Any consequences of use or mis-use of these bits of information are all for yourself. In most cases I do not know at all what I am talking about (being not the least bit technical) and in any case I take no responsibility for anything on this page (or site for that matter) - Franka
or use the Ctrl-F function to locate subjects
General advice
• Make it a religion to check your oil, water and tyres before you leave home each day and a visual check of wiper blades, hoses and brake lines every time you wash the car.
• If it ain't fixed continuously, it's broke.
- unknown American
• Before working on Imp, switch on brain
• Braille: if you can reach a number in relief or imprinted with you fingertips, but you can't see it as it is behind something, use chewing gum or plasticene to press onto / into it and read the relief/ impression. (e.g. the mastercylinder behind the petrol tank)
To obtain spares or spares advice
Uprating an Imp's engine and handling, according to CCC in 1976
Suspension (the basics)
Brakes
Engine
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Smith, P.H.
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separate file. (file also deals with: Cylinder heads; Head bolts; Head gasket (replacing a head gasket); Flywheel bolts; camshafts; Oils; Thermostat cover; Fuel injection)
Active engine mount for a large amplitude of idling vibration
Return to IndexPiping cold air to the carburettors would have a noticable effect.
Imp Sport air filters (part no. 5044639 / VFA 106) can be obtained from Ryco Filters, NZ or similar small filter companies in the UK. If they are given the old filters, they can strip and clean the metal chassis and replace the paper filter.
I use K&N cones. They are meant for a motorcycle, I think, and they are quite tall. The rear one fits only just (there is thick sound insulation against the engine bay wall above it). I like the look of them.
Every year when my Imp goes for its MoT, the original airbox is put on. (The elbows are the same.)
A K&N (gauze) airfilter for a Saab 99 is nearly the same as the paper filter of an Imp
According to Andy Dawson rule no. 1 for Imps is that the engine is fitted with a paper element air cleaner. "In Chrysler Comps we used to call the lack of an air cleaner an 'instant rebore kit'. Fifty miles on a dry day and the piston rings are as good as non-existent."
A Clan benefits even more from fitting K&N air filters to Strombergs than the Imp. Clan carbs don't get too much air, due to the fact that the standard Sport air box 'spout' is only one inch away from the ABS Clan engine lid, which has no cooling slats. With the K&Ns fitted, there is a noticeable difference - and you don't have any clearance problems either. - Grahame Pearson. - Impressions 1983, Dec.
'Filter socks' from K&N are a good option. They don't flow much more air, but they do keep that sand and dust out of the engine. They keep the insides of the carburettors clean.
Fitting pancake filters to an Imp is not recommended because of the position of the exhaust and the chance of drawing hot air in. Pancake filters get overhot in traffic and cause over rich fuel mixture due to very low air pressure. David Vizard wrote that he found that the standard air box gives more power than pancake filters.
Avoid the 'Speedograph' pancakes with a foam filling and the wire mesh surrounds. They don't protect. K&N pancakes are better quality, but may not be successful, because of the heat etc.
If you insist on using them, at least fit a heat shield fitted.
In a Husky engine bay there are fewer options as to the airfilters that can be used. An adaption of the Imp Sport air cleaner box to clear the rear deck of a Husky: Cut the top off the lid and weld a flat plate over the top; Drill holes at regular intervals around the lid to let air in.
If either of the press-fitted inlet or outlet pipes works loose, it's a nuisance. It may be realistic to use the appropriate loctite or similar glue when tapping it back. Or to take the pump to an engineering shop and have the body threaded.
An AC threaded version does apparently exist.
If the rocker arm spring is not springy enough, and the arm is moving about on its shaft with loads of sideways play, then the pump may get noisy.
The throttle cable needs to bend 90° to activate the carb. I found a 90° curved tubing off a motorbike throttle twist grip proved invaluable - saves the cable from snapping.
M. Parris. - Impressions Oct 1986
There are throttle cables available made of an inner cable of stainless steel, and Teflon (PTFE) outer.
A stiff throttle operation is not economical.
