Vacuum Advance Mechanism
- Set engine speed at 2500 RPM. Check for advance by disconnecting and connecting distributor vacuum hose.
- If available, connect a vacuum pump after removing distributor vacuum hose. Run engine at idle and slowly apply vacuum to check for advance.
- If advance is excessive, check for deteriorated or sagging vacuum controller. If advance is insufficient or there is no advance, breaker plate is not operating properly or vacuum diaphragm is damaged.