design - Land Rover section


An introduction to Series Land Rover engine conversions

Some thoughts


Note that this page is written from an American perspective
There are several suitable engines not mentioned because they were never sold into the US and they are difficult for Americans to obtain

"To be honest, there is no 'best' engine. The choices are so varied it is impossible to choose. Some are easier to fit, some are more economical, some are more powerful, some are too powerful and will break the Land Rover, some need other mods to make them work and others drop straight in." Mark Rumsey, 2007

Series Land Rovers are often described as woefully underpowered for facing the great expanses or for modern highway traffic.  Land Rover specs the Series III 2.25L engine with 8:1 head at 70 hp@4000 RPM and 120 lbft @2000 RPM. The 2.25L diesel is spec'ed at 60 hp@ 4000 RPM and 133lbft @1800 RPM.  I jokingly used to tell people my 109 Dormobile could go 0 to 60 MPH same day, assuming no headwinds or uphill sections.  Its no wonder that people who actually put lots of miles on their Land Rover often start looking for engine conversions.

A high percentage of series engine conversions seem to be poorly done by good people who are a little unclear of what needs to be done or what works.  This web page is an introduction to conversions that I have seen or read about over the years and my thoughts about Series Land Rover engine conversions in general. My goal is to provide a knowledge foundation of the Series Land Rover drive train and engine bays, provide some ideas of what kinds of engine conversions are known to work and provide an idea of what needs to be done to make them work.  Please do not let my ideas of what works and what doesn't limit your thinking. A good fabricator and or a different approach can often produce new and better solutions.   I have additional web pages that go into specific engine swaps in additional detail.  

First some very basic thoughts: Modifying a 2.25L engine with 9:1 compression, 2.5L cam, Rochester B series carb and a performance distributor curve can add another 10 to 15 HP to the engine.  A full out expensive performance upgrade to the larger 2.5L petrol engine that includes a modified cylinder head  and other high dollar items might get you to around 115 HP.  If a  power increase of 10 to 25% will be enough to meet your driving needs, you should give converting to a 2.5L petrol engine plus performance upgrades a try.  It will be by far and away your easiest conversion.  On the other hand a stock 200tdi will give the same HP as a highly modified 2.5L petrol engine but with more low end torque and better fuel mileage.  Rob Davis makes a conversion based upon the well regarded Mercedes OM617 turbo diesel engine that is about as close to a drop in turbo diesel conversion that you will find.  It is a proven design and all the engineering is done for you.  This conversion is well worth considering and probably the finished price would be less than a conversion you home engineered.   These are your easiest to engineer, easiest and quickest to install, probably least problematic and likely cheapest engine swap possibilities for a 4 cylinder Land Rover conversion.

If you choose an engine that fits in the stock engine bay and puts out less than 140 HP and 160 lbft torque , you can stay with the stock Series gearbox and just do an engine swap with rear axle upgrade.  This is usually well within the abilities of an experienced home mechanic.   If you want anything more powerful you need to think in terms of complete drive train upgrades and possible suspension upgrades.  You suddenly get into the world of drive train engineering and custom fabrication design.

WARNINGS:  Before you begin, understand that engine conversions are not cheap, nor are they quick and there are always teething problems getting everything to work together reliably.  It will cost more than you think it will, take much longer than you think it will and you really do not want to add up the costs of everything you buy for the conversion, especially if you are married.  Unless you are a well known Land Rover engine conversion specialist, chances are good that the resulting vehicle's resale value will be less than that of a pure stock vehicle and if you do the conversion poorly it may not off road as well nor be as trouble free as stock. If you are making the conversion to save on fuel costs, it is probable that you may not  recover the conversion costs in fuel cost savings during the time you own the vehicle.  You may just be paying the money you might save on fuel over the years now on the conversion instead of later on fuel. Run costs vs savings numbers first.

Done right, an engine conversion can make your Series Land Rover safer in traffic , cheaper to operate and maintain, more capable and more reliable. Properly done, they can be a vast improvement.   Poorly done or done on the cheap, the conversion can be an ongoing nightmare.   Think twice before going down the engine conversion pathway, save up lots of cash before you start the project and if you make the decision to proceed with a conversion, analyze how every changed part might affect every other part of the drive train and suspension before spending your first penny for parts.  When you find yourself roaming auto wrecking yards, don't forget that those vehicles are there for reasons that may include the functionality of the part you are looking for.  Also used parts sold on ebay, may or may nor be within spec and may or may not be from the year & model the seller say it is. As an example when I converted my 302 V8  from carburetor to EFI I ended up with a DOA computer box, bad air bypass valve, partially clogged injectors, incorrect throttle body and a MAF sensor that went out of spec within the first 5000 miles of driving.  All these parts were purchased on ebay.  I spent the extra money for a rebuilt 302 long block and started off with a 3 year, 30,000 mile engine warranty.  The engine has been trouble free in 8 years of driving.  And of course there were lots of teething problems that needed to be addressed when the conversion was completed.  Don't expect to make complex modifications and drive off trouble free without your tool box.  Lastly, document everything so you know what parts to replace as things wear out.  You should at least have a part number list you keep on the vehicle with tune up, belt and hose part numbers.   I considered an important part of my EFI conversion to be a set of wiring diagrams for my conversion showing what is actually there along with wire colours and pin connections.

