is going to match up.

 

The problem is on the turbine side. The thing is, yes it will WORK, but it will NOT be correct. The turbine is way to small. The pressure ratio would be through the roof.

 

OK, figured it out. Was mixing numbers. 20# is 65 lb's on a 393 and that puts it on the next island down from the peak island. On a T72 it puts it right on the peak island.
Jesse

 

Again, the issue is turbine size, you need to size the exhaust side correctly. A 393 produces a LOT of exhaust especially with a set of good flowing heads.

 

two 70's not one, as everyone else is telling you, that great boost threashold that you'll get from a single t4 housing will absoultly destroy any mid and top end efficiency because it will be a cork, you might as well put a 671 roots blower on there because it wont be choked by a restrictive exhaust