Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Ignition Timing
Ignition timing is checked or adjusted with engine at normal operating temperature, distributor vacuum line disconnected and plugged, transmission in Neutral and engine at normal idle. On "P" models, use number two cylinder and timing mark tab on bottom of cylinder.
| Application | Man. Trans. | Auto. Trans. | |||
|---|---|---|---|---|---|
| 350" 2-Bbl. | 0°TDC | 8°BTDC | |||
| 350" 4-Bbl. Fed. Light Duty | |||||
| Suburban | 6°BTDC | 12°BTDC | |||
| G-2500, 3500 Rally | 8°BTDC | 12°BTDC | |||
| All Others | 8°BTDC | 8°BTDC | |||
| 350" 4-Bbl. Cal. Light Duty | |||||
| Suburban | 4°BTDC | 6°BTDC | |||
| All Others | 4°BTDC | 8°BTDC | |||
| 350" Heavy Duty, All | 4°BTDC | 4°BTDC | |||
| 454" Light Duty, All | (1) | 10°BTDC | |||
| 454" Heavy Duty, All | 8°BTDC | 8°BTDC | |||
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.