General Motors — Cam Angle Verification and Adjustment
Adjustments · HVS Distributor
From a General Motors service manual — check it applies to your exact model before use.
Before you start
- The ignition timing cannot be adjusted; the distributor may need adjusting to prevent crossfire
Procedure
- With the ignition OFF, install the scan tool
- Start the engine and allow it to idle to normal operating temperature (Cam Retard Offset not accurate below 1,000 RPM)
- Increase engine speed to about 1200 RPM
- Using the scan tool, monitor the Cam Angle Offset
- Cam Angle of 705 degrees indicates the distributor is properly adjusted
- If not 705 degrees, with engine OFF slightly loosen the distributor hold down bolt
- Start the engine, raise speed to about 1200 RPM and monitor Cam Angle
- For a negative reading rotate the distributor counterclockwise; for a positive reading rotate clockwise
- Repeat until 705 degrees is obtained, turn ignition OFF
- Tighten the distributor hold-down bolt to 3 N·m (25 lb ft)
- Start engine, raise speed to 1,000 RPM and recheck Camshaft Retard Offset
Tools required
- Scan tool Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Distributor hold-down bolt: 3 N·m (25 lb ft)
- Cam Angle Offset: 705 degrees
Source: General Motors service manual. Steps and values are as documented; always cross-check against the official manual and any later revisions for your exact serial number before servicing.