454 TBI for '98 350 Vortec

[rsicard]

I have purchased a used 454 TBI for use on a '98 350 Vortec. I am at odds on which injectors to use in the throttle body. Right now it has the 17104288 injectors but am uncertain as to their condition. Need to order replacement injectors. Have ordered adjustable fuel pressure regulator for the throttle body. Have two choices of injectors, the 17104288 or the 5235231. They are as follows from what I have found on the Internet. Also ordered a Bosch higher pressure fuel pump than the stock 15psi pump. Then should be able to adjust to some value pressure that should work. May have to purchase different poundage fuel regulator springs to accomplish this. There is a Vacuum referenced fuel pressure regulator available by way of Ebay. This seems to be counter productive to use as the ECM should make the fuel corrections via MAP values.

5235231 - Red / Blue - 80pph - 7.4L / 454 - 88-90

17104288 - Pink / Purple - 46pph @13psi - 7.4L / 454 - 94-95 *NOTE: Came with 30 PSI regulator used @ 26-32psi for 67-72pph

These flow rates are a safe bet average @ 12-13psi, be aware that actual flow can vary by greater than 10% throughout production.

Any advice or comments on this and course of action would be greatly appreciated.

[dave w]

One option you might consider is having the 17104288 serviced and flow tested ($16 each) by Mr Injector: http://www.mrinjector.us/ I've had several sets of TBI injectors serviced and flow tested by Mr. Injector, I highly recommend him. On a couple occasions, I requested Mr. Injector to flow test the TBI injectors I sent him at a specified fuel pressure, usually 18 psi. Maybe have the 17104288 injectors serviced and flow tested @ 30 psi? This option is usually half the price of a single new TBI injector, but you get two serviced injectors that work like new.

dave w

[fastacton]

Since you've already ordered the pump and regulator, I'd probably go with the 5235231 injectors. You'll be able to get more fuel at lower pressure from them, which might give you a little more flexibility. I might be interested in your old injectors if you want to get rid of them.

Are you going to use a throttle body adapter or a TBI intake? The factory 454 adapters were built for the older throttle bodies, so the gasket surfaces don't match up around the idle air passages with the newer 454 TBs. You might want to build up that area on the adapter with epoxy or something if you're going that route to prevent vacuum leaks.

[rsicard]

Thanks to both Dave W. and fastacton. Dave, thanks for the referral to mrinjector. Will request that he test at 20 and 30 psi after reconditioning the injectors. With his Lb/Hr numbers at these psi's can get and idea of how they are working. Then can interpolate what would be a test fuel pressure to set the adjustable regulator at. The higher pressure injectors provide better atomization of the air/fuel mixture. Yes, replacement injectors are expensive! Again, thanks.

Fastacton, I have a Trans Dapt TBI to 4150 carb adapter. It had to have the 2 bores enlarged to maximize air/fuel from the throttle body. The same will have to be done to the aluminum 4150 Intake Manifold. Will watch carefully, the mating of the throttle body to adapter and adapter to 4150 manifold to make certain there are no vacuum leaks. Again, thanks.

[dave w]

I'm using a 1994 7.4 liter Throttle Body on my 93 K1500 / 5.7 liter engine. I bored the factory 5.7 liter intake to accept the larger throttle blades of the 7.4 liter, then used the an aftermarket adapter, see attached pic.

dave w

[rsicard]

Dave:

After boring the 5.7 liter intake, what part number injectors were used and what pressure fuel pump is being used?

Thanks very much for all the information. I have sent the injectors off to mrinjector for reconditioning with additional request to test at 20 and 30 psi and document the results and send back with the injectors.

[dave w]

Dave:

After boring the 5.7 liter intake, what part number injectors were used and what pressure fuel pump is being used?

I'm using "Cop Car" injectors 17084327. I'm using the stock fuel pressure (about 13psi) from the 93 K1500 5.7 liter throttle body installed on the 94 7.4 liter Throttle Body.

For the most part, I "Cloned" the early 90's police caprice 5.7 liter engine specifications when I replaced the engine in my 93 K1500.

dave w