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Series Engine Numbers - 3 Or 5 Bearing

Series Engine Numbers - 3 Or 5 Bearing

Quite often we hear the question asked whether a vehicle is fitted with a 3 main bearing engine, or a 5 main bearing engine, and how can you tell which is which?

A simple way of ascertaining whether you have a 3 or 5 bearing engine is to look at the castings on the block. There are extra ‘webs’ cast into the block on 5 bearing engines, to strengthen the unit. Below you will see two photographs, the top one of which is a 3 bearing engine, and is painted a duck egg blue colour.

petrol2_25_1.jpg

You can see the engine number on the block quite clearly in the above picture.

The second photograph shows a 5 bearing engine, and again you can see the engine number quite clearly, and it is pretty easy to see that it is a terracotta red colour!

petrol2_25_a1.jpg

It is also very easy to see the extra webs in the casting of the block.

Now, a bit more about engine numbers…

There has been a range of engine numbers supplied to the 2.25 litre engines we have fitted in our Landies.

Numbers commencing with 151 are early SII 2.25, 3 Main Bearing engines.

Series IIa 1968-71, numbers commencing with 271 suffix A –J are 2.25, 3 main bearing diesel engines, as are 276 suffix A – J and 271 suffix K onwards.

Numbers commencing 237 and 252 are 3 main bearing 2.25 petrol engines, of 7:1 compression ratio.

The engines fitted to SIII’s are numbered as follows. (Commencing with the first 3 numbers)

901…….3 main bearing, Petrol, 8:1 compression
902…….3 main bearing, Petrol, 8:1 compression
904…….3 main bearing, Petrol, 7:1 compression
906…….suffix A – J, 3 main bearing, Diesel
951…….3 main bearing, Petrol, 8:1, military specification
952…….3 main bearing, Petrol, 7:1, military specification


From 1982 onwards Land rover started using the 5 main bearing engines in their vehicles, and in fact some of the petrol engines were carried over into the early 90’s and 110’s.

361……5 main bearing, Petrol, 8:1 (36123672B onwards metric)
364……5 main bearing, Petrol, 7:1 (36407286B onwards metric)
365……5 main bearing, Petrol, 8:1, military specification
And last, but by no means least,
366……5 main bearing, Diesel (36619420B onwards metric)
369 Odd one this. Seen a few now... According to Turner engineering this is a 2.25 5 BRG diesel, probably fitted to a London taxi (Hackney carriage) which used to use the old BMC diesels. An upgrade for a taxi...

The engines that were carried over to the 90’s and 110’s have serial numbers beginning with 11H and are not exactly the same as the Series engines…they have different front covers, manifolds, carburettors and distributors, to name but a few differences.

Sometimes too, we hear the question, ‘How do I know what compression ratio my engine is?’ Again, a look at the engine numbers will tell you, but if for some reason the number is obscured, then you will find the number cast into the cylinder head, as in the photos below. The top one is an overall view and the bottom one a close up of the stamped mark on the head, highlighted in red. It is important to note however, that this is not always the case…sometimes the compression ratio wasn’t stamped on at all!

8to1a.jpg

8to1b.jpg

It is also worth noting at this point that none of the 2.25 petrol engines described here were ever designed to be run on unleaded petrol. So, to do so, you would either need to obtain and fit an unleaded head, or run using an additive designed to replace the missing lead in the fuel.

Many thanks indeed to Frida, of Turner Engineering for the invaluable assistance with the numbers, and also for supplying Photograph’s of the two types of block. Thanks too, to forum member sf<>< for the images showing the 8:1 compression stamp on the cylinder head.

Turner Engineering’s website can be found at http://www.turner-engineering.co.uk/ . It is well worth a look, especially the section dealing with the reconditioning process.

For further reference, here's another photo of a 5brg engine (mine)

Screenshot_20210505-142739.png


Excuse the share, fave, delete buttons on the image! 😁
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