Valve Seat Recession
Symptoms
Gradual loss of compression, rough running, tapping noise from the engine that gets worse over time. May develop a misfire.
Cause
The Grey Motor was designed to run on leaded petrol. The lead in the fuel provided a cushion between the valve face and the valve seat, preventing metal-to-metal contact. Modern unleaded fuel eliminates this cushion, and the soft cast-iron valve seats wear, the valves gradually recede into the head.
Fix
The cylinder block needs to be machined to accept hardened valve seat inserts.
This is a machine shop job, the block must be removed from the car.
Budget $800-1,500 for a full valve seat insert job.
Alternatively, use a lead replacement additive (Valvemaster or similar) in every tank of fuel.
This is a Band-Aid solution but it slows the recession significantly and is adequate for cars that aren't driven daily.
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