Fuel Delivery and Air Induction: Adjustments

Removing Idle Needle Concealment Plugs:

1. Remove the carburetor from engine.

2. Invert carburetor and drain fuel into a suitable container.

3. Place carburetor on a suitable holding fixture, with manifold side up. Use care to avoid damaging linkage, tubes, and parts protruding from air horn.

4. Make two parallel cuts in the throttle body, one on each side of the locator points beneath the idle mixture needle plug (manifold side), with a hacksaw.

5. The cuts should reach down to the steel plug, but should not extend more than 1/8" beyond the locator points. The distance between the saw cuts depends on the size of the punch to be used.

6. Place a flat punch near the ends of the saw marks in the throttle body. Hold the punch at a 45° angle and drive it into the throttle body until the casting breaks away, exposing the steel plug. The hardened plug will break, rather than remaining intact. It is not necessary to remove the plug in one piece, but remove the loose pieces.

7. Repeat this procedure for the other mixture needle.

8. Using Tool J 29030B or B T7610B, (or equivalent), turn each idle mixture needle clockwise until lightly seated, then turn each mixture needle counterclockwise 3 turns.

9. Reinstall carburetor on engine, using a new flange mounting gasket, but do not install air cleaner or air horn gasket at this time.

10. Start engine and allow it to reach normal operating temperature (drive wheels blocked).

11. While idling in Drive (Neutral for manual transmission), A/C "OFF," adjust both mixture needles equally, in 1/8 turn increments, until dwell reading varies within the 25°-35° range, attempting to be as close to 30° as possible. If reading is too low, turn mixture needles counterclockwise. If reading is too high, turn mixture needles clockwise. Allow time for dwell reading to stabilize after each adjustment. Check and adjust if necessary the Idle Speed Compensator MIN/MAX, base and fast idle speeds. Repeat idle mixture adjustment. After adjustments are complete, seal the idle mixture needle openings in the throttle body, using silicone sealant, RTV rubber, or equivalent. The sealer is required to discourage unnecessary readjustment of the setting, and to prevent fuel vapor loss in that area.