Performance
Continued from Page 2

The next step was running the return line into the tank. The return tube should be within one inch of the tank bottom, ensuring that the tube opening is always submersed under the fuel level. Here, we contacted Classic Instruments, who supplied a fuel gauge sending-unit that uses a return tube as the float mechanism's mounting stanchion. Very slick. It simply slips into the stock tank-mounting hole.

Wiring Harness
With the fuel pump, filters, and lines in place, next is the wiring. We spread out the Painless Performance harness to make sense of the wires and oddball connectors that sprouted everywhere. Like all Painless Wiring harnesses, all connectors and sections are identified by small tags. Do not remove any tags until you are completely finished. Study the harness. Read the directions. Read them again; and once again. Get a sense of how it all works before you connect or snip any wires.

We mounted the ECM to the firewall with Velcro, which actually makes a very secure attachment and helps isolate the computer from vibrations.
The harness routing is contingent upon where the computer is placed. We mounted ours under the dash between the A/C evaporator and the fuse panel. Behind a kick panel is another logical spot. If you're totally out of space, Painless Wiring makes an extra-long harness for placing the computer under the seat. We mounted the ECM to the firewall with Velcro, which actually makes a very secure attachment and helps isolate the computer from vibrations.


Next, we drilled a 1 5/8-inch hole in the firewall to slip the harness into the engine compartment. This is easily the most bewildering moment. There are seemingly a zillion connectors. We carefully fished them through the hole and arranged them in their general positions. All connectors are unique to the sensor they feed. You can't connect them wrong. Making it all look neat, though, is a time-consuming process. So, take your time.

Getting Sensory
Three sensors require special attention. The MAP sensor connects to the manifold vacuum, informing the ECM about engine load. It must be mounted higher than the vacuum source with the hose connector pointing down. Painless Performance places the MAP sensor inside the car, for a clean look. Arizona TPI recommends mounting the MAP sensor within 12 inches of the vacuum source. Try it inside first. If the ECM shows a MAP sensor error, you may have to move it closer.

Continued on Page 4

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Photo Guide

Painless Wiring supplies a threaded oxygen-sensor boss to be welded into the exhaust system. It must be mounted within 12 inches of the exhaust port for the sensor to work correctly.

The vehicle speed sensor attaches between the transmission and speedometer cable. It tells the computer (ECM) the relative speed of the car.

The Painless Wiring TBI fuel injection harness includes everything you need to connect your system. The comprehensive instruction manual includes a complete list of all parts required, with GM part numbers.

This is the ALDL connector and Check Engine light. It's where you tap into your computer's diagnostic power. The computer stores trouble codes in memory, which are communicated via flashes by the light.

Painless Wiring identifies every wiring circuit and connector with small plastic flags. Do NOT remove these tags until you're finished!

The brains of the outfit: the ECM or computer. ONLY use the ECM for a 1987-90 GM pickup truck or Suburban with a 5.7L (350ci) engine. Required part number is 1227747. Wrecking yard price: $75-$100.

GM fuel injection systems require a compatible, electronically controlled distributor. Every fuel injected small-block uses this distributor, as well as some mid-'80s Camaros and Firebirds with computer-controlled carburetors. Later models mount the coils separate from the cap. Note the absence of a vacuum advance can and the addition of a 4-pin connector. Wrecking yard price: $40-$100.

The oxygen sensor reads the content of exhaust oxygen, thus measuring the leaness or richness of fuel mixture?keeping the engine running with a 14.7:1 air-fuel ratio.

On the left is the all-important MAP sensor (manifold absolute pressure), which reads manifold pressure, thus engine load. It should be mounted within 12 inches of the throttle body, above the vacuum source. On the right is the Electronic Spark Control, which feeds the distributor key data.

The GM throttle body and manifold assembly looks a lot like a carb setup.

This GM throttle body has two "bottom-feed" fuel injectors. On two-injector applications, injectors alternate so that each injector opens every other time a spark plug fires. Injectors can go a lifetime without needing to be rebuilt.

Arizona TPI supplied this fuel pump/filter/mounting kit. A pre-pump filter MUST be used?any small piece of grit or hose can damage the pump. The post-pump filter MUST be designed for fuel-injection systems, as it is under constant pressure. The pump is wrapped with foam to keep its vibration from being heard inside the vehicle.

When using a TBI intake manifold on early-style small-block cylinder heads, the center bolt holes must be machined/elongated because they go into the head at a different angle. Arizona TPI supplies manifolds already machined, ready to go.

For leak-proof fuel line plumbing, we used Aeroquip Versil-Flare flareless tube fittings and Aeroquip AQP Socketless hose and fittings. AQP hose and fittings are good for 250 psi?yet don't require any hose clamps.

Fuel return-line plumbing was made easy with a Classic Instruments fuel sender (p/n SN33), which uses tubing to mount the float/sender mechanism. We added a 90-degree fitting so the fuel line would fit between tank and trunk floor.

Mounting the vehicle speed sensor to the Turbo 350 tranny was complicated by lack of clearance inside X-member. The solution: a short, 4" cable extension that positioned the VSS outside the X-member.

The throttle-cable and transmission kickdown cables are from Lokar Performance Products. Mounting is a bit tricky because TBI doesn't use the standard carb-pattern 4-bolt mounting. We fabricated a bracket/riser that bolted to an extra threaded manifold boss.



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