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MOTRS

MGA

1955-1962 / Roadster / Coupe / United Kingdom

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Minor Engine, Twin Cam (DOHC 1,588cc)

Piston and Bore Damage

Symptoms

High oil consumption, blue smoke from the exhaust, loss of compression. In severe cases, complete piston failure.

Cause

The Twin Cam engine's high compression ratio (9.9:1) and tendency to pre-ignite on poor-quality fuel causes piston crown erosion and bore scoring. Early engines were particularly prone, the combination of high compression, inadequate fuel quality, and owner ignorance about fuel octane requirements destroyed many engines.

Fix

Rebore and fit new pistons (lower compression pistons are available for improved reliability).

A complete Twin Cam engine rebuild is a specialist job.

Cost: $5,000-$10,000.

Cost mentioned in fix
Cost: $5,000-$10,000

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Other known issues

Minor Engine, Twin Cam (DOHC 1,588cc)

Oil Consumption

The Twin Cam consumes oil at a rate that seems alarming to anyone accustomed to modern engines. Topping up between services is normal.
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).
Minor Rust

Rear Spring Hanger Corrosion

The rear spring mounting points show rust, cracking, or distortion. The rear of the car may sit unevenly or make clunking noises.
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.
View all 16 MGA problems