got a question, got 19lbs injector what fuel pressure do i need 2 bump it up 2 to get it to run at like 22lbs injector?

 

About 60 psi IIRC. Only thing is I can't remember the exact pressure the TPI injectors are rated at. I think I remember it being 43.5 psi where it flowed 19 lbs/hr.
SQRT(New PSI/Old PSI)xInjector Size

 

thanks for the info. so do u think i could get away with 19lbs injectors at 60psi to run a 350 motor?

 

You will be holding the injectors open longer than you should. And I'll bet that you will kill your fuel pump in short order.

Why would you want to do this?

 

Changing pressure has nothing to do with changing the pulsewidth. The higher pressure will make your injectors identical flowing to the 350s. I have done it on several TPI swaps to 350s in the field. As far as killing the pump, many GM vehicles of the era ran the similar fuel pressure and used the same pump.

 

This is interesting news! Can you give an example of a vehicle that ran 60psi factory w/ this pump?

I swapped in a Walbro pump when I did my LS1 swap but kept the Delco TPI pump...if the above is true, I have a useable spare.

 

I don't know about the fuel pump or anything.....but I *hear* that running high pressure behind small injectors makes the car harder to tune, should you decide down the road you need a computer tune...... Causes idle "particularities"....

And also, I keep hearing too much pressure will burn the injectors up prematurely, but I don't see as how increasing the pressure behind them will hurt them...... I'd love to get an explanation.

 

You can run 19s on a 350, but not at 60 psi. You most likely find that the engine might like 46, or 47 psi. Years ago my 355 got to use my 19s from my previous 305, and they worked fine.

 

Astro, Blazer, Safari, Jimmy, S10 Truck, Cyclone, Typhoon. Basically anything with the 4.3 and CPFI. It takes 50 psi JUST to open the poppets on those engines. The fuel pressure spec is 58-64 psi. (Typhoon and Cyclone are standard injectors but operate against BOOST). Also some of the small 4 cylinder turbo cars (don't quote me on year or car) ran the same pump and around 55 psi when the system was under boost from the turbo. I can't remember what the GN runs but it is up there pretty good when the turbo is boosting as well, fuel pressure regulator increases fuel pressure1 psi for every 1 lbs of boost. If you actually looked at some of the pumps they are the same guts just different terminals and outlets on some. The TPI pump and the Astro pump are identical on the inside. The wiring is different.

On a side note I helped convert an early 90s chevy blazer to a 350 Vortec. The fuel pressure spec for the 99 vortec 350 is 60-66 psi. A stock AC delco replacement F-body TPI pump went onto the TBI suburbans sending unit and provides that fuel pressure without any problems.

 

True for 1992 - 1999, including the 5.7L
In 1992, General Motors introduced a very unique fuel injection system on its 4.3-liter Vortec V6 truck engine. Dubbed Central
Port Injection, or CPI, the system looked and functioned much differently than previous designs. "The CPI system utilizes one main injector that pressurizes six plastic tubes housed in the intake manifold". Each tube terminates in a spring-loaded poppet valve that supplies fuel to its corresponding cylinder. The main injector is pulsed twice per crankshaft revolution, with pressurized fuel opening each poppet as system pressure approaches approximately 48 psi.

I'm using the Walbro 255 Lph with 30# injectors on my '88 IROC-Z 388cid, no problems.