The freeflow exhaust system, used on the Sport, does make a difference to the performance and is well worth fitting if you can get a Sport exhaust manifold. But the exhaust is about twice the price of a standard system.
If the car stalls for no apparent reason, and later on will start and run with no problem,
Leadless
Shelf life of unleaded fuel seems to be very short.
Leaded eventually goes off, but petrol that's a year old can still be used. Unleaded can be as short as a month when the components separate or break down and don't respond to a spark as readily.
You can buy anti-oxidant additive for chainsaws...
If you change over from leaded to unleaded or from unleaded to unleaded with an additive, the timing needs to be reset.
With their high compression engines and cast iron valve seats Imps are not suitable for lead-free fuel. Less lead in 4-star petrol will reduce the life expectancy of every Imp engine. Shell has stated that they do not intend to produce leaded petrol from the year 2000 on.
How to deal with this
Lead substitutes
The Federation of British Historic Vehicle Clubs (FBHVC) is now endorsing four Lead substitute products as being adequate for normal driving. (press release) Twelve out of the forty or so manufacturers that make such additives put forward their products for extensive testing by the Motor Industry Research Association (MIRA).
Each product completed a 70 hour test programme including a 20 hour period of accelerated wear testing at full throttle and full load. Tests were also conducted with normal leaded, unleaded and low-lead petrol for reference purposes.
The four products that passed testing are:
These products must be used at every re-fuelling and used strictly in accordance with the manufacturers instructions. They must not be mixed - once a product has been chosen stick with it.
Millers VSP:
Trade price £3.49 +VAT = £4.10 for a 250 ml bottle for 50 litres of petrol.
There are apparently two versions of the additive: the regular which gives the lead-substitute valve protection and raises the octane rating of regular unleaded from 91 to 97, and a competition version, which raises octane ratings maybe as high as 101.
Australia
During the year 2000 Leaded petrol will start to disappear and Lead Replacement
Petrol (LRP) will become available in Australia. It will be phased in.
Leaded Super (96 RON) will be replaced with LRP (also 96 RON).
There will be no LRP with 91 RON or 95 RON (premium ULP).
Avgas will not be legally available to car owners (due to the reduction in taxes). At least one company (Shell, perhaps) will be selling exactly the same fuel as 'Racing Fuel' in 20 litre drums with the extra tax added to the price. 'Racing Fuel' will be rated at 100 RON and has been recognised by CAMS as 'pump fuel' and therefore usable in normal racing.
Petrol treatment 'engine formula', John Rhodes (who is on the Imps mailing list) is an agent.
Fuel pipe
Clear a blockage of the fuel line by blowing down it with a foot pump, or if that is insufficient, use a piano string.
Classical Gas (Instrumental) / Mason Williams. - 1968
354 k, RealPlayer file
"The ignition is always critical on these high-revving engines and we always recommend using the Lumenition Kit - we swear by that."
-- Ray Payne, Hartwell
HT leads. Copper leads with suppressors in the caps
An HT lead gone to high-resistance (50 Ohm or so) will cause glassy growths in plug gaps. Correct HT leads will give enough energy to the spark, that these deposits will be blown away before they can build up to this level.
Immobilizer
An immobilizer can save pounds on your insurance premium. An article on the What & How by Ian Reeves: Impressions February 1995. - p. 21.
Distributor
There are two lucas distributors: 25D or 45D. Of these there are standard and sport versions - the advance curves differ.
The 25D is better made, although apparently it can suffer from points bounce more than the later one.
There is a distributor cap for the 25D4 that enables you to use push-on leads (Intermotor 44140; the screw-in type: 44720). The push-on type was universal to Rootes cars of the '60s, other than the Imp. Any Minx or pre-72 (?) Hunter should have one.
The Imp one was inherited from BMC - the A and B engines had the distributor coming out of the block at a very low angle, hence the side-entry leads. A distributor of a BL 1000 (m.n. a Morris Minor) can be installed in place of the Imp one. The lobes on the BL distributor cam are more acute. It may give another bhp or so. The unit just plops straight in where the Imp distributor comes out.