What we begin with

As Series Land Rovers evolved they came equipped from the factory with 4, 6 and 8 cylinder engines. Almost all of the series Land Rovers imported into North America by Rover had four cylinder power plants. The six cylinder was available in 109 station wagons the last year that 109s were imported to North America and have remained a rarity here. The series V8s, the Stage I, were never imported to North America by Rover.

4 cylinder petrol
The 2.25L (2286cc) 3 main bearing engine came in two versions, one with a 7:1 head and one with a 8:1 head.  Early versions all had 7:1 cylinder heads. I have a FAQ web page that explains how to tell a 7:1 Series Land Rover head from an 8:1 cylinder head. In 1980 the 3 main bearing engine block was replaced by a stronger 2.25L 5 main bearing engine block.  Land Rover used the same basic engine for both a petrol engine and  a diesel engine.  The 5 main bearing version allowed a turbo to be used on the diesel version.  Starting in 1985, Land Rover stroked the crank (longer throw).  The new crank increased the engine displacement to 2.5L (2495cc), adding additional torque at the low end and increasing power from the 2.25L's 70 hp@4000 RPM and 120 lbft @2000 RPM to the 2.5L's 83hp@4000 RPM and 133 lbft@2000 RPM.  This was the last and most powerful petrol four cylinder engine that Land Rover built and sold.  The 2.5 was discontinued in 1990 when the 200tdi was introduced.  A 2.5 cam will fit into a 2.25 engine and is a performance upgrade over the stock 2.25L cam.  If one were to do a performance rebuild of a 2.25L engine, a 2.5 cam and raising the compression to 9:1 should be the first steps.  Sourcing a 2.5 engine and raising the compression to 9:1 would be a much better option.  A performance 2.5 engine with 9:1 compression, 30 over pistons, ported and polished head, street cam, and headers might get as much as 115 - 120 HP.  As  comparison, a stock 200tdi is factory rated at 111hp@4000 RPM and 146lbft@1800 RPM.

6 cylinder petrol
There were several versions of the Rover six cylinder engine. The following information   comes from Dr James Taylor "The 3-litre version was designed FIRST, for the 1958 (1959 MY) Rover P5 3-litre. They needed 3 liters because the car was competing higher up the market than the P4, and they needed 7 bearings to improve smoothness for that market. So the bore centres were repositioned and it ended up as very different from the original 2.6 IOE engine (2638cc) in the P4.  The short-stroke engine (2625cc) was developed from the 3-litre as an improvement (smoothness, also manufacturing cost) over the earlier 2.6. Rover did try the 3-litre in Land Rovers but found that the high torque could cause transmission problems and that the fuel consumption was higher than they wanted. So they went for the 2.6.  The original 3-litre and 2.6-litre engines were upgraded with a water-heated inlet manifold and other modifications in 1962. These are known as the Weslake-head versions because tuning expert Harry Weslake was consulted, although Rover engineers insist that most of the design changes were their own. All the 3-litre saloons went to the Weslake-head engine because they needed the extra performance. The Rover 95 (P4) kept the 100 engine (give or take a few tweaks) and the new 110 took on the Weslake-head 2.6. There were also very small numbers of 2.6-litre (and even 2.4-litre) versions of the Weslake-head engine used in the 3-litre body for overseas markets.

The NADA 109 Station Wagon was the ONLY Land Rover to use the Weslake-head 2.6 engine. All other six-cylinder models used the earlier (Rover 100) engine, although improvements were made to this over the years until production ended in 1979-80. The Weslake-head engine was fitted for the US because Rover North America's head, Bruce McWilliams, insisted that Americans wanted the extra performance."

So the obvious power upgrade for a Land Rover 2.6 engine is a late Rover 3.0 engine.  More power, it is almost a direct bolt in replacement and takes an engine expert to tell the difference between the two.  The down side is that the Rover six cylinder engine has been out of production for a long time and some parts are getting hard to find in the UK.

