Land Rover Series 1 2.25L Engine Conversion

My 1955 Land Rover Series 1 107 was originally fitted with the 2.0l overhead valve side exhaust engine between 1955-1958. This was a 4cyl engine with 39kw and 137 Nm torque. Although the original engine was in the vehicle when we found it we subsequently sold the engine. In hindsight now it’s a pity that we sold it but at the time it wasn’t my intention to do a Series 1 2.25l engine conversion. I always wanted to fit a later 2.25l 4cyl petrol engine that I was more familiar with and was in use for 26 years from 1958 up to 1984. I wanted a more usable engine that would be easier and cheaper to maintain. The earlier engines although original have less power and spares availability is very low and expensive.

Land /rover Engine Conversions

Being a Land Rover engine I thought that it would be really easy to do the engine conversion. But I should have known better. Conversions by their very nature are going to be complicated. Sure you get less complicated and more complicated conversions but in the end its still a conversion. Also this is a very common conversion that is done in series 1 Land Rovers. But despite that there is very little available information about this conversion.

You have to find all the bits and pieces of information and try and piece everything together. Also there are short cuts and easier ways to get this done. Knowing which original Land Rover parts can be used instead of making your own can make the job much neater and more original. So I decided to put all this info into one video. This is not the definitive guide on this conversion as it is merely my experience but it should give you a good idea of what is involved. So at least you can know what you are in for and prepare adequately up front to make the process better.

Firstly lets look at why this conversion makes so much sense

  1. The 2.25L engine is the closest engine to the Series 1 as it was introduced with the introduction of the Series 2 in 1958. So it still retains some level of authenticity
  2. These engines are very common, reliable, long lasting, easy to maintain and more powerful than the 2L

Land Rover Series 1 2l to 2.25l engine conversion

As much as these engines are so close in period and look similar at a glance they are a bit different. The main difference seems obvious but can be overlooked and it is the size. This 2.25l engine is ever so slightly taller and longer than the 2l. Looking closer the carburettor and distributor sit on opposite sides. Also the 2l exhaust comes out sideways to the left while the 2.25l engine exhaust goes downwards.

There are 8 main points to consider on the Land Rover Series 1 engine conversion and they are

  1. Change the bell housing on gearbox to a 4cyl bolt pattern
  2. Change the right hand side engine mounting to use the original 2L or 2.6l engine part number 239449
  3. Change the radiator to series 2a or 3 radiator and make brackets to fit it to the front panel.
  4. Change the air filter battery bracket to a series 2 or series 3 type
  5. Trim the carb adapter and the steel elbow to fit under the bonnet
  6. Change accelerator linkage to a series 2 type with down pull for Zenith/Webber and up pull for Solex
  7. Fit a Series 2 109 exhaust
  8. Plumb new fuel lines to use the 2.25l mechanical pump.

Now lets have a look at all of those in detail to see exactly what I did.

1.   Gearbox and Bellhousing

The series Land Rover gearboxes are mostly interchangeable. I used the original gearbox which is a bit weaker than the later series 2A gearbox but is still compatible. I wanted to maintain more originality so retained the original gearbox.

6cyl bell housing fits 1.6, 2L and 2.6L engines (the 4cyl bellhousing does not have the hole in the starter motor bulge)

Fitting the original gearbox to the 2.25L engine requires a change to the bell housing. Series Land Rovers only had 2 different types of bellhousing. The early OHV (over head valve) 1.6L & 2L and later 6 cyl 2.6L engines use the same bellhousing. Then all the later 4cyl 2.25L engines use a different bellhousing. There is a  difference in the depth and the bolt pattern. The 4cyl bellhousing has a bolt hole in the middle at the top in line with the gear lever. While the 6cyl only has one on either side. The 6 cyl also has a hole in the starter motor housing bulge.

2.   Engine Mountings

Engine mounting points on the block are common as well as the depth from the mounting points to the rear of the block. But what differs are the angle of the mounting bracket to the chassis. On the 107 chassis, the left hand mounting bracket is identical and fits perfectly. However the right hand side mounting bracket needs to be changed. The angle of the original 2.25L engine mount is too steep and results in the engine mount being distorted.

RHS engine mount is incorrect causing distortion of engine mount rubber

So you need to use the original RHS mounting bracket from the 2L engine. This mounting is the same as that used on the later 2.6L 6cyl engine with part number 239449. So these mountings are still available if you don’t have the original from the 2L engine. If you don’t use this mounting you are going to have to cut and weld metal to make it fit and you want to avoid that.