A Lotus Cortina distributor with no vacuum advance, gas flowed head
Dwell
Many Imps suffer from a decrease in engine speed when the clutch pedal is depressed, to the extend that the engine may indeed stop when cold. L4 engines seem to suffer more than most.
The fault can lie in the fact that although the timing is correct, the contact points dwell is wrong - due to wear in the distributor. If a dwell meter is not available, a good guess would be to set the points gap at .010" in stead of .015" as in the handbook. But remember the engine will need to to be re-timed after and the carburettor mixture may need adjustment.
Dwell on a Lucas 25D distributor is 60° ± 3°
Dwell on a 45D distributor is 51° ± 5°
Ignition
Ion-gap sensing for engine control / J. Auzins; H. Johansson; J. Nyomt. - Automotive Engineering (US) vol.103 (1993) DV31293, no.9 (Sep), pp.65-68. (Combustion will produce ions.
If a spark-plug can detect these (ion-gap sensing) and use them (the currents of 'em) the information can be used for engine management - misfire detection, knock and pre-ignition detection)
The Ducellier distributer was fitted as an emergency on front engined 930 Sunbeams. When the car was first introduced, no Lucas electronic distributers were available so a few cars were built with a Ducellier CB distributer. The static dwell for a Ducellier is 56 +/-1 degrees. For this distributor to work correctly, the domed points must never be filed.
The Electronic ignition was then retro-fitted by the dealers.
Some of the later 930 Sunbeams used Bosch as part of dual sourcing. Bosch only supplied for Hall Effect type ignitions on Linwood built Avenger/Sunbeams.
Hall Effect ignitions were introduced about 18 months into production to replace the ballast type electronic ignition, which had proved a major cause of roadside breakdowns (due to ballast resistors burning out). Hall effect cars tended to give a lot of trouble with poor starting due to bad coils (mainly made in Spain by Femsa). Fitting a Lucas coil seemed to cure it.
Nick Cleak has recently been using the 'Emerald Cams' M3d system, which is fully programmable with a Personal Computer. This ignition system will also run programmable fuel injection.
Basicly that means you can set any degree of advance or retard at any rpm in 500 rpm steps, at 8 different throttle positions. It is has temperature compensation too, so it will, say advance 5° if the coolant temp goes over 100°C to cool the combustion process.
It is not cheap, but when it does the fuel as well, it does become quite economic. (He got gains of 12% in fuel consumption on his Clan with the ignition system alone - over a comp distributor which has no vacuum advance).
The system is triggered by a fixed electronic sensor in the distributor, either the hall effect type or the inductive type as on the Sunbeam 930 as standard. The Sunbeam type will also trigger most of the electronic ignition modules on newer cars.
You can't really use a Competition distributor with a Sport camshaft. It does work, but inefficiently so. The competition one is only suited to competition use, ie. rpm over 7000 on road use. With the Sport cam, it's best to stick with the sport distributor with vacuum advance.
Starters
The Lucas M35G was much better than the later M35J!
The M35J has aluminium stator windings, and a thin pressed-steel commutator-end plate. Less torque, more current and the endplate doesn't conduct heat away from the bronze bearing, so these chop out, leading to (at first) a funny noise when the starter disengages (a sort of whee-ow sound) -
because the shaft precesses around in the worn bush. The M35G (at least the ones up to about 1965 anyway) have all-copper windings, and a die-cast endplate at the commutator end. So the bearing-bush lasts more or less forever.
Pre '65 Rootes mobiles used the M35G.
Only one advantage for the M35J - it's much easier to reassemble, with its faceplate commutator - no need to wrestle with the brushes!
Spark plugs
Do you ever see a pale green deposit on your spark plugs? This can occure if the flame within the cylinder is slightly too hot. I've seen it many times but I could never work out the cause. This could be used as an early warning of cylinder overheating. You will still need to find the exact cause but it may prevent long term perminant damage. To allow the deposit to form you will need to read the spark plug when the engine is hot and just after a good run. Please respond stating under what conditions this green deposit occures and the basic engine specification
Please send your comments to Gary Harding
Speedy Spares sell a kit with an electronic ignition module of the points-assited type.
