Hartwell Imp
Summer 1964, Hartwell group 4 Imp GRH 5, 998cc.

The Imp Site

George Hartwell Ltd.

There were early connections between George Hartwell and Lord Rootes: the Hartwell Coupes. [Hartwell history]

Hartwell did not only build racers, they made all manner of gear for road going cars. They were Rootes specialists and they had raced Imps for a long time.
Though Hartwell were known to be a tuning specialist (see 1965 advert), who would do a lot for any Imp offered them, they did sell some Imps off the showroom floor.

Hartwell Imp GT
Hartwell Clubman
Hartwell advertisement
Hartwell Group III
Hartwell Tuning, a George Hartwell Ltd. enterprise

You could take your Imp to Hartwell and they would bring the engine up to full Hartwell 1000 specification (1970: for upwards of £195). They could supply any new Imp variant to the specification you required and would give you a quote. Whether you were shopping for some engine gear or a complete car, Team Hartwell could deliver.

Team Hartwell manager Barry Green

Motor, 1965, week ending October 1965, p.73:

George Hartwell has been made a Fellow of the Institute of Marketing. He is managing director of Rootes Ltd., and chairman of the Robins and Day Group.
  The Hartwell Imp - Hartwell Tuning
Hartwell Tuning, a George Hartwell Ltd. enterprise
(click to enlarge) - Febr. 1966
    advert 1971 Oct. CCC
Team Hartwell, a division of George Hartwell Ltd.
October 1971 - 1972
  Hartwell advert April 1975
April 1975
  CCC April 1976, 3 wheels, 4 wheels or boat
April 1976

Hartwell Imp GT

A Hartwell engineered Imp is a sensible choice for the Impman who wants power and flexible running. In June 1969 Hartwell ltd. came to this conclusion and decided to market a Hartwell GT. It's based on the Imp Sport.

An extremely quick and practical Imp, based on the Sunbeam Imp Sport with twin Stromberg carburettors and sport camshafts as standard. If all the extras were fitted, it may have been called Arrow (I'm not sure).

The Hartwell Treatment:

Boring the Mk2 875 block out to 998cc
   with half wet liners
Checking bottom end components for balance
   (though normal Rootes components were fairly accurate)
Using flowed inlet ports
   and larger 1.325 " dia valves
   specially lightened and flowed, like the exhaust valves
Hartwell's normal Imps suspension kit
   consisting of shorter, stiffer springs all round
   which lowers the car 1¼"
   and sets all wheels to 2° negative camber
155 SP 68s on 5½" rims

Front and rear panels are painted matt black
Front bumper is cut up to leave only a pair of quarters on each side


It is slightly quicker in top speed than a Sunbeam Stiletto, with a maximum of just on 94mph. And it is usefully quicker through the gears.
  Hartwell GT    Sunbeam Stiletto  
  0 - 60mph  13.716.1 secs
Because of the extra capacity it pulls better in top gear, from as low as 20 mph. Constant speed fuel consumption figures indicate that the extra efficiency of the head work shows up almost throughout the rev range as the 1 litre is more economical from 40mph upwards. (However, the extra performance inspired non-economical driving.)

10,000 rpm rev counter£20
leather-rimmed steering wheel8 gn.
oil pressure gauge (vaguely calibrated)£7
Hartwell cylinder head
  gas flowed with reshaped chambers
  compression is raised to 9.6:1
  and the standard sizes valves are polished  
£32 10s
twin 40 DCOE Wbers
  with fabricated combined inlet and exhaust manifold
  and special air box
blocks between the axle and the springs
  to lower the rear 1½"

Hartwell Clubman

A converted Hillman Imp. The change concerned the engine, the suspension and the gears. Various parts were available as separate kits.

The block was bored out to give 998cc and fitted with special pistons, a balanced crankshaft and a lightened flywheel. It had Hartwell's Mark 2 engine, which has larger valves.
inlets: 1 5/16" (=0.3125 - other source says 1.35" [Sports use 1.28"])
exhausts: 1 1/16"

It had gas flowed inlet/exhaust ports and valve throats and balanced combustion chambers. The head is machined and a tube inserted to facilitate oil drainage back to the crankcase. An R17 is used, together with a multi-holed sprocket and matching distributor. A Weber 40 DCOE carburettor, modified inlet and exhaust manifolds, pancake air cleaner and Burgess silencer. And an oil cooler.

Once upon a time The Imp Club had a separate register for the Clubmans. In 1982 Ron Gregory was Model Register for Hartwell Clubmans.


an advert in Autocar, 26 November 1965

Hartwell advert

Stages 1,2 and 3 available on 875 c.c.
Group 4 available on 998 c.c.

