AC Bristol

Not a model name at all, a shorthand for every AC built around Bristol's two-litre six.

Search for an "AC Bristol" and you will find three different cars, all of them correct. AC Cars never sold a model called the AC Bristol: the term is enthusiast and auction-house shorthand for a Thames Ditton-built AC fitted with the 1,971 cc Bristol straight-six in place of AC's own engine. Between 1956 and 1963 that engine went into the Ace roadster, the Aceca coupé and the four-seat Greyhound, and each gained the Bristol suffix.

The distinction matters when you are buying, valuing or researching a car, because the three share a drivetrain and almost nothing else in price. This page explains what the term covers, points you at the detailed record for each model, and links to the engine itself.

The three Bristol-engined ACs

Why AC used a Bristol engine at all

AC's own six, the Weller-designed, wet-linered overhead-cam unit, was already three decades old when the Ace appeared in 1953, and it was being asked for power it was never designed to make. Ken Rudd's privately fitted Bristol engine demonstrated the answer before the factory adopted it: Bristol's 100D2 was lighter in feel, far more willing to rev, fed by triple Solex downdraught carburettors and backed by a Bristol four-speed gearbox with a freewheel on first. In Ace form it turned a pretty sports car into a class winner.

Bristol ceased engine supply in 1961 as it moved to Chrysler V8s for its own cars, and AC turned to a tuned Ford Zephyr 2.6, producing the Aceca 2.6 and the last Greyhounds. By then Carroll Shelby's V8 proposal was already on the drawing board, and the Bristol era at Thames Ditton was effectively over.

Telling a Bristol car from an AC-engined one

The quickest guide is the chassis number. Aceca prefixes run AE for AC-engined cars, BE for Bristol-engined cars and BEX for left-hand-drive Bristol export cars; the equivalent Ace prefixes follow the same logic. Under the bonnet, the Bristol car carries three sidedraught-mounted Solex instruments on a tall inlet manifold and a distinctly different rocker arrangement, because the exhaust valves are operated by long cross-pushrods running over the head. The chassis and numbering guide sets out the full prefix system, and the authenticity guide covers what to check when a car's engine and chassis no longer agree.

What they are worth

A Bristol engine adds a substantial premium to any of the three models, and the body style then decides the rest: an Ace-Bristol typically trades well into six figures, an Aceca-Bristol below it, and a Greyhound below that again despite being the rarest of the three. Recorded auction results and current price bands are set out on the Aceca prices page and, for the roadster, the AC Ace values page.