Be cautious about guessing spark plug suitability for your Imp. Even when they may appear to be working fine, over a period of time you may be damaging the pistons and valves if the plugs are the wrong heat rating for the engine.
A full page advert in Autocar, 8 May 1964. - p. 898:
KLG Spark Plugs - chosen & fitted exclusively to the Hillman Imp.
KLG - chosen by Rootes for all their cars, after extensive and exhaustive tests. Fitted to Humber, Hillman, Sunbeam, Singer and now, exclusive initial equipment on the Hillman Imp. KLG the all British Spark Plug - chosen for top performance under all conditions.
Rootes choose KLG
S. Smith & son (England) Ltd., Spark Plug & Ceramics division. St. Peters Road, Rugby, Warwickshire.
Clutch
For racing purposes the standard MK2 clutch was adequate although heavy duty and multi-plate racing clutches were also available. The clutch flexible hose was a major weakness sometimes being damaged in engine removal (when it supports the slave cylinder) and usually failed by allowing air to be drawn into the system. This was normally replaced
by a standard Imp brake flexible hose as those were much more reliable.
Rootes manual:
5.5" diaphragm fitted to Mk1 up to B.429
6.25" diaphragm ever after
All lever-type are 'conversions' due mainly to the Morris thou 6.25" being compatible and available.
Laycock units give a light pedal. Borg and Beck item are similarly light.
The master cylinder should be the .325" type.
There are roller type clutch release bearings available to replace the carbon ones. They are a step up.
Although the carbon clutch release bearings may seem fragile, they are what is used in heavy duty industrial machinery, too.
Mailing list items: clutch release bearing system
Return to IndexRotoflex couplings
There are two types of doughnuts.
If a coupling has been removed, refit the coupling in exactly the same position, i.e. the same bolt for the same hole.
When refitting driveshaft doughnuts:
Rotate a drive flange into position where a bolt can be inserted through the flange and the doughnut (this is usually near the bottom of the circle of rotation). After just nipping up the nut, the flange is rotated until the next bolt can be fitted.
When all the bolts are in place they can be torqued up. Torque the bolts to the recommended settings. It is the difference in angle between the drive flanges when they are rotated that seems to pull the rubber doughnut into the correct position to enable the bolt to be fitted.
Make sure that, when fitting the bolts, thay are inserted from the right direction. (see diagram in your workshop manual). Or the next time you want to disconnect your driveshaft, you may find you can't get the bolt out, because the transaxle is in the way.
Early Lotus Elan S1 couplings are identical to Imp ones.
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Trouble has been experienced with the outer Universal Joints breaking up following rust. The best answer is to install replacements with a grease nipple incorporated - ones with a long nipple that can be placed when greasing is a good idea.
The UJs from a Volvo Amazone or 140 will fit an Imp and are of better quality - Swedish manufacturer.
Bill West and his assistant John Lewis (aged 31 at May 1963) were responsible for the transaxle design.
The Imp gearbox
Repairing Imp gearboxes / by Bob Hoare. - Impressions 1986, February (2 1/2 page)
Oil; gearbox
Castrol Syntrax 25W90 apparently works fine.
Transaxle
The Imp transaxle: part 1 / Dave Weedon. - Impressions 1990 Spring, pp. 37-39
An alternative for filling Imp transaxles (in stead of using the bottles that EP80 comes in) can be found in Impressions December 1995, page 31.
Castrol Syntrax is a modern synthetic oil which has all the properties of the thicker EP80, but it is thinner and therefore reduces friction. It makes the gear change easier too. If you have difficulty in getting into 1st gear when the gearbox oil is still cold, you may like to try it.
Transmission
The gear lever movement on an Imp should be short and precise. If it isn't (due to wear) than the cure is very cheap and not terribly time consuming. It will include replacing three bushes and a spring in the linkage. (If you can lift your lever up and down, it needs attention).
