Car Collector International
Classic · 1929–1931

Bentley 4½ Litre Blower

Tim Birkin's supercharged 4½ Litre — the most famous Bentley of the vintage era and a Le Mans icon despite never winning outright.

Car Collector International Editorial
British Racing Green Bentley 4½ Litre Blower tourer in a bright studio, front three-quarter view showing the polished radiator shell, mesh stone-guard grille, Amherst Villiers supercharger mounted ahead of the radiator, twin fabric-strapped headlamps, Union Jack livery on the bonnet side and wire-spoke wheels with knock-off centres.
OverviewVariants & SpecsCollector VariantsBuyer's GuideOwnershipCommon ProblemsAuction ResultsInvestment OutlookRecommended Network
Overview

Why this car matters

Built against W.O. Bentley's own preference for naturally aspirated engines, the Blower Bentley was conceived by Sir Henry 'Tim' Birkin and financed by the Hon. Dorothy Paget. A Roots-type Amherst Villiers supercharger was fitted ahead of the radiator, raising the 4,398cc four-cylinder's output to around 175 bhp in road trim and over 240 bhp in racing form. Only 55 Blowers were built (50 production cars plus five works racers) to satisfy Le Mans homologation requirements. None ever won at Le Mans, but Birkin's harrying of the Mercedes SSK in 1930 — using up the German car so the works Speed Six could win — created the Blower legend.

The most charismatic of all vintage Bentleys; supercharged engineering, period race history and tiny production numbers combine for permanent collector status.

Variants

Range and production

VariantYearsProductionNotes
Blower 4½ Litre (production)1929–193150Customer cars built to satisfy homologation; varied coachwork.
Birkin Team Cars1929–19305Works racing cars; the most valuable of all Blowers.
Collector Variants

Limited & special editions

The models below represent the most significant limited and special edition variants — factory-produced cars that command meaningful premiums over standard examples and warrant specific attention from serious collectors.

4½ Litre 'Blower Bentley' (Birkin Team Cars) · 1930

55 Blower Bentleys were built in total. Of these, 5 were the Birkin Team Cars prepared specifically for racing — these are a distinct sub-group within the 55-car production run, not additional to it.
Distinguishing features
Sir Henry 'Tim' Birkin's supercharged 4½ Litre, built independently of W.O. Bentley's wishes. 175–240 hp depending on tune, Villiers/Amherst supercharger projecting forward of the radiator.
Value premium
Multi-million dollar; the 5 Birkin Team cars are standalone tens-of-millions.
Inspection points
Bentley Drivers Club Heritage register and W.O. Bentley records are essential.
Authentication
Many 'Blower-style' rebuilds exist on 3 Litre or unsupercharged 4½ Litre chassis. Only Bentley factory-built Blowers (chassis numbers in the published register) are originals.
Buyer's Guide

What to look for

Provenance and originality

For pre-war and vintage cars such as the Bentley 4½ Litre Blower, provenance is paramount. Chassis and engine number matching, period coachbuilder records, factory build sheets where available, continuous ownership documentation, original handbooks and any competition or concours history are the foundation of value. Original supercharger and matching numbers, Vanden Plas team-car style coachwork, verified period race history.

Mechanical inspection priorities

The Villiers blower is the defining feature and the most expensive component to maintain. Confirm rebuild history, drive coupling condition and oil-feed integrity; the supercharger raises stress on bearings and head gasket throughout. A pre-purchase inspection by a recognised marque specialist should include compression and leak-down testing, magneto and ignition checks, chassis straightness and frame survey, axle and steering wear assessment, brake system review (mechanical or hydraulic per period), and an extended road test on varied terrain to expose carburation, cooling and gearbox issues that only emerge under sustained running.

Body, chassis and originality of coachwork

Pre-war coachwork is rarely truly original after a century of use. Establish whether the body is original to the chassis (period photographs, build records, coachbuilder plates), whether it has been re-bodied at any point, and the standard of any restoration. Quality of timber framing, ash health, panel beating and paint depth are all critical. Concealed structural rot, re-bodies presented as original, and 'tribute' cars built on later or unrelated chassis must be priced accordingly.

Specification and event eligibility

Verified one of the 55 original supercharged cars with documented period coachwork — not a later W.O.-built 4½ Litre converted to supercharged specification. Birkin works-team provenance is the highest tier. For vintage cars, event eligibility — Mille Miglia, Goodwood Revival, Pebble Beach, VSCC events, Le Mans Classic — can underwrite a substantial proportion of market value. Verify FIA/FIVA papers, period race history where claimed, and the car's standing with the relevant marque registry before purchase.