8 cylinder petrol
The Aluminium 3.5L (3528cc) V8 was developed in the 1950's by GM for use is its Buick model line.  When GM discontinued the engine in 1964-65, Rover purchased the rights and tooling to replace  its aging 6 cylinder engine line in their automobiles. Rover first used the engine in the Rover P6. A detuned version of this engine was introduced into the Land Rover product line (with LT95 gearbox) as the Land Rover Stage I in 1979 through 1985.  The engine was detuned to 91hp@3500 RPM and 166lbft@2000 RPM (Rover engineers didn't want the Stage I going faster than 65 mph).   The early Range Rover version of the 3.5 was 130hp@5000RPM, 185lbft@2500 RPM. The last version of the 3.5 used in a Range Rover was factory spec'ed at 165HP@ 4750 RPM and 206lbft @3200 RPM.  Except for the Stage I, the power specs provided for Range Rover and Defender versions of this engine, from 3.5 through 4.6 L versions, is at much higher RPM levels than would be used for off road travel.  The lack of low end torque and poor fuel mileage on premium petrol is why some folks remove the 3.9L V8 from their defender and replace them with a 300 tdi. Things to consider when considering swapping a Rover V8 into a non-V8 Series Land Rover is that parts are expensive, that the heads are easily damaged from overheating and that in The United States, the engine is likely to require SMOG testing after being placed into a Series Land Rover with the entire Series Land Rover needing to meet the emissions spec for the year the engine was built.   Going up in the 3.5/3.9/4.0/4.2/4.6 engine family is the obvious power upgrade for a Stage I.

Engine bays
There are 3 different engine bay configurations on series II and Series III Land Rovers (I will not be going into any of the forward control Land Rovers). 

The standard 4 cylinder engine bay is basically a small rectangular box, 33 to 34 inches wide depending upon where you measure, 33 inches between the bulkhead and the front cross member and about 29 inches between the bulkhead and the radiator which is mounted to the rear of the front cross member. There is 39 inches between the bulkhead and the radiator bulkhead to mount the engine, radiator, radiator fan and inside mounted headlamps.   The frame rails are only 25 inches apart but you only have about 15-1/2 inches between the left frame rail and the front propshaft in order to clear the front yolk. Adobe Acrobat file showing dimensions of a 109 frame.

The easiest upgrade would be from a 2.25L engine to the 2.5L LR four.  Next easiest for a petrol engine rig would be a pre-engineered Rob Davis conversion. He has engineered the adaptors and which optional parts go with which to create a powerful, reliable 2.5L GM four cylinder upgrade.  Just buy the engine from Rob and mostly just bolt it an and drive.   This swap adds a lot more HP than you can get out of any of the LR petrol fours. This is probably the best bet for someone who isn't an experienced fabricator.  I think the next easiest conversion would be a 200tdi engine from a Ninety or One Ten.  These can be made to bolt to Series gearboxes but heads and manifolds are NLA and getting scarce. The Mercedes 616 2.4L diesel from a 240D is an easy swap using the adapter from Seriestrek.  The HP is close to that of the 8:1 2.25L petrol but it does not have as much torque as the LR fours.   However it is a comparatively easy swap and the engine tolerates used french fry oil quite well.   The 300tdi and the International Harvester 2.8L diesels are designed for different bell housing patterns.   There are a number of other four cylinder engines that can be made to fit without a lot of body modification.  If you are more ambitious and an experienced welder/fabricator there are a lot of V6 and V8 small block engines to choose from.  When you get into the V engines you need to think in terms of centering the engine & gearbox inside the frame (stock is offset to the left).  This takes a little more effort with a 109 than an 88 but is quite doable.

The 6 cylinder engine bay is basically the same as the four cylinder bay with a deeper dished bulkhead.  The 6 cylinder bulkhead has an expanded, deeper dished area to clear the bell housing of the longer inline six engine.  This also means the six cylinder Series Land Rover has different floor boards and gearbox tunnel than the four cylinder Land Rover.   The six cylinder engine uses the same bell housing as the Series I four cylinder engine.  The transfercase cross member is moved rearwards 2(?) inches from the four cylinder position.  Because the six cylinder engine is moved rearwards, the front prop shaft is longer, the rear prop shaft is shorter. 