Gear balls
The domed rubber half ball which fits at the base of the gear lever can be replaced for a hard nylon lathe-turned Captain Scarlet version. (indestructable)
Support
There is a difference between the right and the left gearbox support. Switching them will place the engine a bit too far forward, which can lead to problems with the gear lever. (And as the rotoflexes won't be in line with the wheel centre, they'll probably wear out sooner).
The other major advantage was the gearbox, the Rootes/Chrysler Competition department Jack Knight of Woking produced a wide range of gearbox conversions from the 'works' semi-close ratio gear set to full racing non-synchro mesh 4 and 5 speed boxes.
These Jack Knight Imp boxes were similar to Hewland racing gearboxes with easily changeable ratios. In the JK gearbox the bronze bush bearings were replaced with needle roller bearings allowing the use of a higher viscosity gear oil.
Correct choice of gear ratios was essential because of the narrow power band (7000 to 9600rpm) of a full race 998cc unit.
It was also essential that the rear drive shafts were replaced by Sport components and the rubber couplings replaced by Lotus Elan parts.
The rear hubs were fitted to the splines on the outer drive shafts using 'Green Loctite' and the hub nuts properly tightened, otherwise fretting would occur between the two parts resulting in a stripped spline.
Jack Knight also made a Pawl type LSD which was not really essential to improve the traction but did improve the handling on tight bumpy corners were the rubber drive couplings would wind up and release and cause rather strange handling.
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The braking system needs regular servicing, checking for worn shoes, replacing brake fluid every few years; adjusting shoes and checking for fluid leaks.
If rear cylinders are not free to slide in backplate, the brakes will be mediocre. If the Imp doesn't see much action, all wheel cylinders are prone to seizing.
After lots of miles the locating pads will have worn out. When the shoes are replaced, remove the wear groves across the pads (<0.5mm - file or grind; >0.5mm - weld or replace). Then lubricate the pads very lightly with a copper-based grease.
On fitting new brake shoes, sand the brake drums lightly on the inner surface, to remove any glaze. (G. Harding, Impressions 95 Nov)
Undoing rusty bleed screws on brake cylinders
First take it off the car.
Cut the top off, put a drill down the rest to take out some of the metal in the shank then get the rest out with an 'easy out', (that is a tapered steel rod with a coarse left hand thread up it, you screw it in and when it tightens up in the hole it pulls the remaining thin-walled bit of bleeder thread out).
Then buy a new nipple, resurrecting the rusty one will always
be a pain to work with in future.
You can install a dual master cylinder system in your Imp, with adjustable front-rear bias. You can get bias bar assemblies from most motorsport suppliers, Demon Tweeks being a good example. You would have to modify the pedal box to accomodate the extra cylinder. Part of the bulkhead will have to be cut back as three cylinders will not fit widthwise.
If anyone has trouble with the front brake assembly, worn-out
cylinders etc: The complete brake system is completely compatible to the Ford Escort from 74-76.
There are two brake cylinder sizes around, 18.06 and 22.02 mm diameter. The smaller ones where used by Ford in the Escort Van, the larger ones in the normal saloon. I think Rootes used the smaller ones (which are a bit harder to get), but anyhow, you could at least swap all 4 ones, and then it's completely new!
They cost around 59 DM incl. VAT in germany.
The rear brake cyls have been used by Ford in the smaller Capri cars (1700 ccm) till '79, on the rear, too. Maybe there are some different sizes, too, I haven't figured out that point yet. But there are only two to be swapped on the rear side, so that's only half as expensive as on the front side :-)
They are all compatible Girling parts from the early seventies, so
someone with an old Girling catalogue should be able to find out where
they used the brake system, too.
-- Carsten Bussmann
renew all dubious brake pipes with rustproof brakelines (eg. Cunifer).
The standard master cylinder can be changed to the Sport one with no problems. The master cylinder is interchangeable on the connections, it is only the bore size of the cylinder that changes. Extra pedal pressure will be required, but you won't need a servo. Lost pedal motion will be less. If you can get the ¾" one: all the better - real good feel in the pedal.
The Sport brake master cylinder is a pretty well standard fittment in all Formulas of Single Seater racing.