3.   Radiator

It is advisable to use a later series 2 or series 3 radiator for the 2.25l engine. If you don’t do this you may have less efficient cooling and will have to move the radiator forward. Because the 2.25L engine is longer, the space on the 86”/107” chassis is too short. I have used the series 3 radiator which is thinner but taller. This allowed just enough space between the fan blades and the radiator. It is close but should workout.

The series 3 radiator fittings to the front panel are also different. So it won’t just bolt onto the front panel. You will either have to bend the inside surfaces of the front panel or you need to manufacture two right angle brackets for the verticals and a flat bracket for the top mounting. I decided to use the brackets so that I didn’t need to bend and alter the front radiator panel.

Take note the series 3 radiator is taller so you can’t just fit it flush with the front panel as I discovered. You will need to drop the radiator about 25mm lower. This will allow the radiator cap to sit below the front panel and clear the bonnet.

I also put in additional brackets to hold the radiator up as my front panel is aluminium. These aluminium front panels are weaker than the later steel ones. This panel is all that holds the radiator and the wings up. This load can be too much for the aluminium and results in it breaking eventually. So by supporting the radiator on the chassis I have strengthened this front panel. I was able to use the winch mounting holes in the cross member to fit the brackets.

4.   Air Filter and Battery Bracket

The Series 1 air filter for the 2l engine is shorter(lower) than the 2.25l version and it has a smaller diameter opening. So you will need to use the air filter from the 2.25l engine as it has a higher air flow capacity which is better for the bigger engine.

The bracket at front is from a Series 1 and one at back is from a Series 2.

But the Series 1 bracket that it fits onto sits higher on the Series 1 chassis. So you also need to get a Series 2 bracket which sits lower and allows the taller air filter to fit in under the bonnet. These two brackets are interchangeable so you can swop them easily using the same four mounting bolts onto the chassis.

5.   Carburettor height

If you use the normal 2.25l carburettor setup then once you have the air filter pipe fitted it sits too high and the bonnet won’t close properly. So you need to reduce the height of the whole assembly.

This can be done by trimming the carb adaptor that sits between the carb and manifold. The original adapter can be trimmed by machining of 2-3mm. You also have to trim the steel elbow that connects the air filter pipe to the carburettor by leaving just enough so that you can still attach the elbow to the carb with the rubber adapter.

Just note that there are two sizes of elbows. A narrower version for Webber and Zenith carbs and a wider version for Solex carbs. If you can’t get the right size for your carb then you can also use a reducer to adapt them to each other.

6.   Accelerator linkage

The accelerator linkage is completely different because the carburettor sits on the opposite side of the engine. It is possible to use some of the original parts. But you will need to get most of the Series 2 parts including the cross shaft for the accelerator. These parts are fairly simple and easy to get.

The more complicated part is the carburettor linkage. The bracket is the same but the “carburettor bell crank assembly” as it is called is different. There are two types, one that pulls down and another that pulls up. You need to make sure that you have the right one for your carburettor type. The earlier Solex pulls up while the later Webber and Zennith pull down.

The main difference between the two is the spring direction. If you try to use the wrong one you will find that the spring is working in the wrong direction and deforms and doesn’t work properly.

7.   Exhaust

The original 2l engine in the Series 1 has a side exhaust that comes out the left hand side of the engine through the left wing. The 2.25l has an exhaust outlet that goes down in between the chassis rails. So it is not possible to use the original exhaust configuration. Instead, you can use the Series 2 109 exhaust for a 107” or 109” or the 88” exhaust for an 86” or 88” Series 1.

First I tried the SWB downpipe but it is not compatible with the intermediate pipe in that the angles don’t work out and it doesn’t fit properly. You need to use the downpipe for the series 2 LWB.

This downpipe comes out underneath the chassis to the left hand side in a similar way to that of the original downpipe for the Series 1. I found the clearance between the downpipe and the inside shackle plate and bolt to be very close but it appears to just fit.

The part numbers that I used for my 107 were 517632 for the downpipe, 276141 for the intermediate pipe and 562731 for the tail pipe. I also bought a very handy series exhaust fitting kit from Britpart (DA1293) that has all of the necessary bolts, nuts, bracket and rubbers for fitting the entire exhaust.

8.   Fuel lines

The fuel lines is a minor change but they will need to be adapted. The supply pipe from the fuel tank to the mechanical pump and the pipe from the pump to the carb will be needed. Here again the pipe from a Series 2 will fit or new ones can be made up with the correct fittings.

Watch the full video below on my Land Rover Series 1 Restoration at my Youtube channel @theoverlandlegend

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