I recently bought a holley projection setup with the 670 cfm throttle body. I was wondering if I were to somehow modify and use larger injectors, like around 100gph, would 670 cfm be enough to support 450 horsepower, and could I try porting and polishing the body to try and pick up some cfm? Anyone ever done this, and if so how much did they pick up? And could I still use the compuuter that comes with it. Any ideas or suggestions would be appreciated.

 

I dont even think they make 100 gph injectors.

 

As far as 670cfms, that's large enough air flow for a 350 atleast. If you compare it to carbs they usually recomend a 650 to a 700 cfm carb for a strong 350, so theoreticly it could support 450 hp. 670's come with 85 pph i believe, most people switch back to stock injectors with holley tbi's cause most don't need that much fuel.

 

Actually the holley 670 comes with a variety of injectors. The two most popular are the 502-5 w/ 57pph injectors (advertised for 305s) and the 502-6 with 65pph injectors (advertised for 350s). If you look though, you can find more options such as the 502-4 w/ 45pph injectors. The largest injectors holley makes are 85pph rated at 21 psi, though I think holley underates their injectors. There are a few guys running the 670 on their 330hp 350 H.O. engines with success, though any higher than that is unproven.

 

Ok..........I just was thinking that if a 670 cfm carb could work on an engine making around 450 horsepower then a tbi could if it used bigger injectors, or reworked on the throttle body. I would really like to know if anyone has had any luck doing this on the two injector system.

 

The main difference between a 4bbl 670cfm carb and a 2bbl 670 cfm tbi is that they are rated at different inch hg's. So in reality, 670 cfm on the 2bbl tbi is more comparable to a 550cfm carb.

 

Closer to 475cfm when converted to 1.5" of Hg, thats why you see TPI throttle bodies that flow 1000cfm.

4BBL = 2BBL/1.414

So with 450hp you be in the 4BBL TBI range.