| What are my options? It is highly recommended that anyone upgrading to a 3.4 engine either retrofit their 2.8 TBI with 4.3 injectors, or install the Holley TBI. The 4.3 injector retrofit is very easy, and is usually substantially cheaper than purchasing the Holley unit. Why is it necessary? The 2.8 TBI is equipped with 33 lb/hr injectors, and the computer "pulses" the injectors at a rate commensurate with the 173 ci displacement. The idea is to keep the air / fuel ratio as close to 14.7 to 1 as possible. The computer can adjust for variences from engine to engine and different driving conditions, but the 3.4 is more adjustment than the computer can ideally acheive. As a result...driveablilty problems, such as hesitatation and stalling in open loop, are common with 3.4 engines running stock 2.8 TBI's. Installing the 4.3 injectors (45 lb /hr injectors) solves these problems and improves overall performance by allowing the injectors to flow more fuel using the same BPW (band pulse width) that is programmed in the 2.8 ECM. Running the 3.4 engine with 2.8 (33 lb/hr) injectors can cause a dangerously lean condition, especially at RPM's above 4000 beacuse the A/F mixture is far too lean than what is required. How do I do this? You have several options. 4.3 injectors are available from several vehicles in salvage yards, such as selected 1988 and up S-10's, Astro Vans, and Impala / Monte Carlo cars. My 4.3 injectors came from a 1988 Astro, and were installed into my 1987 S-10 Blazer 4x4 with a donormaro 3.4. The total cost of the salvage injectors + TBI rebuild kit (gaskets, O-rings, ETC) was less than $50. Installing the injectors in the TBI is straigtforward. If you have ever rebuilt a carb, you will probably find this much easier. Make sure you clean the injectors prior to installation (do not immerse them in solvent!!! Injectors are electrical parts!) Also, use new gaskets and O-rings (lube the O-ringes with ATF...the sequence of installation is CRITICAL). Both the Haynes and Chilton service manuals do a pretty good job of explaining the installation of injectors. New injectors can also be purchased from most parts stores for between $65 and $115. I would reccommend specifying injectors for an 88 Astro, but many other vehicles will be equivilant. TBI Rebuild Kit -- Gaskets: I used GP Sorensen kit # 96-5410 ($32 at Autozone and likely available many other places). This includes everything you need to completely reseal the TBI, + an new fuel pressure diaphram. Why not just buy the Holley? Basically, cost. Lots of these injectors are available at salvage yards, the installation is straightforward, and overall cost is minimal. The Holley TBI will give you larger throttle bores, but their benefit is debateable, considering restrictions created by the stock intake manifold. With all that said, several members of the board have purchased and installed the Holley unit with success. Caution!!! This mod is intended for 60* motors running a 3.4 (207 ci) displacement. To my knowledge, no one has tested retrofitting a stock 2.8 engine with the 4.3 injectors. My guess is this would cause a possibly substantial rich condition. Members of this board and one other have generally reported their fuel economy to have dropped by 1 MPG or less. This is an acceptable trade off for the performance enhancements and problems solved. Written By:John Bryson (General GM) | 
