1400cc to 1800cc........


Home   1400cc to 1800cc Modifications Technical   Red Cat SLR No.77 Le Mans Links

Converting a 1400cc K-Series Caterham to 1800cc

Between 1991 and 1996, one of Caterham's most popular engine installations was the 1400 Rover K-series, in both "standard" and "Supersport" form. In fact in 1994, more 1400 K-Series engines were fitted to factory built cars than any other configuration.

Although a comparatively powerful engine for it's capacity and undoubtedly a very sweet performer in the Caterham, particularly when coupled to Caterham's own 6-speed gearbox, the Caterham chassis is capable of running with much more power and particularly an increase in torque over that offered by the 1400.

Caterham realised this, and from 1996 onwards dropped the 1400cc unit in favour of it's bigger capacity siblings - 1600cc & 1800cc. This has however left the 1400 a particularly good value car - after all the 1400K cars are all fuel injected and De-Dion chassis, therefore comparatively well specified when looking at alternative derivatives. So what would be involved in taking a 1400 K-Series Caterham, and dropping in the later 1800cc unit to bring the car more "up to date"?

Having owned my 1400 Caterham since 1998, in late 2002 I decided that this was the route I was going to take. The resulting task turned out to be more straightforward than I had initially thought, and very cost effective. Locally, there are 3 of us with Caterhams (2 originally built as 1400 “C” Class racecars) that have now done the conversion.


The detail....

When the Caterham was revised in 1996 to become 1600 or 1800, there were changes made to the post 96 cars with respect to wiring, engine management etc. Converting to post '96 wiring is a major job, but it is possible to change a pre-96 1400 to become 1800 by changing the mechanical bits, and "tricking" the engine management into believing it's still running a 1400, by retaining the existing crank trigger signal (flywheel) but using higher capacity injectors. The areas needing attention can therefore be divided as:


Bottom End:

Rover K-Series engines share 2 common crank sizes and 2 common bore sizes enabling the 3 capacities (14/16/1800) to be achieved:

  • 1400 & 1600 share the same crank (stroke)

  • 1600 & 1800 share the same bore & liners

However, unfortunately the 1400 K-Series engine used by Caterham is of the “wet-liner” type, rather than the “damp-liner” type of the 1600 & 1800 derivatives. Despite commonly being suggested, it is not possible to fit the bigger liners of the 1600 & 1800 engines in the smaller 1400 block. The wet liner block of the 1400 is evident by a “cross webbing” on the flat side castings, with the liners suspended from the top face. The damp liner blocks of the 1600 & 1800 engines have “bulges” cast in the sides that allow for the bigger stroke of the 1800 crank – not flat sided and no cross-webbing. There are 1400K “damp-liner” engines around, but these were not standard fitment by Caterham.

It is therefore necessary to source a complete 1800 bottom end (block, crank, rods & pistons) to achieve the conversion to 1800cc spec.

The whole lot can be bought s/h for anything between £150 and whatever you’re prepared to spend. MGF engines are a good starting point, but any 1800 K series is fine – Freelander, Rover 200 & 400 series, Elise, etc. The VVC is fundamentally the same bottom end as the standard K-series, but comes with a much better flowing (and hence more valuable) head if included in the price. Around about 2001 steel dowels were fitted to ensure better mating of the block to head join, but any engine can have the steel dowels retro-fitted. This is simply a case of pressing in the new dowels with a soft mallet. 

(back to index) (top of page)


Modifications to the block etc to fit the Caterham:

1. Spigot bush and bearing: Usually the spigot hole in the crank (flywheel end) is approx 22mm diameter, but worth checking because one owner discovered the hole to be only 10mm bore! The 22mm is the size that mates to the Rover gearbox for the transverse engine installation. In the Caterham, the Ford gearbox is used which has a different diameter input shaft to the Rover transverse gearbox, and hence the need for a new spigot bearing and bush. These are available from Caterham or QED for approx £25 (together). To fit the bush it may be necessary to clean out the 22mm hole in the crank - gently Dremmel or similar until the bush is a tight but push fit, but use Loctite if necessary. The bush should be gently driven in using a wooden block (or similar) until the bush is flush with inside edge of the crank hole, effectively creating a smaller bore crank.