With its modified brakes and suspension, twin Strombergs, high cp,pression head, special camshaft, four branch manifold and high efficiency tuned length exhaust system, it is an established winner in local and national events.
The exhilarating performance and superb road-holding make it a favourite with the Sportsman, Businessman and Pleasure Motorist.
Let Hartwell tune your Imp now and enjoy the thrill of fast and safe motoring throughout the year.
Write for details, prices and current Road Test Reports to: -


At Hartwell's autum 1970
At Hartwell's, autumn 1970 - CCC visiting, reviewing Hartwell Imp mods

  standard Imp Hartwell
Hillman Imp

(Group 2)
Hillman Imp

(Group 3)
Hillman Imp

(Group 4)
Hartwell GT Imp Sport
Engine As standard 875cc Imp, except for reshaped and polished valve throats, ports, cylinder head chambers and manifolds; stronger valve springs; raised compression ratio; tuned-length four-branch exhaust system   998cc 998cc  
Transmission  As standard Imp   Hartwell
Hillman Imp

(Group 4)
Suspension As standard Imp, except for slight lowering of front end to reduce front-wheel camber   lowered and stiffened suspension with limited travel; Koni dampers   
Brakes  As standard Imp   brake servoa sn competition liners for the drums   
Dimensions  As standard Imp   spacers to increase the track   
Weight        glassfibre boot-lid and eingine cover; perspex side and rear windows; no heater; Mini-Lites
Maximum speed
Mean of 2 ways
94.7mph. @ 6,800rpm
Speeds in gears
  27mph / 44kph
50mph / 80kph
72mph / 116kph
    0 - 30
    0 - 40
    0 - 50
    0 - 60
    0 - 70
    0 - 80
    0 - 90
  5.3 sec.
  8.6 sec.
14.7 sec.
23.7 sec.
37.0 sec.
  4.9 sec.
  7.7 sec.
11.0 sec.
16.0 sec.
24.9 sec.
  4.1 sec.
  6.9 sec.
  9.6 sec.
14.2 sec.
19.4 sec.
27.7 sec.
  3.5 sec.
  5.8 sec.
  7.8 sec.
11.1 sec.
15.3 sec.
22.2 sec.
36.5 sec.
13.7 sec.
16.1 sec.
Standing ¼ mile 21.9 sec.   19.0 sec.      
 standard ImpHartwell Hillman Imp (Group 2) Hartwell Hillman Imp (Group 3) Hartwell
Hillman Imp

(Group 4)
Hartwell GT Imp Sport


Group III engine conversion

Black & yellow CLJ 195C in 1965

The head can be supplied on an exchange basis. For £56 10s:

Costing £53 10s:

The test car also had:

At a road average of 40mph, fuel consumption rose by only 3mpg.
At an average of 60mph, there was an extra of 5mpg.
It did not use any oil that could be noticed.
Hot or cold, it always started the first time.



   advert 1967 June CCC
June 1967
850 Imp outright winner
CCC, January 1968

Hartwell's Hot H'Imp, Motor 1964, August 22
Testing GRH 5. 1 page
reproduced in Impressions 1999, November. - p.31

Go-faster specialists, Hartwells of Bournemouth. - Motor 1965, January 27. - p.13,15
Part of Rootes Owners' Supplement

Nathan-tuned and Hartwell Stage III Hillman Imps: improving the performance of popular cars. - Autocar 1965, 30 April, p.872 - 874
Roger Nathan (racing driver + tuning expert) offered several tuning packages and Autocar tested one, BLC 808B. It had a 998 and could top 107mph. 0-60 in 12 secs. Brakes were unchanged, suspension too (well, it was slightly lowered). The testers were impressed but hesitant where the car's high speed behaviour was concerned.
reprint in Impressions 1987, June.

Hartwell tuned Imp : Practical Motorist perfomance car test. - Practical Motorist 1965, August
Testing CLJ 195C, a Group III engine conversion
Reprinted in Transport Source Books 081. - p.24

Hartwell Imp Group III : modified car series no. 6. - (Sporting Motorist 1965 ?)
reprint in Unique Master Portfolio. - p.62-63

Hartwell: group two Imp : converted car test. - (Car Illustrated 1967 ??). - p.204-205
JYP 911D. Property of mr. R.A. Wimbush, Rootes Group's marketing manager.
reprint in Impressions 1985, Dec.
reprint in Unique Master Portfolio. - p.60-61

Hartwell Group 4 Imp : 998 cc : improved performance test. - Autocar 1965, November 26. - p.1142-1143
Reprinted in Impressions 4 (1984), 2/3 (Feb./March)