The engine bay configuration best lends itself to inline fours and sixes.  The easiest swap for a Land Rover 2.6 engine swap would be a Rover 3.0 six.  The engines are virtually identical from the outside.  But parts for these engines are getting hard to find.  The most common swap in the States is to either the less powerful 2.25L four cylinder engine or a Chevy inline six. There are still Scotty adapters floating around to mate a Chevy six or four to a Land Rover.  If the pilot bushing is missing you can buy them new:  Pioneer Inc, Automotive Products  part number PB-50-D-5.  This is a world wide supplier with manufacturing plants in several countries.  The Chevy inline six is just slightly longer than the LR six and the mechanical fan sits a little low for a LR radiator. The starter motor sits very close to the front propshaft.  A geared started motor and a custom narrow diameter front propshaft from Great Basin Rovers can take care of that problem.  Some people have had to add a notch to the front cross member to make the engine fit. Alternatively you can cut the front cross member off, move it forward an inch and reweld it without moving the radiator bulkhead.  This is usually enough extra clearance.   A cross flow radiator sitting on top of the front cross member will also be needed.  Scotty always advises people to use the 250 cu in version of the engine.  He felt that the larger 292 version was too powerful for a Series gearbox.   The Cummins AT6 ('80's bread trucks & UPS vans) is close in size to a Chevy inline six and could be made to fit, as could the LD28 (early '80's Nissan Maxima option).  And of course the inline four cylinder engines would also fit.  The Nissan SD33T (Late International Scout option) might be an option.  It is a long engine but if you are a good fabricator it is worth investigating as there are off the shelf bell housing & clutch components to bolt directly to Borg Warner T-18 and T-19 gearboxes.

The 8 cylinder engine bay has another different bulkhead, dished for a centered V8 bell housing and entirely different floor boards and wider gearbox tunnel.  The radiator bulkhead is moved forward to align with the front wing panels and the cross flow radiator is moved forward (is the front cross member forward as well?) .

I have not measured a Stage I engine bay, but it should fit any of the small block V8's V6's and the four cylinder engines with minimal if any body or frame work beyond possibly new engine mounts or mounts for different gearboxes.

The width of any of the Series engine bays can be expanded by using Defender inner wing panels.  The front cross member can be cut out, moved one inch forward and rewelded without moving the radiator cross member forward of the stock Series location.  It can be moved 2 inches if you mount the radiator bulkhead to the cross member differently. This requires converting to power steering. The power steering conversion also provides additional side to side free space in the engine bay.

Drive train
The Series Land Rover gearbox used with the four and six cylinder engines dates back to 1932 when Rover introduced it for use in passenger cars. Though the gearbox has been updated over time and syncros added, the gearbox is not strong enough to reliably handle much over 120 HP and 160lbft is about the limit on torque.  The Series Land Rover transfercase, on the other hand is a very robust unit capable of handling high power loads. The C and later suffix transfercases are slightly stronger than the A & B suffix transfercases.   The good news is that Advance Adapters now make adapter plates that will mate a Series transfercase to most common American top loader truck gearboxe. What used to be the hardest part of an engine/gearbox swap has now become an easy bolt on. This both greatly simplifies a conversion and reduces costs of a conversion. I now have a web page providing details of the adapters for the Series transfercase.

The Rover 10 spline axles were plenty strong for Land Rover's original 1.6L engine in a light weight series I body. But they do not stand the test of time pushing a heavier series II or III body with the more powerful 2.25 or 2.5L petrol engines. The heavier 109s frequently break axles when used under rough conditions. Rover addressed this by using an ENV axle on their heavy duty Series IIA 109 options then making the 24 spline Salisbury axle standard equipment on series III 109s. A Salisbury is a version of the highly regarded Dana 60 light truck differential made in the UK under license from Dana.

When Rover developed the Range Rover they stayed with the lighter duty 10 spline axles. They designed the Range Rover to be full time four wheel drive specifically to distribute the engine's power among the front and rear axles. This puts less stress on the rear axles and makes them a lot less apt to break. The Stage I V8 land Rover also had full time four wheel drive. All subsequent Rover designs were full time 4 WD in order to provide less stress on the rear axles. The 110 retained the Salisbury rear axle it inherited from it's 109 parent through about 1993. Finally the 10 spline axles were replaced by stronger 24 spline axles.

Seriestrek (US) and Great Basin Rovers (US) both offer 24 and larger front and rear axle upgrades for Series Land Rovers. 


Take a system approach, considering the entire drive train working together before buying parts

You always need to think about how your new engine's power gets to the ground and how any changes in weight distribution will affect the suspension and vehicle stability.  It all has to work together as an integrated whole if it is to hold together and provide better than stock performance.  As you design your swap, don't forget that drive train!  Afterthoughts usually end up becoming drive train broken bits. It is usually a good idea to maximize the use of available off the shelf parts and minimize the use of custom adapters and other parts.  A broken custom part may leave you stranded for a long time if it breaks.  When considering an engine, also consider what gearboxes were used with that engine, which gearboxes can be fitted to a Series transfercase using off adapters, how well available gears would work at your driving speeds with available ring and pinion options. Don't forget that Ashcroft transmission makes a high ratio kit that raises the high range rations leaving the low range ratios the same and that Heystee Automotive and Roverdrive both make a robust overdrive that adds a fifth gear to a 4 speed gearbox (Can not be used with high ratio gears). 