Ownership

Living with it

Typical mileage
300–2,000 miles typical for vintage use; rally cars higher
Service interval
Annual full service; pre-event check before any rally or tour
Annual running cost
$8,000 – $35,000 depending on use, storage and event programme
Fuel economy
10–18 mpg typical; heavy carburetted engines run rich
Insurance
Use a specialist agreed-value vintage policy with declared value reviewed annually. Premiums reflect declared value, storage, event use and driver experience with pre-war machinery.

Maintenance planning

Vintage cars require disciplined preventive maintenance: lubrication regimes, magneto service, carburettor synchronisation, brake adjustment, and timber and trim conservation. A car used regularly and serviced annually by a specialist will outlast a stored example neglected for decades.

Specialist access and parts

A small number of UK and European specialists handle Blower-specific work; supercharger overhaul is a specialist sub-discipline. Confirm the availability of marque specialists, period-correct fasteners, coachwork trim, instruments and tyres before committing. A car requiring fabricated one-off parts will absorb time and cost that a similar example with active specialist support will not.
Common Problems

Known issues by system

Supercharger

Roots-type Amherst Villiers blower bearing and rotor wear

Major$20,000 – $50,000 (blower rebuild)
Symptoms — Whine becoming rumble, loss of boost, oil mist at carburettor.
Inspection — Boost pressure test; remove blower for rotor clearance and bearing inspection.
Engine

Detonation damage to pistons from incorrect fuel / over-boost

Critical$30,000 – $70,000 (engine rebuild)
Symptoms — Holed piston, heavy blow-by, dropped compression on one cylinder.
Inspection — Compression and leak-down on all four; borescope inspection; check ignition timing on octane in use.
Cooling

Boiling at idle / inadequate radiator for blown engine

Moderate$5,000 – $12,000
Symptoms — Coolant loss in traffic, sustained running over 95°C.
Inspection — Pressure-test radiator and header; verify correct high-capacity 'Blower-spec' core is fitted.
Identity

'Blower' built up from unblown 4½ chassis

CriticalValue impact: factory vs. tribute differential exceeds £3m
Symptoms — Period photographs and works records do not list car as factory Blower; engine number outside Blower range.
Inspection — Cross-reference with Bentley Drivers Club Blower register; only 55 factory cars exist.
Auctions

Recent results

DateAuctionCarMileageResult
2024-02-21
RM Sotheby's
British Classics
1928 4½ Litre Supercharged Le Mans Tourer
—
€356,500
Sold
2023-11-04
RM Sotheby's
London (Lot 220)
1929 4½ Litre Supercharged Le Mans Tourer
—
£815,000
Sold
Investment

Long-term outlook

Blue ChipHorizon: 10+ years

Iconic, finite production, irreplaceable history. Original Blowers remain at the very top of the pre-war market.

Our view, not advice. This section is Car Collector International's editorial judgement on where this model sits in the collector market, based on the production, specification and market data set out in this guide. It is not a recommendation to buy or sell and it is not investment advice. Values can fall as well as rise.

Recommended

The trusted network

Specialists

  • Bentley marque specialist
    View →
    UK / Europe
    Bentley 4½ Litre Blower restoration, mechanical service and originality reviews.
  • Pre-war coachwork specialist
    View →
    International
    Timber framing, ash conservation, panel beating and period-correct paint for pre-war coachwork.
  • Concours preparation studio
    View →
    International
    Concours preparation, detailing and event support for pre-war and vintage cars.
  • Hagerty
    View →
    USA / UK / EU
    Agreed-value collector insurance specialising in pre-war and vintage cars.
  • Lockton Performance
    View →
    UK / EU
    Specialist agreed-value cover for significant pre-war and competition cars.

Storage

  • Windrush Car Storage
    View →
    London & Cotswolds, UK
    Climate-controlled storage and collection management for pre-war and classic cars.
  • AutoVault
    View →
    Essex, UK
    Dehumidified storage at 55% RH in purpose-built sealed buildings, with maintenance programmes and individual motor-trade insurance cover.
  • Classic Car Club Manhattan
    View →
    New York, NY
    Secure urban storage for collector and pre-war cars.

Transport

  • CARS UK
    View →
    UK & Europe
    Enclosed concours and event transport for pre-war and vintage machinery.
  • Reliable Carriers
    View →
    USA (national)
    Enclosed coast-to-coast transport for pre-war American and European cars.
  • FERRLOG
    View →
    Italy / Europe
    Air-ride enclosed transport for Italian and European collector cars.
Related

Continue researching

Enjoyed this guide?

Get new buyer's guides and collector market intelligence delivered to your inbox. No spam. We respect your inbox.

The valuation figures in this guide are for research purposes only and do not constitute financial or investment advice. See our full disclaimer.