Demon Tweeks carry them. They may also do a 0.75 version, which would presumably be even better for travel, but may be heavier. Check the fitting.
For most of the Imp's competition career the standard drum brakes were only modified by changing the brake friction material to Ferrodo VG95. The front to rear brake balance was usually made adjustable by adding a third (0.625 inch dia.) master cylinder and balance bar to the standard pedal box.
Suspension influences braking performance significantly; a matter of inter-axle load transfer and vertical dynamic tyre forces.
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From the start of the Imp in May 1963, there has been one change in brake linings. Ferodo MS2s got fitted to avoid sqeal.
Hard linings (VG95) and a Powerstop brake booster are a very good combination, according to Roger Nathan Racing Ltd. in December 1966.
Mintex brake pads
How to choose brake pads ? - there is no such things a the best brake pad, it's a matter of balance. Maximum stopping power without becoming unstable. Brake bias and valves help to get a balance.
A lot depends on the weight of the car. Use as soft a pad as you can run, while not running into fade due to overheating.
Also hard pads wear the discs more rapidly.
EBC front brake shoes (EBC code 5141) for the following cars: Hillman Imp 1963-76, Ford Esxort 0.9/1.1 1968-74.
Lockheed front brake shoes (LOCKHEED part number KB 1045) Interchangeable with: Ferodo F.294.G-Belaco RG.4294, Mintex MGR.9.
To fit the following: Commer Imp Van 5 cwt 1966-on; Ford Essort 1100 Jan 68; Hillman Imp I, II Californian 1963-76, Singer Chamois I, II sports 1964-70, Sunbeam Imp Stiletto Sports 1967-76.
Discs
Talbot Special Tuning did a disc conversion (expensive).
If you make up a back plate to hold the caliper, you can either fit Triumph Vitesse discs, hubs, etc., with Escort wheels, but that is a tight squeeze. Or you can turn doen the end of the stub axle so Viva discs and hubs will fit. However the idea of discs on the front of an Imp has never really caught on. It may not be of benefit, it only makes it easier to lock the front wheels.
The effort might be better directed towards fitting a servo.
Tim Duffee used to make a disc conversion for the Davrian.
Anybody intending to race their Imp will really need disc brakes as the drums will overheat and fade. With good tyres and suspension then the brake locking should not be a problem.
How to fit disc brakes to your Imp / by Peter Nunney. - Impressions 3 (1983), 8/9 (Sept./Oct.)
6 pages with 6 fig.
If you want to try discs, consider Sierra vented discs front and back.
Graham Cashmore's disc conversion is based on a Fiat X-19 disc that doesn't widen the track at all.
 Door hinge screws in wheel arch |
Early front disc brake conversions were carried out by machining Viva HB or HC hubs to accept Imp outer wheel bearings. Viva discs were available in both 8.4 and 10.2 inch sizes.
As the Imp is rear engined fitting discs on the front alone produced gross front wheel lock even with an adjustable balance bar and was of little or no advantage. In addition the Viva hubs made the front track wider causing problems with wheels fouling the lower front door hinges which are located in the wheel arch.
Only in the late 1970's did suitable 10.2 inch discs become available for converting the rear (originally made for some type of Alfa Romeo ?) and these could also be used on the front. With disc all round and slick tyres the stopping power of an Imp could only be matched by a full race Porsche 911 which had a similar weight distribution.
Servo
A servo won't make your brakes any better, it will just save your legs. A servo is only designed to give a lighter pedal. Imp brakes in standard form are very good. If you are having to press really hard, then it is likely that you are experiencing brake fade. A good improvement can come from fitting genuine Mintex brake linings. Some people don't even like the servo response on Sport/Stiletto models.
If you really want to fit a servo, then it can be fitted on the front R.H. wheelarch as on early sports. Make sure you fit the correct type from an Imp Sport or a Stiletto (unless you know what you're doing). And use the corresponding Imp Sport/ Stiletto master cylinder: a .7" bore (standard: .325"). If a servo is fitted, then it is possible to fit harder shoes. This might (or not) improve braking performance.