88 owners should take special note.  The rear propshaft is quite short.  When the Land Rover factory made any changes that shortened the rear propshaft, such as adding a Salisbury differential or a six cylinder engine, they only made the changes to the 109, never the 88.  When the Land Rover factory added extended shackles as a option to fit taller tyres they only offered them on the 109.  Extended shackles increases the u joint angle. When the Land Rover factory decided to make a 5 speed gearbox standard they lengthened the wheelbase a couple inches and moved the engine forward for additional clearance.  May I suggest that you heed this and not make changes that shorten the 88 rear propshaft without carfull engineering.  A custom high angle U joint propshaft with long slip joint  could only help.  Both Seriestrek and Great Basin Rovers can set you up with 24 spline axles and differential parts to convert your existing Rover axles to 24 spline without shortening your rear propshaft.   Series Land Rover rear axles sit 1-1/2 inches forward of the body rear wheel arch's centre.   You could use a 1-1/2 inch offset plate between the rear axle and rear spring to centre the rear wheels within the wheel arch.  That will give you 1-1/2 inches of additional gearbox, engine or transfercase length without shortening the 88s already very short rear propshaft. If you move the rear axle rearwards without moving the transfercase rearwards you will need a longer rear propshaft.



In the late 1970's and through most of the 1980s, before onboard computers took over most all the emissions functions,  engines were detuned, forced to run in modes that shortened their time between rebuilds and covered in vacuum hoses and vacuum valves.  They tended to be finicky, overheated easily and were unreliable.   People who worked on these engines learned that engines run better and lasted longer without the emissions equipment.  For American owners it is not true for pre 1975 engines and for later computer controlled engines.  Engines without crank case gas recirculation  tend to gum up and wear out in 100,000 miles or less. It is the combination of effective crank case recirculation and hotter engine operating temperatures that allows engines to go 200,000 miles or more between rebuilds.   I am suggesting that you might want to stay away from 1975 through 1986 or slightly newer petrol engines and keep as much of the factory emissions equipment with the engine as possible.   Its good for the engine life expectancy and good for your environment.

In the United States, each state sets its own vehicle emissions standards.  Learn what the requirements of your state are before selecting an engine for a conversion or buying a used vehicle with an engine conversion.  You can easily find yourself with a vehicle that can not be registered in your state.   In California, a vehicle must meet the emissions requirement for the year the vehicle was manufactured OR the year the engine was manufactured, WHICHEVER IS NEWER.   In California vehicles and vehicles with engines newer than 1974 must undergo periodic emission inspections and testing.  If your Series Land Rover and your engine was built before 1975 you are excluded from periodic testing, but don't forget that  crank case recirculation and a 180 degree or higher thermostat helps your engine last longer and run more efficiently.  You can drop a 1975 or newer engine into a 1974 or earlier Series Land Rover and not tell the state that you have converted the engine but you would be in violation of state law.  If you get into an accident, your insurance company might refuse to pay up if they did not know about the conversion when they wrote the policy.  Where you run ito problems is when you sell the vehicle and the state asks to inspect it before granting a license or when you move into a state that requires emissions testing of the engine in your vehicle.  Most states do not require emissions testing on diesel engines made prior to 2000.  I am suggesting that you learn the emission requirements for your state and any state that you are likely to move into before choosing an engine for a conversion and leave the emissions equipment in place and functional on the engine you choose.  Also don't be afraid of 1990's and newer computer controlled engines.   They are quite reliable, often more so than carburetors and points or early electronic ignition systems.  They help your engine run cleaner, produce more power, get better fuel mileage and they are continually retuning your engine to compensate for things like altitude, air temperature, coolant temperature and engine component wear.  And a modern EFI controlled engine runs smoother in high camber rock crawling situations than a carbureted engine.  They are more complicated but they are dependable and have a limp home mode that compensates for a wide range of component failures.  My 1960 Series Land Rover has a 1970 Mustang 302 installed and 1991 Mustang EFI.  It does not require periodic emissions testing but with the EFI, the engine burns way cleaner than either the vehicle or engine did new and it gets better fuel mileage with increased reliability. A win win win situation that just took a little thought up front.