The spigot bearing is then pushed into the new hole (again use Loctite if necessary) with the rubber seal outermost. During vehicle use, the bearing is only functional when the clutch is depressed, allowing the gearbox input shaft to rotate independently to the crank. During normal running with the crank and input shaft rotate as one.

2. Starter motor fitment: It is necessary to grind the web from the side of the block where the engine number is shown. A substantial amount of the end web must be removed, and also part of the next web along which may have a threaded hole through the middle. The amount of work to be done can easily be copied from the old 1400 block, but if possible, remove the bellhousing from the gearbox (4 bolts on middle inside) enabling a trial run with the starter motor fitment before trying to drop the engine back into the car! If intending to replace the starter motor to the new underslung-solenoid type, be aware that it is necessary to remove a greater amount of the web.

3. The engine number (copied from the rearmost web before grinding!) should be stamped onto the top surface of the bearing ladder (level with center line of the crank) using a 3mm letter stamping set. Examination of the old 1400 block will show exactly where Caterham will have stamped the old number. 

(back to index) (top of page)


Top End:

All the 1400 head, cams, pulleys etc can be retained – but it should be the later "high port" head. Older low port heads have smaller diameter ports and hence less ability to flow – not suited to the 1800 requirements. Fundamentally there is no difference between the later (high port) 1400 heads and the 1600 & 1800 ones - all are the same K16 head – same inlets, ports, valves etc. This is the major reason why the power figure for the 1800 is not much greater than for the 1400 – only approx 10 bhp difference. The 1800 is stifled somewhat by the lack of breathing allowed by the standard head.

For lots more info refer to Dave Andrews pages on the K-Series engine: http://members.aol.com/DVAndrews/kengine.htm

When removing the head, the whole assembly can remain intact – including the cams. The cams are retained using a “cam carrier” which is mated to the lower head section. These are “matched” and if for any reason need to be separated must remain as a pair.

(back to index) (top of page)



All K-Series Caterhams run "similar" flywheels, based around the Rover 1600 item (smaller than the 1800 which will not fit in the Caterham bell housing) The only difference with the 1400 is the "number of missing teeth" pattern that sends a signal to the MEMS – the sensor is at the small green plug below the inlet / plenum. The sensor uses the missing teeth pattern to send a signal to the ecu (Rover MEMS) in order for the ecu to know the rotational position of the crank – hence the flywheel must be matched to the MEMS unit. 1400s use the Rover-36/2 pattern (2 missing teeth) whereas 1600/1800s are the Rover-36/4 pattern. Retain the original flywheel (or same type) and you can retain the 1400 MEMS.

Caterham have recently been selling the lightweight flywheels for £100 (inc.vat), which is a worthwhile modification. These are the same as the current 1800 version (£250!) excepting the missing teeth pattern. My original flywheel had evidence of fine cracking in the pressure surface, therefore I decided it would be better to renew.

(back to index) (top of page)



The Rover injectors are colour coded. 1400s generally have blue injectors, 1800 have "straw" (cream) ones. In order to create the fuelling needed for the 1800 engine, it is necessary to source the straw coloured injectors. Although the new engine will be 1800cc, the MEMS will think the engine is still 1400cc. The additional fuelling from the injectors will accommodate the increase needed for the bigger engine. Cost of these should be approx £50 second-hand.

The 1400 fuel pressure regulator can be retained in the conversion rather than using an 1800 version – it’s the black disc shaped item at the front of the fuel-rail with a vacuum take-off. An 1800 fuel pressure regulator gives a slightly higher fuel rail pressure than the 1400/1600 ones - some owners who have fitted the 1800 version have found the mixture to run too rich and have reverted back to the original 1400 FPR.

