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

The Imp Site

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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.

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

Team Hartwell, a division of George Hartwell Ltd. October 1971 - 1972

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

Performance

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	13.7	16.1 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.)

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.

Most commonly bought conversion offered by Hartwell

Andrew Marsden
June 7, 2010

I can add a little to your write-up on Hartwell Imps. In September 1971 I purchased a 'showroom model' Imp from Team Hartwell. It was based on the cheapest model (without frills eg no heater blower, cerulean blue or white paint finish only) and I recall the modifications to have been as follows:-

• 998 wet liner block
• Gas-flowed Imp Sport head with enlarged inlet valves and Wills Rings grooves
• Imp Sport camshaft
• Pair Stromberg carbs on Sport manifold
• Big-bore exhaust manifold (for attachment to AM silencer)
• Uprated (Imp Sport?) drive shafts and Rotoflex couplings
• Rootes competition RAC springs (Monte Carlo springs that lowered the ride height were an option) with check straps to both front swing arms so that the springs couldn't come out of their seats
• VG95 brake linings

The rest of the car was absolutely standard - gearbox, cooling system, ignition, wheels and tyres - because, I understood, it was expected that each customer would carry out his own further modifications should he wish to do so.

The above description does not accord very closely with the descriptions of the mods listed in Hartwell - The Imp Site, which intrigues me as I understood my conversion was the least expensive and most commonly bought one offered by Hartwells at that time. It was certainly great fun to drive after I had made my modifications although it was noisy and short on creature comforts.

Regards
Andrew Marsden

Andrew Marsden
June 9, 2010

I've been searching for photos and have found a couple of competition ones that show just how standard the car looked (it had to look reasonable, as I used it for visiting all sorts of business in my work as an Officer of Customs & Excise!)

What a lot of questions to consider. Yes you can quote me but only as "I remember ..." since it's almost 40 years ago.

The further mods I made to the car were directed to making it suitable for the fairly serious road rallies, which were run at the time and as far as remember consisted of:-

• Negative camber kit for front suspension
• KONI shock absorbers all round
• Dunlop alloy wheels 5X12
• Kleber 165X12 tyres (originally manufactured for NSU Works rally team)
• Lamp bracket with 4 7" lucas lamps, 2 fog & 2 spot – halogen bulbs
• Halogen headlamps
• Leather rimmed Momo steering wheel
• Pair of bucket seats
• Full harness seat belts
• Map reading lamp
• Power output socket (for the map magnifier)
• Rear roll cage
• Glass-fibre engine cover with suitable ventilation slots
• Reversing lamp
• Oil cooler
• Sump guard covering engine and transaxle
• Aston Martin silencer slung sideways across the rear end (standard wear for rally Imps)

I never had the power output checked, but it would live with a standard Cooper S, but not with the heavily modified ones one usually encountered (at least, not on the straight bits). But carrying full rally gear, two up and with a Ford Anglia engine we were delivering in the back, it made an MGB look very silly in a traffic-light grand prix

I only ran it for two years before I had to sell it (converted back to standard form) to fund a house purchase, but I tranferred all the mechanicals into an old Imp that I already owned, and continued to campaign that, until it started to come apart at the seams, when I bought an Imp Sport and transferred everything again. Old rally cars seldom die, they keep getting transplants.

I'm afraid the only tangible evidence I have, is the photos - no brochure, no bill of sale - which I now see as a real downer.

I hope this has helped you

Regards
Andrew

THE HARTWELL IMP Stages 1,2 and 3 available on 875 c.c. Group 4 available on 998 c.c. SEE ROAD TEST REPORT OF THIS MODEL IN THIS ISSUE 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: -   A GEORGE HARTWELL LTD. ENTERPRISE 35/41 HOLDENHURST Rd. BOURNEMOUTH Tel: BOURNEMOUTH 26566

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

Group III engine conversion

Black & yellow CLJ 195C in 1965

• engine gave the impression that the maximum speed could be maintained all day long
• 80-85 mph took less effort on the part of the driver (side winds)
• road-holding was extremely tenacious, even in the wet
• several braking tests from 30mph in the wet, using 75-lb. pressure on the pedal, produced a consistent 87% g !!
• test car was happy to trundle along at 15mph in top gear
• with revs over 4000 instant acceleration was gratifying
• 3rd gear: very flexible; could usefully be held to just over 70 mph (12 mph more than standard). 1st and 2nd gear 10 mph more than standard. Hartwell's claim that 8,000 rpm is possible seems very likely
• Hartwell's own auxiliary facia panel, covered in matching Vynide): electronic rev counter, oil pressure and water temperature gauges - £20, plus £5 fitting
• loud exhaust, but performance matched the noise

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

• modified cylinder head, raised compression ratio
• enlarged, reshaped and polished valve throats and ports
• oversized inlet and exhaust valves
• Hartwell special camshaft
• high-rate double valve springs
• sparking plugs to suit

Costing £53 10s:

• twin Stromberg CD 125 carburetters (incorporating a hand-operated choke control)
• a special four-branch combined inlet/ exhaust manifold
• air cleaners
• high efficiency silencer

The test car also had:

• competition-type front road springs (£8, including checking of the steering geometry plus adjustments)
• 4½J off-centre Singer Chamois wheels, which can take a larger tyre (£2 7s 1d each)
• competition linings (£10, fitted)
• servo-assisted braking (£23, fitted)

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.

Literature

June 1967   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
GRH 5
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.

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
Test

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.

George Hartwell Ltd. (Peugeot)
3 Oxford Road
Bournemouth
Dorset