Choosing an engine

The first mistake many people make is in thinking that a small displacement engine will always give better fuel mileage. This is only true if the small engine is in a lightweight, properly geared, aerodynamic vehicle. A small engine in a heavy Series Land Rover with Series Land Rover aerodynamics will often overwork itself, which is completely counter to the engine's efficiency.   A small four cylinder engine may not have the torque and horsepower required to move the Land Rover where the driver wishes to drive or at the speeds the driver wishes to go.  To compensate, the driver tends to run the engine in a higher RPM range, or lug the engine at a lower RPM range with the throttle pedal at or very near the floor.  As a result the vehicle performs poorly and the engine often gives poor fuel mileage.  The larger displacement engines have a greater economy advantage in that they have broader horsepower and torque bands and are more likely to be used within the engine's most efficient operating range. Larger engines carry reserve power that the smart driver can opt to use when they need it, and keep a light foot on the pedal when they do not.  On the other hand if you install an engine that is much larger than your Land Rover needs for the kind of driving you do, the engine will waste fuel producing a power reserve that you may never use. 

The trick is to match engine to the vehicle and driving conditions, including enough reserve power to use when needed but not more than will be needed. The larger the apparent displacement of the engine the more torque it will produce.  Nothing says torque like lots of cubic inches.   The stroke and cylinder bore largely determines the RPM range where that torque will be produced.  A 2.25L engine with a long stroke  and small diameter cylinders will tend to produce its torque towards the low end of the engine's RPM band.  A 2.25L engine with a short stroke and large cylinder diameter will tend to produce its torque at higher engine RPMs.  When considering an engine for suitability in a Series Land Rover being used off road, or comparing engines for suitability, be sure to check to see if the stroke is larger than the bore.  Since long stroke cranks are good for low end torque, adding a stroker crank always helps.

People swapping in engines are often tempted to swap in aftermarket speed equipment.  Please keep in mind that most aftermarket speed equipment adds horsepower to the high RPM areas at the sacrifice of low end power.  Things like long duration cams, larger diameter intake passageways and larger intake valves help at high RPM but hurt at the low end.   Always ask to see the power curve below 3000 RPM and compare it to stock.  Unless the equipment was designed to enhance towing ability, chances are good that stock may be better at providing low RPM power than most speed equipment.   If the manufacturer is not willing to talk about power curves between idle and 3000 RPM, look elsewhere.

As nearly as I have been able to determine, a loaded hard top 109 prefers about 150 HP or more along with a wide low RPM torque curve for the engine to stay mostly within its peak efficiency band during mountain highway driving.  Lighter weight Land Rovers such as 88 or those without a hard top can do well with less power.  Land Rovers that don't spend time on mountain highways at altitude do not need as much power as those who do.  Lighter weight Land Rovers often do well  with the Land Rover tdi engines, the GM "Iron Duke" Fours and the like.  The heavier Land Rovers often do best with 6 or 8 cylinder engines that have broader horsepower and torque bands, which allows the vehicle to perform as needed with the engine in its most efficient operating range.  This usually provides a  greater economy advantage over smaller engines that struggle to perform as required.   

Big Block V8's are a very tight fit in a Series engine bay and can easily overload stock LR suspension options. They require a lot of extra engineering to get right and you tend to end up with a nose heavy rig that may or may not have adequate suspension for front articulation. A big block engine produces more reserve power than you could ever use unless you were towing something very heavy and gets crappy petrol mileage while breaking drive line parts. I personally believe that a big block engine or an engine heavy enough to max out the front axle off road rating of stock LR one ton springs doesn't belong in a series rig. If you decide to go the big block route, a Defender front clip would maximize the space available. There are people who successfully manage to squeeze a 6.2 GM V8 diesel into a Series Land Rover engine bay  and they seem to be getting somewhere in the low 20 something miles per US gallon.

If the conversion you are considering does not produce at least 120 hp below 3000 RPM and a goodly amount of torque below 2200 RPM you might as well stay with a Land Rover four cylinder engine or another brand of four cylinder engine that is an easy swap in front of a Series gearbox.   The difference between that and other engines will likely not be enough to justify the costs and work to make the conversion. A built up 2.5L petrol or 200 tdi would be good choices for a mild increase in power that would be quite noticeable.  Especially in an 88.    Conversely too much horsepower or torque and you just burn more fuel than you  need to and break things. My suggestion is that unless you plan to pull a heavy trailer up steep mountains 150 to 250 HP is a good range to be looking with the lower part of that range maybe more fuel efficient and less apt to break things.  When looking at engine specs, remember a Land Rover is not a streamlined rice rocket. Look at the specs at 3000 RPM and lower.   Engines that put out lots of low end torque tend to prefer to run in the lower RPM range.    Peak torque in the 1700-2200 RPM area is good.  Peak torque much higher than that is or little use for off road work.  For all around off road and highway driving I suggest anchoring your low ratio first gear to around 55:1 at the axle and  your top gear ratio for the best fuel efficiency at 65 MPH.