(back to index) (top of page)


Generally it is believed that the standard clutch is fine for the 1800 conversion. However, whilst the engine is out, consideration has to be made to fit an upgraded clutch. I understand that Caterham now use the AP comp clutch for all models. I fitted an AP comp clutch because I knew I'd go for more power later and I didn’t want any danger of slip. If it needs to be changed again it’s engine out! An alternative to the AP item is a Helix clutch from MardiGras Motorsport, cheaper if trying to save a little more cost. The Caterham clutch plate is a “special” from AP with upgraded springs and can be used with a Helix or AP cover section – totally interchangeable.

(back to index) (top of page)



Various gaskets are needed to do the job. A head set (top end bits) and conversion set (all others such as oil pump etc) from DVA cost approx £85. The head set includes the necessary steel dowels to replace the weak plastic ones fitted to Rover engines until around 2001. This aids the prevention of head gasket failure.

(back to index) (top of page)


The gearbox!

Usually a section of the gearbox input shaft needs to be removed (I did 16mm) due to the hole in the end of a 1400 Caterham crank being bored slightly deeper than Rover engines for other uses - Caterham now use shorter input shafts in the gearboxes. The excess length originally just rotated in free space so it saves a few grammes weight!!! Alternative is to have the crank bored to suit, although this would require using a machine shop and will not be of any great benefit.

The input shaft can be shortened using an angle grinder with a steel “cutting” disc fitted. Put the car in gear to stop the shaft rotating and cover the surrounding area to prevent damage from flying sparks! It should only take around 5 – 10 minutes to remove the excess.

(back to index) (top of page)


Other points worth noting:

  • It is helpful to beg/steal/borrow 2 engine stands, enabling the units to be side by side when swapping all the bits over. Additionally, remove the engine without the gearbox – it’s much easier!

  • Clean everything that comes out with a toothbrush and WD40 or carb-cleaner – it’ll be like new!

  • Identify all the main points where the engine loom must be disconnected to remove the engine, using a coloured cable-tie. It’ll make subsequent removal really quick if needed.

That's it - and could probably be done by most practically minded owners.

I started by talking to Dave Andrews, and ended up buying an engine from him. He guided me through a rebuild - stripping, re-ringing, new bearings etc. Dave is an amazing engine builder - it's worth doing the rebuild just for the "race engine building experience" he puts you through. Cost me a little more in the end but I was pleased that I'd effectively got a "new" engine.

Somewhere along the line I caught upgraditis, and have since fitted throttle bodies and an Emerald ecu. Once converted to 1800, there's loads of s/h bits available that otherwise would have been no use on a 1400. Another benefit of the Emerald is that it’s possible to retro fit a Rover 5AS immobilser unit complete with “plippers” – a useful upgrade if there isn’t an immobilser fitted.


And finally …….

  • There doesn't appear to be anybody who's done the job and is running a cat, although my engine ran so sweetly that I'm not sure it's a problem. Most 1400s are of an era pre-cat and emission testing.

  • One owner has had oil aeration/starvation issues. This appears to be related to fitment of a new pump, flowed to give better capacity and pressure, but with the downside that the ability to get the oil to the top of the engine has increased, with no improvement in getting it back to the sump (gravity!). The result is a very low running level in the sump. Trials using a slightly shorter pressure release spring have solved the problem, reducing the hot running pressure of the engine slightly. The engine is currently running at approximately 3.6 bar hot, compared to a previous 4.0 bar.

(top of page)


Important Disclaimer:

All information given herewith is given in good faith and is a statement of facts believed by the author to be accurate at the time of writing. Use of the information directly or indirectly is at the users own risk.






www.superse7ens.co.uk © 2009     contact: webmaster@superse7ens.co.uk