Some converted Imps we have tried. - (Car and Car Conversions 1966)
Emery stage 1; Hartwell stage 3 (CLJ 195C) ; Nathan's Impudence II (317 XOV)
Reprinted in Unique Master Portfolio, p.64-65 (quoted as from 1968)

H is for Hartwell: the tuners. - Car and Car Conversions 1966
Reprinted in Unique Master Portfolio, p.58-59 (quoted as from 1967)

Imp & Chamois Supplement. - Cars and Car Conversions 1966, September. - 30 p.
p.204 - Hartwell Stage II Imp
p.211 - The Tuners - Hartwell

Californian here we come : standard and Hartwell modified versions of Rootes' low-line Imp. - Car 1967 ??
reprint in Unique Master Portfolio. - p.24-25

Those high-speed Imps: trying the Hartwell Stiletto and Ginetta G15. - Autocar 1969, March 13. - p.2-4
Comparison between Hartwell Sunbeam Stiletto, Ginetta G15, Sunbeam Imp Sport & Hillman Imp. 3 pages

Group test no. 13: tuned cars : Motor's test team go driving in convoy to try competitive cars under identical conditions. - Motor 1969, May 31. - p.43-48
LuMo Pirana; Hartwell Stiletto (GRH 5); Master Hunter; Downtown 1300 (BMC); SAH 1300 (Triumph); Blydenstein Viva
Reprinted in Transport Source Book 187. - p.58-63

This Stiletto's no heel. - Cars and Car Conversions 1969, July. - p. 669-670
Hartwell Stiletto road test

Hartwell's big Sport 1-litre Imp. - Hot Car 1970, April. - p.50-52
Test of Hartwell Imp GT (based on Sunbeam Imp Sport Mk III). 3 pages

Motoring plus / by Jim Tosen. - Motor 1970, May 16. - p.58
The Hartwell 1-litre GT.
Reprinted in Impressions Apr./May 1986

Team Hartwell Imp mods / Clive Richardson. - Car and Car Conversions 1970, December. - p.433. - [CR calls the tune]
The first of a new series on the specialist car builders and tuning firms by Clive Richardson, formerly Sports Editor of the BL magazine, High Road.

Improving performance. - Car Mechanics 1971, March. - p.75-77. - [Hot Shop]
"we comported ourselves to the doorstep of one Barry Green, of Team Hartwell in Bournemouth - and found one of the most efficient tuning shops it has been our pleasure to disrupt for a day."

Hogged out Imp : power economy by Hartwell / CR. - Cars & Car conversions 1971, July. - p.781
Reprinted in Impressions Oct 1986
Reprinted in Transport Source Book 187. - p.72

Invigorating Imp / AA. - Custom Car 1971, October. - p.58
(Hartwell Imp)

Hot ones from Hartwell: Clubman Imp / Rex Greenslade. - Motor 1973, 13th October. - p.42-43
testing BRU 200L
Reprint in Transport Source Book 187, p.80-81

Hartwell Clubman. - Hot Car 1973

Hartwell's thrifty shifter. - Hot Car 1975, March. - p.53
38mpg, driven hard!

The Imp (no. 2): our backpages. - Cars & Car Conversions 1989 May, p.117-120
Interviewing Ray Payne of Team Hartwell on what can be done to improve the Imp.

A racing heritage / David Lillywhite. - Practical Classics 1994 November. - p.64-68
Specialist tuning houses. Four originally-converted cats, one (p.67) the racing Imp, built and raced by Ray Payne.

6 September 1964 - Nürburgring (D): Round 7, International Championship for Manufacturers
R.W. Wickson and Alan Hartwell drove a Hillman Imp (entered by R.W. Wickson, car# 54, class: Touring 1000), but they did not arrive.

The Imp Site
   The Imp family
   Imps in competition
      Racing Imps
         Ray Payne
      Rallying Imps
         Andrew Marsden: Most commonly bought conversion offered by Hartwell
   Imp Tuners & Builders
      George Hartwell Ltd.
               Hartwell Ltd and Rootes Motors in 1968
               Advice from the Hartwell workshop - visiting the Team Hartwell tuning shop in Bournemouth
               Team Hartwell price list, 1992
               Hartwell Tuning folder - 53.2 x 20.3mm, once folded makes 4 pages of 26.6 x 20.3cm
               Team Hartwell folder (Ray Payne - chief engineer), folded thrice makes 8 pages of 10 x 17.8cm
(There was another folder, nearly the same, but in stead of Ray's name up front: Geoff Kilbey - Team Manager)
               Hartwell letter heads 1968; 1992
© Franka

George Hartwell Ltd. (Peugeot) George Hartwell, Peugeot dealer at Bournemouth
3 Oxford Road