Consider compatibility of the engine with available gearing
Your gearing should be carefully chosen to keep your engine inside its power band from technical off road work through highway cruise. The standard Series Land Rover low range first gear ratio 40.7:1 at the axle.  High range fourth gear is 5.4:1 at the axle which translates to 65 MPH at 3,682 RPM using 32 inch diameter tyres (stock 109 tyre size).  This is fine for many petrol four cylinder engines but petrol 6 and 8 cylinder engines along with diesel engines usually prefer to lug along in the 2-3000 RPM range where they deliver their best fuel economy.    Torqy V8 engines can handle wider RPM steps between gears so a 4 speed gearbox works well with them.  Diesels with narrow power bands often can take as many gear ratios as you can provide. Drop a V8 ahead of stock Series gearing and you will be able to go slow very quickly.  A 3.54:1 ring and pinion  may get you good highway cruise RPMs at the cost of low range off road gearing unless you plan your ratios carefully.

One thing that seems counter intuitive until you run overall ratio calculations is that the overall gearing ratios of a Series Land Rover with an overdrive  are very similar to those of a coiler Land Rover with five speed manual gearbox.  A Series gearbox plus Roverdrive have very similar ratios as a LT77S.  The combined ratio of the LT230 transfercase high gear and the 3.54 R&P is ball park to that of  a high range Series transfercase gear and the 4.7:1 ring and pinion. 

Here is a comparison chart showing the differences for high range fourth gear  (1:1 ratio) RPMs at 65 MPH with 32 inch diameter tyres mounted. Arranged in descending 4th gear RPM order.

vehicle & gearing

Fourth gear RPM (32" tyres)

Fifth gear or Roverdrive

2.5L Ninety and One Ten

3986 RPM @ 65 MPH

3349 RPM @ 65 MPH

Stock Series Land Rover



V8 Defender with 4.1 ring and pinion



tdi Ninety and One Ten



Series Land Rover with  4.1:1 ring and pinion



V8 Defender



Series Land Rover with 3.54 ring and pinion



Series Land Rover with Ashcroft high ratio kit


No fifth gear or overdrive

These ratios and the fact that the LT77S and 4 cylinder Series bell housing patterns are the same is what makes Land Rover 200 tdi engine swap into a Series Land Rover so attractive.

A Series gearbox has about the same overall strength as a LT77.  The LT77S is stronger than the other two.  A R380 is stronger yet but has a different bell housing pattern. The Series transfercase is stronger than the LT230.  Ashcroft makes an adapter that fits a Series Transfercase to a LT77S gearbox.

Series Land Rover and Salisbury stock ring and pinion sets are 4.7 and 3.54:1 ratios.   Common aftermarket ratios are 4.75:1 (stronger R&P) and 4.1:1. If you need something different you might start looking at Toyota axle assemblies. Some of the Toyota Land Cruisers have the same front and rear axle offset as a Land Rover, as do 1971 and earlier Jeeps that use the  Dana 18 transfer case.  These are both good places to explore alternative drive train components.

From my experience  doing expedition driving through many terrains, including moderate rock crawling I feel the stock Series Land Rover 40.7:1 low range first gear ratio is too high. I have come to think that somewhere around 55:1 is a much more useful low range first gear ratio. If you take a carbureted engine with mechanical linkage much lower than that you will start having a hard time keeping your foot steady enough for a smooth low RPM throttle response. Your top gear should be the RPM where your engine gets its best fuel economy.  You will be limited by available gearing and how well your engine can handle the ratio steps in between first gear and top gear.    For additional information and gear ratio numbers I have three web pages for your reference:

There are three basic combinations of gearbox and transfer case that you can use:

  •  Land Rover engine, gearbox and transfercase combination that was supplied by the factory
  • This would be your easiest solution.  The custom bits are likely to be engine mounts, exhaust, transfercase cross member and propshafts.  You would need to make the front axles and transfercase compatible for either full time 4WD or part time 4WD.  A 200tdi into a Series Land Rover is almost a straight bolt in conversion to a Series gearbox and uses off the shelf parts. Series Land Rover manual gearboxes are too weak to put behind the Rover V8s and expect long term reliability.  Ashcroft transmissions Ltd. (UK) has an adapter that allows a Land Rover five speed gearbox to fit to a Series Land Rover transfercase.

