FJ / FE / FC

Oil pressure drops below 20 psi at idle when hot. Knocking noise from the bottom end, particularly under load. May also develop a deep rumble at idle.

The Grey Motor uses plain bearings (babbit metal shells) for the mains and big ends. After 70+ years, even well-maintained engines have worn bearings. The oil pump is a gear-type unit that also wears over time, reducing oil flow.

A bottom-end rebuild, new main bearings, big-end bearings, thrust washers, and an oil pump rebuild or replacement. The crank should be checked for wear and reground if necessary. Budget $1,500-2,500 at a machine shop experienced with these engines. The Grey Motor is simple to strip and reassemble, a skilled home mechanic can do this in a weekend with the engine out of the car.

Gradual loss of compression, rough running, tapping noise from the engine that gets worse over time. May develop a misfire.

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.

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.

Engine stalls, won't restart, or runs inconsistently. Fuel starvation symptoms, the engine dies under load but may restart after sitting for a few minutes.

The mechanical fuel pump is driven off the camshaft and uses a rubber diaphragm that perishes with age and modern fuel blends. When the diaphragm fails, the pump can't draw fuel from the tank.

Replace the fuel pump diaphragm (rebuild kits are available, $30-60) or replace the entire pump ($80-150). An aftermarket electric fuel pump mounted near the tank is a common upgrade, it provides more consistent fuel pressure and eliminates the mechanical pump as a failure point. If fitting an electric pump, add a fuel pressure regulator to avoid over-pressuring the carburettor.

Hard starting, rough idle, flat spots on acceleration, flooding (fuel running out of the carby), black smoke, poor fuel economy.

The Stromberg carburettor's internal components, needle valve, float, accelerator pump diaphragm, gaskets, all deteriorate with age. Ethanol in modern fuel attacks old rubber seals. Jets can clog from fuel residue, particularly if the car sits for extended periods.

Rebuild the carburettor with a rebuild kit ($50-100 if you can source one). These are simple single-barrel carburettors that can be stripped and rebuilt on a kitchen table. The challenge is sourcing genuine Stromberg rebuild kits, they're becoming scarce. Some owners convert to a Weber 32/36 DGAV, which is a bolt-on replacement that provides better throttle response and easier tuning. Budget $300-500 for a Weber conversion.