M51 and M57 block swap? P38

[Blanco]

An article /letter from LRO suggests that a knackered M51 can be relaced with a secondhand M57,  in a P38 provided that the fuel pump and original ancilliaries are transferred. Its an intriguing prospect. Over on the BMW engine Land Rover FB site they don't give the idea much credence, and I know the displacement of the engine is very different but it I just wondered what are the hard facts of why it couldn't work??

Edited October 3, 2018 by Blanco
Accidental copy and paste first attempt

[smallfry]

Engine mount brackets are different...…. mounting bolts a different pattern. For a start. 

Inlet manifold will not fit. Don't know if the cylinder head could be swapped, but why would you ? It a two valve per cylinder head, and the M57 is four, but I guess you are talking about fitting the M57 head onto the M51 ? Pistons look different too. 

Same bellhousing bolt pattern though, and I believe the crankshaft bolt pattern is the same too 

 

[Blanco]

Engine and head together, just keep the outer bits.  The manifold(s) if necessary, .... the big issue seems to me to be how flexible the adaptable fueling function of the ECU is (ie the DDE 2,3,4, etc) If the brain  coped then it might just work and you could gain the extra torque of the long stroke crank and larger displacement without the headache of a brain transplant . It just seems to me that the wiring side of these things is the real headache to ornery oily fingers and that its  one I would try unless somebody can say why not???

[David Sparkes]

17 hours ago, smallfry said:

... Inlet manifold will not fit. ...

Do not overlook the fact that the 2.5 6 cylinder had two variations of inlet manifold, with different stud placings, so the heads must have changed as well.

The early manifolds were aluminium, soaking up the high under-bonnet temperatures and pre-heating the incoming air.
The later ones were black 'plastic' (carbon fibre?) which were less efficient at conducting heat.

Thus it's possible that the later one will fit the 3.0 engine, whereas the early one won't.

Regards.

[smallfry]

The M57 has two inlet ports per cylinder, and the M51 only has one.

So the M57 manifold has 12 outlets, and the M51 has 6

As I said, I do not know if the cylinder head COULD be swapped, but you would still be limited to 2.5 litres, as the 3.0 M57 has a bigger bore AND a longer stroke. So even if it were possible to swap the crank, you then would have the problem of a conrod and piston combo that would suit the smaller bore, and still NOT be 3.0 litre.

Then of course, you would have to find an injector that would fit the head. Either that or go the whole hog and fit the M57 common rail system

All in all, just fit an M57. It will be a lot easier, but not cheap, and probably more satisfactory. Although I have to say that the good old fashioned fuel injection system is much more reliable and dependable.

I am still ponderering whether to fit an M57 to my V8 90 in place of the petrol engine.  

[RedLineMike]

fitting the m57 is cheaper than other swaps out there, you can get the majority of the parts for the conversion for less than a grand if you buy a complete car

[Quagmire]

15 hours ago, smallfry said:

The M57 has two inlet ports per cylinder, and the M51 only has one.

So the M57 manifold has 12 outlets, and the M51 has 6

As I said, I do not know if the cylinder head COULD be swapped, but you would still be limited to 2.5 litres, as the 3.0 M57 has a bigger bore AND a longer stroke. So even if it were possible to swap the crank, you then would have the problem of a conrod and piston combo that would suit the smaller bore, and still NOT be 3.0 litre.

Then of course, you would have to find an injector that would fit the head. Either that or go the whole hog and fit the M57 common rail system

All in all, just fit an M57. It will be a lot easier, but not cheap, and probably more satisfactory. Although I have to say that the good old fashioned fuel injection system is much more reliable and dependable.

I am still ponderering whether to fit an M57 to my V8 90 in place of the petrol engine.  

I thought the OP was talking about swapping the entire engine, and then fitting the original ancillaries? 

 

 

[Blanco]

He was, this is the article Here, ...........  just sounds so much easier than the whole loom headache, ...... probably too good to be true.

[smallfry]

9 hours ago, Quagmire said:

I thought the OP was talking about swapping the entire engine, and then fitting the original ancillaries? 

 

 

He was, but what ancillaries ? Whoever wrote that article in LRO clearly has no idea what he is talking about.