hey everyone im building a 97 vortec 350 tbi for my car, im having a hard time finding any info on the correct injectors to use. ive been told anything from 305 injectors all the way to 454 injectors. please help!!! also im swapping out a 305 ive read that i need to use a 350 knock sensor why is that? thought all small blocks are essentially the same.

 

Injector sizing will be based on your HP.The stock 350 injectors will support approx 250 to 260 HP.Increasing fuel psi will raise the flow,but,the stock pump won't support much over 14 to 15 psi.You need approx 1 lb/hr of fuel for every 2 HP you make.There's a lot of info in the TBI segment that goes into more detail.You can get into the 325 to 330 HP range by installing an adjustable fuel psi regulator,better pump with the stock 350 injectors up to approx 18 psi.This will require some tuning as well for optimum results.

 

this will probably sound like a rookie question, do you combine both injectors lbs/hr and half the totally horse power to get proper injectors??

 

Basically, yes: take the total fuel flow (all injectors), double it, then multiply by .85 (85%), that is the total HP that can be supported.

A more detailed explanation can be found here:

http://www.dynamicefi.com/TBI_Fueling.php

RBob.

 

I can tell you first hand a Vortec head small block can get pretty thirsty for fuel, especially once you take that weeny little junk 191/196 @ .050, .414/.428" lift, 111* LSA, advanced 5* cam out of it.

I am feeding the L31 in the 1999 Suburban about 375 HP worth of fuel. The 23.1 lb/hr spider setup is running 91-93% duty cycle at 5,400 rpm. Only changes being a 1995 F-car LT1 cam measuring 268/271 @ .006, 202/208 @ .050, .449/.460" lift, 116.5* LSA, installed 4* advance at 112*ICL, a pair of hooker 1 5/8" long tubes with 2.5" collectors and dual 2.25" exhaust, and a Volant cold air intake. Quite frankly given the performance of the 5,200 lbs Suburban its making every bit of 350+ hp.

 

Well let me tell you what I've got for my beast. It's a 1997 vortec 350 out of Tahoe. I've had the heads ported polished and bigger valves put in. Screw in studs,Alex's parts vortec valve spring kit. Edle Brock rpm none air gap intake with 1" carb spacer tbi adapter plate ported polished tbi unit. Cam is a zz4 cam(208/221 duration, .474/.510 lift) with ls7 lifters. Bottom end is balanced polished, arp connecting rod stud kit, Keith black flat top pistons with 4 valve reliefs. Hooker shortie race headers with a Doug's y pipe to 3" mandrel bent piping to a hooker aero chamber muffler. Going to use ebl flash and wide band to tune. No emissions on engine no a/c. T56 trans with 4th gen rear end 3:32 gears. Founders rear end suspense kit. That's all I've got for her right now. Don't know if that will help any at all. Thanks for the advise!!!!

 

You need the 65lb cop car injectors, 350 esc module, knock sensor and a chip out of an 89' caprice TBI 350 cop car at the very least, or find someone to custom make you one.

 

I'm going to use ebl flash so I won't need the chip or ECM. Just plug and play with the ebl flash. I have thought about going carb to avoid the issues of tunning.

 

Leave carburetor in 20th century - it will cause more driveability issues then you can shake a stick at. EBL will take care of tuning which carb will never be able to solve. Bone stock L31 can be fed with with a pair of 61lb injectors at 20 to 24 PSI depending on your HP goals. Either adjustable FPR and or a stiffer FPR spring will do the trick in addition to upgraded FP. Stock TBI pump tops out at 20 PSI deadheaded. This assumes stock peanut cam and exhaust manifolds.

You will need your ECM - EBL is installed within your ECM. Make sure that your ECM service number is compatible with EBL

//RF

 

The cam is a zz4 with ls7 lifters and hooker shortie competition headers with Doug's y pipe into 3" mandrel bent piping to a Hooker areo chamber. So 61lb injectors with the fuel bumped up and I should be good? What are the part numbers for the 61lb injectors?? Not very familiar with tuning, I have heard that running leaner will make the car run a little meaner. But doesn't running lean create the chance to melt stuff down?????? Thanks for the help!!!

 

There are several path's you can take:
1) Commonly available LO5 truck injector 5235206 (plus other service numbers) typically flow in the range 650cc/min to 700cc/min @ 1bar (14.7 psi). This means that a 5206 (stock 5.7L) injector ranges in the low 60's for lb/hr.

2) Finding 5.7 Vortec Van specific 74 lb/hr

3) BBC 80 lb/hr at 13 PSI part number 17084304 (plus other service numbers)

1 and 3 will be the easiest approaches in your case. The only issue with BBC injectors is making sure that idle pulse width is 1.2 mSec or longer. BBC injectors may deliver more fuel than engine needs at idle. Dropping fuel pressure at idle requires VAFPR.

4) On tuning I suggest that you do a bit or reading - there are several basic EFI FAQ's posted which cover all key elements of EFI tuning. There is a learning curve - but in the end it is all worth it. Dynamic EFI website (EBL) has comprehensive articles dealing with basic tuning steps.

ZZ4 cam is Okay cam for TBI, but tuning will be required. There are better cams, but that's a subject for another discussion all together.
ZZ4 cam specs
duration @ 0.050 208/221 deg
Lift 1.5:1 0.470/0.507
LSA 112 deg
reference:
https://www.thirdgen.org/forums/tpi/...fications.html



//RF

 

not to highjack this thread , what cam are you running? GM 12551705 or a custom grind?

 

I cant remember if its 705 or 241 but it came in a 1995 LT1 F-car engine.

 

ok thanks