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MOTRS

MGA

1955-1962 / Roadster / Coupe / United Kingdom

All MGA problems All workshop issues
Common Engine, BMC B-Series (1,489cc / 1,588cc)

Carburettor Wear (SU H4)

Symptoms

Rough idle, poor fuel economy, hesitation on acceleration, black smoke from the exhaust. The engine may run rich or lean depending on which component has worn.

Cause

The SU H4 carburettors use a throttle shaft that rotates in the carburettor body. Over decades, the shaft wears the bore oval, allowing unmetered air to enter. The jet and needle also wear, affecting mixture control. The dashpot piston and suction chamber can wear, affecting the carburettor's response to throttle changes.

Fix

Rebuild the carburettors with new jets, needles, gaskets, and throttle shaft bushes.

Throttle shaft rebushing requires removing the carbs and having the work done by a specialist, the bodies need reaming and new bushes pressing in.

Cost: $80-$150 per carb for basic rebuild kits; $150-$300 per carb for complete rebuild including shaft rebushing.

Cost mentioned in fix
Cost: $80-$150 per carb$150-$300 per carb

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// More MGA problems

Other known issues

Critical Engine, BMC B-Series (1,489cc / 1,588cc)

Oil Leaks

Oil weeps from the rocker cover gasket, timing cover, rear main seal, and sump gasket. A layer of oil covers the engine and transmission.
Critical Engine, BMC B-Series (1,489cc / 1,588cc)

Head Gasket Failure

Coolant loss without visible external leak. White smoke from the exhaust. Milky emulsion under the oil filler cap. Overheating. Bubbles in the header tank.
Common Engine, BMC B-Series (1,489cc / 1,588cc)

Timing Chain Stretch

A rattling noise from the front of the engine at idle. Valve timing wanders, reducing power and efficiency.
Minor Rust

Sill (Rocker Panel) Corrosion

The sills become soft, bubbly, or perforated. The body may flex excessively when jacked up or driven over bumps. Doors may not shut properly as the body distorts.
Common Rust

Floor Pan Corrosion

Soft or perforated metal in the floor pans, visible from underneath. Water may pool in the footwells. The floor may flex under foot pressure.
Minor Rust

Front Crossmember Corrosion

Visible rust, scaling, or perforation of the front crossmember (visible from underneath the front of the car).
View all 16 MGA problems