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[Peter Holden]

You make an interesting comment but I though we were comparing 2.25 engines not adding in the 2.5.

As I have said before, we have 2 S2s both with 2.25 diesels, one a 3 bearing and the other a 5.  I doubt you would be able to tell the difference between them if you didn't know what was under the bonnet

Peter

[Alan Drover]

I agree about the 17H. I've had mine for some time now and it is in my opinion the best of the petrol engines.

[gilbo]

Well if, as stated the '3MB 2.25 con-rods are too long' then so are the ones on the beloved 17H. They are exactly the same length.
I have no experience of the diesel engines (2.25 or 2.5) but suspect the same would be true of the con-rods in those?

[Peter Holden]

I would presume so since you can use the diesel rods in a petrol engine and the replacement petrol and diesel cranks are identicl and carry the diesel engine part number

Peter

[PetrolFour]

Well if, as stated the '3MB 2.25 con-rods are too long' then so are the ones on the beloved 17H. They are exactly the same length.
I have no experience of the diesel engines (2.25 or 2.5) but suspect the same would be true of the con-rods in those?

Do you know, I think you're correct. Now I think of it, and  the diesel's geometry is unlikely to differ, the gudgeon-pin centre moves nearer the crown. In which case, scrub my comment. Con-rods 2.25/2.5 same length. Sorry.

I was mixed in my head with Ford engines, a plodder is usually short con-rod / long stroke. A race-engine, short-stroke, over-square/ long con-rod. Again apologies.

Nonetheless, I stand by the essential point 5MB 2.25 or 2.5 is smoother, and with a few tweaks delivers in 2.5/2.8 form to my mind the very best petrol. And they're all a compromise, this being the best compromise. It's the foundation of the 200TDi. The 200TDi is not 3MB, and doubtful it could be.

[PetrolFour]

I should have written thus:

==========
Rather than simply another 250cc over the 2.25 3MB, much of the extra torque/power/ ecomony comes via its better cylinder head/ manifold/ cam/ carb/ improved geometry long-stroke design.

==========

Geometry alters power characteristics. And none of makes a 3MB bad.

[Wittsend]

An interesting and somewhat pointless debate. Nothing you say can make either version of the engine bad.

On a scale of 0 to 100 (100 being absolutely brilliant and reliable)

You/we are arguing over whether 3mb engines are at 97 or 98 

(Nothing will be 100% perfect.)

I'm not sure what any of this proves



 

[LN11AAB498A]

A question from someone trying to reconcile what I`ve read here with the following statement. I accept that in this kind of debate our own experiences, likes & dislikes are all very subjective.

In his statement, Richard Hall (Glencoyne Engineering) refers to both diesel & petrol engines, how can it be so at odds with some of the comments above?

2286cc petrol/diesel, overhead valve, 5 bearing crank:  In 1980, Land Rover finally did something about the crank failures which had plagued its four cylinder engines for 22 years.  The new crank was so strong that Land Rover could (and did) get away with using the same crank for petrol and diesel engines.  These engines lasted beyond the end of Series III production and into the first couple of years of the new Ninety and One Ten ranges.  Well worth paying extra for, if you are looking to replace a worn or broken 3 bearing engine in a Series vehicle. Crankshaft rear oil seal design is also far superior to the 3 bearing and easier to replace if it does leak.

[PetrolFour]

It'll be about context. RH writes as LR saw things in the context of the time, whereas today's owner is a whole lot less likely to treat something he owns in the way a certain GPO employee dearest to my heart treated his 'issue' 109 back then. Margins are tight. You don't need too many crank-failures for it not to be worth sorting, both for reputation and profit. Can you imagine the admin cost alone?

And today's 3MB owner has no thought to paying for warranty claims, competing in the market etc etc. He need not think. "I've had mine for 40 years and I've never a crank go etc etc" Thus with an owner mindset, limited miles, no danger of the dealer network in ours ears, and no bill. A 3MB is fine. In fact, very good.

Thus from this view, what advantage the 5MB? None. No need.

There's several standpoints here. Each correct from where they sit.

[LN11AAB498A]

It'll be about context. RH writes as LR saw things in the context of the time..
.."I've had mine for 40 years and I've never a crank go etc etc" ...
Thus from this view, what advantage the 5MB? None. No need.

Forgive me, but I am none the wiser. That doesn't deal with RHs engineering opinion.

I started my post accepting that these views are generally subjective, so the fact you have had yours for 40 years without a crank going doesn't really deal with the question. I was really hoping for views that are more objective, evidenced by engineering knowledge.

He clearly believes the 3mb is weaker that the 5mb, giving it significant advantages over the former.

You say "RH writes as LR saw things", that isn't how I read it at all. I don't know what you mean about context either, Glencoyne Engineering is a modern day engineering company & RH is relating his opinion in the modern day, that is the only context that matters.

RH believes "the 5mb crank was so strong it was kept through to the Ninety and One Ten", & "Crankshaft rear oil seal design is also far superior to the 3 bearing and easier to replace if it does leak". Whereas you say "what advantage the 5MB? None". But surely, if the 5mb is stronger, and you had to replace a broken 3mb engine why wouldn't you fit the 5mb if you could?

RH has not said the 3mb is a bad engine, he`s just making a comparison of the two.

[PetrolFour]

2286cc petrol/diesel, overhead valve, 5 bearing crank:  In 1980, Land Rover finally did something about the crank failures which had plagued its four cylinder engines for 22 years.  The new crank was so strong that Land Rover could (and did) get away with using the same crank for petrol and diesel engines.  These engines lasted beyond the end of Series III production and into the first couple of years of the new Ninety and One Ten ranges. 


Well worth paying extra for, if you are looking to replace a worn or broken 3 bearing engine in a Series vehicle. Crankshaft rear oil seal design is also far superior to the 3 bearing and easier to replace if it does leak.

RH's first paragraph speaks of the development path done in 1980, why this was done, and the result of the improvements. LR found the resulting crank stronger etc etc. These results came to form the future model line-up in  that era.  That'd be what LR did,  conclusions they came to, and how these improvements were used.  No opinion from RH. This is not RH's opinion, yours or mine. Purely an account of development, why it was done, and outcome within LR.

In the second paragraph, RH then  expresses his opinion. Such developments are "Well worth paying extra for". Most would see it reasonable to agree. Thus, given choice, we'd take the 5MB. However the "I've had my 3MB for 40 years and I've never a crank go etc etc" set won't see the need.

Here's pix of the improved oil-seal RH considers "far superior". Here it's sitting in a modded clutch-housing to allow this seal easy use in a series. I can show, perhaps with another improvement over  the 3MB, the 5MB's  inertia-starter. 

However, it just as likely, the "I've had my 3MB for 40 years and I've never a crank go etc etc" set will not see the need for this either. No need for 5MB. A 3MB is as good? And from their standpoint, they would be correct.

This becomes circular logic from hereon in...

[2286]

I personally found the 5 bearing crank engine quitter than the 3, having had both in a 2B FC,. Also had a very early 5 bearing  crank diesel S3, the first in local LR dealer & the staff there remarked on the fact it was quieter , and subsequently found that was one of the reasons it was modified  to achieve some of the new drive by noise regulations.

I drove a 5mb petrol and i could not hear if it was running or not, being used to a heavy oil 3mb.

[Peter Holden]

Drive a series 1 with the spreadbore engine or a 6 cylinder S2A or S3, they are so quiet thhat if you stand next to them at tickover you cannot hear them

Peter