  •  Non-Land Rover engine with Land Rover gearbox

    The manual gearboxes used by Land Rover are not very robust and often do not hold up well with the stock Land Rover engine when used hard.  Unless you plan to install you gearbox with wing nuts it is a good idea to be conservative with the power you place in front of them.   This means the engine in front of a Series gearbox or LT77 should be about 120 HP, 160lbft  or less. The LT85,  LT95 and LT77S are best off with an engine under 180HP and 200lbft of torque.  The  RD380 should probably be used with an engine producing less than 200hp and 250lbft of torque.  A few companies make adaptors for this combination.  Most reside either in the UK or Australia.

  •  American light truck engine and American top loader gearbox.
  • These combinations can be a lot more powerful and a lot more robust than using Land Rover engines and gearboxes.  Frequently you can find off the shelf parts to mate the engine, clutch, gearbox and Series transfercase together.    This greatly simplifies the conversion engineering and makes later maintenance easier and quicker.

Some companies that manufacture and sell adapters:

Advanced Adapters (US)
They have a wide verity of adaptors but a very awkwardly organized web site. It may take an effort to find what you are looking for since they do not support Land Rovers. They have off the shelf adapters to mate common American top loader gearboxes to the Series transfercase.

Ashcroft transmissions Ltd. (UK)
High ratio gear conversions for Series transfercases, Overdrive for LT230 transfercase, adaptor that allows a Land Rover five speed gearbox to fit to a Series Land Rover transfercase and more.

Dellow Automotive (Australia)
Adapters to fit Toyota B - 2B or 3B diesel engines to Series gearboxes.  Also adapters to mate small block Chevy and Ford V8s to  Land Cruiser gearboxes (stronger than a Series gearbox but not as stong as the American light truck gearboxes)

Marks 4wd Adapters (Australia)
They mostly have adapters for Japanese engines that are not available in the US market. They do have adapter kits to fit GM V8s into Range Rovers. If you are using Land Cruiser drive train components it is worth checking over their site.

Motor & Diesel Engineering (UK)
Mostly adaptors for diesel engines not available in the US except by special import.

Novak Adaptors (US)
Their specialty is Jeep power train conversions using American engines, gearboxes and Transfer cases Of interest to Land Rover owners are adaptors for the Dana 18 transfer case They also have a GM bell housing to T18 & 19 gearbox adaptor. They have a good, well organized web site.

Seriestrek (US)
Has a Mercedes 616/617 4 cylinder diesel engine to Series gearbox adaptor. The 616 engine is a little anemic for a 109 but worth looking into for an 88 if you want to try used cooking oil as a fuel.


Consider how the engine weight affects the front axle weight and suspension
A 2.25L Land Rover petrol engine weighs about 450 lbs.  The Land Rover six cylinder engine weighs a little over 600 pounds, but sits back farther so the front axle weight is actually lower than a four cylinder. Here are some factory specs for Land Rover Series III front axle weights:

Factory front axle specifications

88 regular

88 regular

88 station wagon

109 regular
2.25L petrol

109 regular
2.25L diesel

109 station wagon
2.6 petrol

109 one ton

Unleaden front axle weight

1640 lbs.







Maximum cross country axle weight








Land Rover factory specs assume that about 80 to 85% of weight added to a series Land Rover (driver, passengers, fuel, gear) will be carried by the rear springs.  One ton front springs are the heaviest duty springs you can put under a Series Land Rover.  I suggest that one of the first steps someone contemplating an engine swap should do is load their Land Rover up as it would be beginning a long off road trip and taking it to the public scales for a weighing.  The weight of just your front axles on the scale minus the approximate weight of your stock Series Land Rover engine will help you calculate the maximum engine weight your vehicle can support off road. And don't forget some of the weight of a heavier gearbox will supported by the front axle as well.  And if you don't have a winch you may want to keep at least 200 pounds below maximum spring weight in case you wish to add a winch in the future.


Knowing your engine's air flow under your normal operating conditions can help you figure out such things as air filter and pre filter sizes and matching petrol engines to carburetors.  Here is an interesting formula I keep seeing for making the calculations that can be a real eye opener.

Some low RPM calculations for petrol V8s

Engine CID

302 Cubic inches




2000 RPM

131 CFM














What's interesting is how little air these engine pump at low off road revs. The large carbs sold at performance places feed those near redline power runs and over carb most if not all normal driving and off road use.  A 500 cfm four barrel carburetor is all most people need with a V8 in a Land Rover and would be an economical choice.


Thoughts about petrol V8 engine conversions

Thoughts about diesel conversions


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