Holley 502-3 Guide

THROTTLE BODY
P/N 502-3 (1985 1/2 – 89 GM Truck 2.8L V-6 Engine) 400 CFM
P/N 502-4 (1986 – 89 GM Truck 4.3L V-6 Engine) 670 CFM
P/ N 502-5 (1987 – 89 GM Truck 5.0L V-8 Engine) 670 CFM
P/N 502-6 (1987 – 89 GM Truck 5.7L V-8 Engine) 670 CFM
P/N 502-7 (1988 – 91 “S” & “T” Trucks 4.3L V-6 Engine) 670 CFM
INSTALLATION & ADJUSTMENT INSTRUCTIONS
INTRODUCTION
Congratulations on your purchase of a Holley throttle body! Holley Performance Products has written this manual for the
installation of the Holley throttle body. Please read all the WARNINGS and NOTES. They contain valuable information that
can save you time and money. Should you need information or parts assistance, please do not return the unit to the store
without first contacting technical service at 1-270-781-9741, Monday - Friday, 7 a.m. to 5 p.m. CST. By using this number, you
may obtain any information and/or parts assistance that you may require. Please have the part number on hand of the product
you purchased when you call technical service.
WARNING! To preserve the warranty, instructions must be read and followed thoroughly and completely, before and
during installation.
NOTE: Holley Performance Products cannot and will not be responsible for any alleged or actual engine or other damage or
other conditions resulting from misapplication of the throttle body described.
NOTE: Prior to and after installing your new throttle body, manually operate the throttle lever to check for binding or other
malfunction. Also, make a visual inspection of the throttle body, to look for bent levers, etc., or any other shipping
damage.
REMOVAL
1. Remove the fuse marked “fuel pump” from the fuse block. Start the engine and allow it to run until the fuel supply remaining
in the lines is consumed. When the engine stalls, engage the starter for three seconds to ensure all the pressure is
relieved. DO NOT turn the key to the “RUN” position until the installation is complete.
2. Remove the air cleaner. Remove the air cleaner spacer from the top of the throttle body. This spacer will be used on the
new throttle body.
3. Mark and remove the remaining vacuum lines from the throttle body. Remove all the electrical connections from the TBI.

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4. Disconnect the throttle linkage and cruise control linkage from the throttle lever. Remove the transmission kickdown cable
from the throttle lever (if equipped). Save all linkage clips. They will be used on the new Holley unit.
5. Remove the fuel lines from the TBI. It may be necessary to loosen clamps located away from the TBI in order to remove
the lines from the fittings. Remove the fuel fittings from the TBI. These will be used with the Holley TBI.
6. Remove the TBI and the base gasket from the intake manifold. Place a clean shop towel in the manifold opening to prevent
any foreign material entry into the intake. Clean the gasket surface of any remaining gasket material. Remove the towel
after cleaning the flange surface.
INSTALLATION
1. Install fuel fittings on the Holley TBI. Fuel fittings should be torqued to 22 ft./lbs. Remove the 1/4-20 bolt. Install the stud
(supplied) and 1/4-20 nut (supplied), torquing to 48 in./lbs. Use non-permanent Loctite on the air cleaner studs.
WARNING! Not properly tightening the air cleaner stud can lead to a fire hazard, which in turn can lead to property
damage and/or personal injury.
2. Loosely install the TBI on the intake manifold using the new base gasket provided. Be sure to install the air cleaner base
gasket. Reconnect the fuel lines to the TBI using the new O-rings provided. Torque the TBI bolts first to 6-8 ft./lbs. and
then torque the front TBI bolt to 10-12 ft./lbs. Do not reuse the TBI flange gasket. Always use a new gasket when
reinstalling the TBI unit.
3. Reinstall the electrical connections, except for injectors, and vacuum lines to the TBI. Be sure that the vacuum lines are
connected to the proper tubes and electrical connections are aligned and snapped together tightly.
Figure 1
Figure 2

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4. Cut the (4) injector wires about 12” from the factory injector connectors. Strip 1/4” of the insulation from the wires left on the
vehicle. Connect these to the wires on the harness adapter assembly by using the butt connectors provided. If all wire
colors match one for one, connect them. If they do not, see Figure 3. The white wire needs to go to ONE of the pink or red
wires. MATCH the remaining wire colors with those on the vehicle.
5. Reconnect the throttle linkage. For vehicles equipped with cruise control, reconnect the linkage, and secure it with a clip.
Reconnect the transmission kickdown cable (if equipped).
Figure 3
IMPORTANT: The TV cable must be readjusted in order for the automatic transmission to shift properly. Depress the metal
lock tab on the adjuster and hold on. Pull the cable through the adjuster away from the TBI. Release the metal
lock tab. Depress the accelerator pedal to wide-open throttle. The cable will self-adjust.
6. Reinstall the fuel pump fuse.
7. Cycle the ignition key from the “OFF” position to the “RUN” position several times, keeping the key in the “RUN” position for
three seconds each time. Check the fuel connections for leaks.
8. Reinstall the air cleaner spacer and the air cleaner. Use the new gasket provided.
9. Use a fuel pressure gauge to verify that the fuel pressure is 12 psi for 502-3, 502-4, 502-5, 502-7, & 502-8. The fuel
pressure for the 502-6 should be 11 psi. Start the engine and let it reach operating temperature.
10. Unplug the idle air control unit (IAC).
11. We suggest adjusting the idle to 700 RPM or desired RPM (the throttle adjustment screw is located on the opposite side of
the TPS).
12. Reconnect idle air control unit (IAC).
13. Turn the key to “ENGINE OFF” and adjust the TPS to .65 volts.
14. Start the engine and let it run for several seconds. Shut off the engine and recheck for fuel leaks.
NOTE: The on-board computer has adaptive memory; therefore, performance characteristics may change after a few days of
driving.
NOTE: The on-board computer may have stored codes caused by the previous TBI malfunction. If it is necessary to clear
these codes, disconnect the negative cable at the battery for 30 seconds. If the “CHECK ENGINE” light comes on,
consult the vehicle’s service manual and follow the diagnostic recommendations.

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Holley Technical Support
P.O. Box 10360
Bowling Green, KY 42102-7360
Phone: [phone]
Toll-Free Phone: 1-866-GOHOLLEY
Fax: [phone]
For online help, please refer to the Tech Service
section of our website: www.holley.com
199R9813-5
Date: 1-10-11