Intake Manifold Vacuum

Note: Before performing the manifold pressure test, check the following:

• Ignition timing
• Correct idle setting

Tools required

• Vacuum gauge
• Timing light
• MUT-II hand-held analyzer or compatible RPM meter
• Vacuum hose 3-way adapter

Procedure

1. Test timing and idle settings first.
2. Install the 3-way vacuum hose adapter as shown.
3. Plug the vacuum gauge into the 3-way adapter.
4. Start the engine and check vacuum at idle.

Vacuum limit: 400mmHg (15.75 inHg) @ idle

(verify printed p.22 vs p.29) — the summary table in Section 8 (printed p.22) lists two engine-split values, 450mmHg (17.72 inHg) and 470mmHg (18.51 inHg), instead of this page’s single flat 400mmHg (15.75 inHg) limit. This is a direct conflict between two source pages; confirm the correct figure against the printed page before use.

Note: For low readings, check for vacuum leaks or misadjusted valve lash. Check valve lash and set to specification (see Section 8).