A Lockheed Powerstop Servo can be fitted in the front. It is compatible with the normal Girling unit of the Sport, which is no longer made.
Brake servo repair kit
from Norton Classic Servos (about £35 ?).
It seems like a fairly straightforward rebuild, being mainly the replacement of some rubber items.
Put the servo in a bucket when undoing the nuts etc, as there is usually a residual amount of fluid left inside.
There was an article on rebuilding servos in Practical Classics a while back and they seemed to think that these nuts and bolts were unobtainable. Use penetrating oil to try and get them shifted. (Wire-brush them first ?)
Norton Classic Servos also sells reconditioned servos that works and looks as good as new (about £100 ?). They can supply both early and late types and they take postorders.
0494 - 56 22 35
www.stoptech.com/technical
Stoptech is a brake manufacturer. Their technial information section has some valuable white papers.
Bearings
From an SKF bearing manual, 1973, which listed the Imp
| Front wheel inner Front wheel outer Drive shaft front Drive shaft rear Main shaft or pinion front Main shaft or pinion rear Differential right Differential left Rear wheel inner Rear wheel outer | K-L 44649 / K-M 44610 K-LM 11949 / K-LM 11910 6204 / C3 410425+BMN. BRH 162112 K-21075 / K-21212 K-LM 48548 / K-LM 48510 K-LM 48548 / K-LM 48510 K-LM 67047 / K-LM 67010 6006 / 31 414228 |
Differential
In a race or sprint car or even a road car that sees uncommon sporty use, the standard differential can shear the cross pin or snap off at the root of the bearing carrier. This happens more often with non-tarmac competition Imps.
A limited slip differential won't do this. Another (cheaper) prevention method is to heat-treat, polish and tuftride the carrier and pin.
For corners that you would take in 2nd gear (where the rotoflex couplings tend to wind up and snatch), a limited slip differential would improve handling.
Types of limited slip differential:
JK pawl
Brake lights
Stiletto brake lights are supposed to work with the ignition switch off.
Brake fluid
Silicone brake fluid is marvelous. Being non-hygroscopic (as in: it
doesn't absorb water) its boiling point will remain as it is; it won't
corrode the steel brake pipes or the wheel cylinders. (advises G. Pearson) Ordinary brakefluid sucks up water dramatically. Water in the system will lower the boiling point of the fluid and it will create corrosion. If you do not know whether the brake fluid in your Imp has been replaced at the appropriate intervals then the condition of the brake pipes is uncertain. With ordinary fluid you have to change it every so often, while the silicone stuff is a fit-and-forget thing.
When switching to silicone fluid it is essential that all wheel/master cylinders etc. are either replaced or overhauled. (adds M. Jones)
Rootes Service Bulletin RSB 61-232: Braking System Fluids April 19, 1961
Return to IndexSteering wheel
Andy Dawson recommends a 14" steering wheel. It will take less strength to park the car. But the real benefit is over bumpy roads and on long journeys where it is more comfortable and doesn't jarr the hands over road irregularities.
Seats
DAF 66 Marathon or Volvo 66 seats fit straight on
Mk2 Fiesta seats fit with hardly any effort. The backs fold forward, which is handy.
Peugeot 405 seats are very similar size. Perhaps they are made by the same people as the Imp seats?
Dashboard
Don't try to fit a Rally Imp dash (CTS 1502) to a Mk I Imp. It involves more drilling and cutting than you think. Fitting one to a later model is easier.
Nadadash used to make an aftermarket dashboard for the Imp, called the Impanel.
Chrysler Comps./ Talbot Special Tuning did a special dash until well in the 80s.
Imp Rootes Accessories obtainable from Rootes dealers included an Instrument Panel which fits under the heater control and consists of a tach, ammeter and oil pressure gauge.
For a stock 1964 Sunbeam Imp Deluxe, you could choose a small Smiths tachometer, as fitted to early Avenger GT (1250 and 1500).
It is said that M*** Cooper speedos and tachometers fit the Imp Rallye Dash.
Vince Frost @ Merlin Motors (on 01352 - 720 280) has had a batch of paint made up to the original Rootes off white colour.
