Servicing Your AC Aceca-Bristol
A basic service is within reach of a careful home mechanic. The Bristol six is a well-engineered, durable unit, it will happily cover 100,000 miles, but it has its own quirks: small 10mm spark plugs, triple Solex carburettors, and a Vokes (or converted spin-on) oil filter. The ash-framed alloy body also wants its own care.
Which engine do you have?
This section began as a guide to the Bristol engined car and is being extended to cover AC's own engine. They are entirely different units and almost nothing transfers between them, so start by establishing which you have. A chassis number beginning AE means the AC Light Six. BE means the Bristol 100D2. RS means the Ruddspeed Ford 2.6. The chassis guide explains the prefixes in full.
Pages written for the Bristol engine are the oil and filter, cooling, valve clearance and spark plug pages listed below. The AC Light Six now has its own set of four covering the same ground, and each Bristol page links across to its AC equivalent.
- Cooling the AC Light SixCoolant choice on a mixed metal engine, and the water pump's design fault.
- AC Light Six engine oil & filterMonograde SAE 30, low hot idle pressure and the bypass filter.
- AC Light Six valve clearances0.020in hot, the roller rockers and what the job tells you about wear.
- AC Light Six plugs & ignition14mm plugs, contact breaker gaps and a timing figure in dispute.
Which car this covers
This section covers the Bristol-engined Aceca (chassis prefix BE). The AC-engined (AE) and Ford-engined (RS) cars differ. Exact capacities, grades, plug specifications and settings for the Bristol engine and gearbox are specialist knowledge. Always confirm them against the official Bristol/AC Workshop Manual and the AC Owners Club and Bristol Owners Club. Where a figure is not stated here, that is deliberate: the clubs and your handbook are the authority.
Service intervals
Indicative, the handbook is the reference.
- Weekly / before a run: check engine oil and coolant (cold) and tyres.
- Every few thousand miles / annually: engine oil & filter; check/clean the spark plugs; check/top up gearbox and rear-axle oil; balance the triple Solex carburettors; check the ignition timing.
- Periodically: renew the coolant; renew the brake fluid; renew the gearbox and rear-axle oils.
- Ongoing: keep on top of alloy-body/chassis corrosion care.
Tools & consumables
- Trolley jack and axle stands, wheel chocks, drain pans
- The correct spanners, thin 10mm spark-plug socket
- Feeler gauges, torque wrench
- 20W/50 oil; oil filter (Vokes element or spin-on)
- 10mm spark plugs (six)
- Gearbox and axle oil to the correct grade
- Coolant, brake fluid, new washers
Safety
- Support the car on axle stands on firm level ground and chock the wheels.
- Drain oil warm, not scalding.
- Antifreeze is toxic and sweet-tasting, lethal to pets and wildlife.
- Used oil, filters and coolant are hazardous waste, take them to a recycling centre, never down a drain.
- Many 1950s British cars are POSITIVE earth. Check your car's polarity and disconnect the battery before electrical work.
The tasks
Engine oil & filter
20W/50, the Vokes vs spin-on filter, and the oil-cooler catch.
Open the guideSpark plugs
The 10mm plug question, and why owners run motorcycle plugs.
Open the guideCooling the Bristol six
Coolant, radiator, water pump, thermostat and reading the gauge.
Open the guideValve clearances
The cross-pushrod valve gear explained, and how to approach setting it.
Open the guideOils & fluids
What goes where, engine, gearbox, diff, clutch, brakes and coolant.
Open the guideSuspension & chassis grease
Which grease for the nipples, obsolete originals and the modern NLGI 2 equivalent.
Open the guide
Also part of a full service
- Cooling-system careCoolant renewal, hoses and header tank.
- Brake-fluid serviceBleed and renew hydraulic fluid.
- Balancing the triple Solex carburettorsAir-balance and mixture on three carbs.
- Solex carburettor referenceThe 32 BI in detail.
- Ignition timingStatic and stroboscopic setup.
- Alloy-body corrosion careGalvanic corrosion and ash-frame damp.
- Fuel, oil & additivesModern pumps, ethanol and ZDDP.
- The Bristol engineBackground to the cross-pushrod six.
Confirm before you drain anything
Gearbox & rear-axle oils: the Bristol four-speed gearbox (with its freewheel first gear, and the optional A-type overdrive) and the AC hypoid rear axle take specific grades and quantities. Confirm these against your workshop manual and the AC/Bristol Owners Clubs before draining anything.
Air filter: the air-cleaner arrangement on triple-Solex Bristol engines varies from car to car. Check the type fitted to yours before servicing it (see carburettor care).
This guide is not a substitute for the official Bristol/AC Workshop Manual.
About the author
A lifelong classic-car enthusiast in North Yorkshire, near Thornton-le-Dale, who owns and maintains an AC Aceca, writing the single-model reference he always wished existed. Read the full bio.