A dark green Bentley 4½ Litre Blower, front three-quarter view on a british-green field with an amber band

Market value · road

$3.5M–$7M

Typical $5M · 1 sales

$481K$7.4M

Open Market & Price

4½ Litre "Blower"

Supercharged against W.O.'s judgement

Tim Birkin and Amherst Villiers put a Roots supercharger ahead of the radiator, nearly doubling the 4½ Litre's road output. Original road cars, team cars, later conversions and modern Continuations require separate pricing.

View details

Market value · road

$3.5M–$7M

Typical $5M · 1 sales

$481K$7.4M

Open Market & Price

Market value · road

$3.5M–$7M

Typical $5M · 1 sales

$481K$7.4M

Market history builds with the record

Open Market & Price

Engine

4'398 cc four

SOHC · supercharged

Road power

175 bhp

factory Heritage figure

Team power

240 bhp

4'200 rpm · race tune

Road top speed

97.8 mph

Bentley demonstrator figure

Team top speed

125 mph

racing trim

Production

period accounting varies by one

Engine

4'398 cc four

SOHC · supercharged

Road power

175 bhp

factory Heritage figure

Team power

240 bhp

4'200 rpm · race tune

Road top speed

97.8 mph

Bentley demonstrator figure

Team top speed

125 mph

racing trim

Production

period accounting varies by one

Market & Price

The price and the proof

A terminal for one car: the model curve over the documented record, the benchmarks it is measured against, and the instruments that read it.

HCN:4LITREBLLive model

$5'000'000107.4% · 12M

Model curve · anchored to 2 documented sales · benchmarks rebased at window startmodel v1 · seed bentley-41-2-litre-blower · not investment advice

The readouts · model figures against the benchmarks2 documented anchors · last sale this month

Compound annual growth

Window	This car*	S&P 500	Gold
1Y	+107.4%	+18.8%	+21.9%
5Y	+86.7%	+11.4%	+17.6%

*Modeled price CAGR · S&P is a price index, no dividends

Deepest drawdown · model window

This car*-0.6%Feb 2020 → Mar 2020 · recovered Apr 2020

S&P 500-20.3%Dec 2021 → Oct 2022 · recovered Dec 2023

Gold-18.9%Feb 2026 → Jul 2026 · not recovered

Forecast ladder · model quantiles

Horizon	P10	P50	P90
+6M	$4.8M	$5.2M	$5.7M
+12M	$4.9M	$5.4M	$6.0M
+24M	$5.1M	$5.9M	$6.8M

Median path with the 10th and 90th percentile · not investment advice

Transaction ledger · documented salesMixed price basis · not estimates

2 of 2 recorded sales · shown in USD · recorded currency in each record

Original road cars and Birkin team cars are separate markets; later conversions are not Blower comparables.

Price range · road · openConfidence · lowThe two strongest documented USD sales are from 2007 and 2015, while a third result shows the discount for a production car rebuilt in team style. Public trades are too sparse and old for a tighter current band.

Floor

$3.5M

Typical

$5M

Ceiling

$7M

Estimate band for good road cars. 1 documented sales since 2019 plotted below.

$471K$3.5M$5M$7M$7.6M

Hover the spectrum to read a value, or a dot for the sale behind it.

Band and axis shown in USD. Sale positions use indicative fixed-rate conversion to USD; sale readouts retain recorded currencies. USD; original factory-supercharged road cars with documented identity. Team cars sit outside the band.

The wider market · Bentley at auction · median per year · modeled between anchors1,032 lots · 2003–2026 · exact yearly anchors · modeled line

Explore all 40,882 results

Instrument calibration for this file is in progress — the terminal above reads the documented record directly.

Published sold totals are recorded without currency conversion. An unsold 2022 high bid and continuation cars are excluded from the ledger.

Overview

Birkin chose pressure where W.O. Bentley chose capacity.

W.O. Bentley opposed supercharging the 4½ Litre. Tim Birkin pursued it with independent engineer Amherst Villiers, secured chairman Woolf Barnato's approval and found the racing budget through Dorothy Paget.

Fifty road cars were required for homologation. Birkin & Co. developed four team cars at Welwyn Garden City; production chassis and engines came through Bentley, while the team cars carried stronger parts and up to 240 bhp in race tune.

The Blower set pace and lap records but did not deliver a period endurance victory. Its market identity rests instead on the small production run, the external supercharger and the surviving documentary boundary between factory-supercharged cars and later conversions.

Built: 55 period cars
Road cars: 50 homologation
Team cars: 4 Birkin cars
Supercharger: Amherst Villiers Mk IV
Endurance wins: None in period

Reference

Technical specifications

Powertrain

Engine: 4'398 cc inline-four100 mm bore, 140 mm stroke; fixed cast-iron head
Valvetrain: Single overhead camshaft, 16 valvestwin ignition
Supercharger: Amherst Villiers Mk IV Roots typecrankshaft-driven and mounted ahead of the radiator
Road output: 175 bhp at 3'500 rpmBentley factory Heritage Collection figure
Team output: 240 bhp at 4'200 rpmfactory figure for Team Car No. 2
Transmission: 4-speed manualclose-ratio D-type on team specification

Chassis

Frame: Pressed-steel ladder chassisteam cars used the 117.5 in wheelbase; production tourers commonly 130 in
Suspension: Solid axles and semi-elliptic leaf springs
Brakes: Bentley-Perrot mechanical drums15.75 in on Bentley's team-car specification
Road performance: 97.8 mph · 0 to 60 mph in 15 sfactory figures for demonstrator GH 6951
Team performance: 125 mphfactory figure for UU 5872 in racing trim

The records

period Blowers

Bentley's published headline

0bhp

team-car output

period endurance wins

HICON BID

Buying interest, silently.

A HICON Bid is a confidential expression of buying interest on the Bentley 4½ Litre "Blower" file — never public, never shown to other members. It is not a binding purchase, and HICONIUM holds no funds.

HICON Bids are a member instrument. Sign in to place one.

The vault

Open a file on yours.

You keep one? The record starts in your garage — identity, papers, photography, and the market evidence this file already carries, bound to your chassis.

The variants

One badge, 3 executions

The register separates the 4½ Litre "Blower" into its documented executions. One reference silhouette per execution — each opens as its own file as the archive fills.