Seat belts
Inertia-reel seat belts. How to. Impressions December 1995, p.32. And another how-to for Huskies by D. Couldry. - Impressions 8 (1988), no. 4.
The Imp's seat belt arrangement was updated by my father in 1974 see '07/74 seat belt adjustment' in the patents section. Brian's was not a model specific role, his engineering went across the board in this instance as part of his interest in raising safety standards.
Three point harnesses
A three point harness going back to the rear wheelarch tends to pull you over to one side, a four point harness is probably more comfortable.
Four point harnesses
Three mounting points
Without a rear seat: Full (4 strap) saloon harness are mounted at three points with the 3rd mounting hole drilled into the load platfom (or rear seat area). An accident restraint loads on the mountings must be carried by the sheet metal in shear (as far as is possible). Normally this means using the eyebolt provided with the belts straight through the load platform with large plates sandwiching the sheet steel.
Do not mount the rear strap to the original side mounting as this would pull unevenly.
Four mounting points
While you can use a four point harness by crossing over the two top straps and securing them to the lower points, this is not a really good idea. Adding the shoulder straps to to the original floor mounts (that already hold the lower harness straps) would double the load on these points. Also it would be very hard to tension correctly a belt which performed such a U-turn.
RAC competition regulations, the Blue Book: 'The fixation points to the rear should be positioned so that the strap from the shoulder is as near horizontal as possible. It should not be located on the floor directly behind the driver/co-driver' It also says that if there is one rear mounting it should be 'symetrical for the two shoulder straps'.
Damage repair
When an Imp rolls, they tend to twist.
Straightening out a bent Imp that got frontal impact damage isn't easy. I did it with mine. It cost me lots and I'm not entirely satisfied with it. It did pass the thorough test it had to go through, before I could ask the papers back (it had been totalled) and put it back on the road.
If you are really attached to the car, the best and safest method of keeping the spirit of the car alive is to re-shell it (99.9999% of competition Imps have been reshelled at least once in their 'careers'). Unfortunately, the only shells that are available now are s/hand ones and that is something that the DVLA officially don't like. However, having reshelled a fair few Imps, I can say that it can be done legally and safely.
Avenger armrests
Top plates
A how-to by G.Harden (Impressions 1988, no.5) describes how repair a damaged top plate (1st sign: holes above the
petrol tank lip just above the top-plate bolt heads) and how to improve on the design.
Heater hose
Heater hoses on an Imp are 5/8" internal diameter rubber hose - an unusual size for repair using 15mm copper pipe. However if you solder a 15mm Yorkshire fitting on the end of the pipe, the solder rings on the fitting make the size up exactly. In fact, I am sure the elbows on the heater unit are basically Yorkshire fittings with rings on, too.
says Nigel Frosdick in Impressions December 1997
Check condition of heater hoses and renew any doubtful looking ones, before they start to give trouble. -service item
Here's the How-to by Peter Nunney.
Washer
To thaw the washing liquid in your washer system in winter, have the tubing winded around the heater hose. (mentioned by G. Pearson)
Put the windscreen wash reservoir bag up against the passenger bulkhead (towards the offside of the heater). The bag will rest on the heater inlet hose and be supported by hooks or stiff wire from the cardboard retaining clips. In this position the bag won't freeze as easily and will thaw when the engine runs.
Wiper spindle rubbers
The wiper spindle rubbers are easily fixed. Remove the wiper and undo the retaining nut. The remains of the rubber can then be removed.
Obtain some wiper spindle seals from a Volvo 340, the earlier the better, as these have a chrome seal... much nicer and a fit-and-forget part.
Imp wiper blades were the same as for Humber Super Snipe or Hawk 1959-62.
DL3W or a 15W
The 15W is the one with the big cylindrical motor casing and permanent magnets. The DL3W has a wound field, and a peculiar-shaped housing and, if not used for a while, no sign of magnetism.
The difference? The 15W needs 2-way switching to prevent it over-running the park switch. The DL3W only needs simple on-off switching.
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