3.9 Bottom end

Jackstar · Feb 23, 2021

Hi all, I've looking to replace my big end and main shells on my 3.9 and I'm sure that the con rod bolts needs replacing is it the same case for the mains bolts?

Also there seems to be two types of con rod fixings, bolt or studs and nuts, do the stud and nut version also need replacing?
Im yet to strip mine down to see what type I've got

discool · Feb 25, 2021

Jackstar said:
Hi all, I've looking to replace my big end and main shells on my 3.9 and I'm sure that the con rod bolts needs replacing is it the same case for the mains bolts?

Also there seems to be two types of con rod fixings, bolt or studs and nuts, do the stud and nut version also need replacing?
Im yet to strip mine down to see what type I've got

A workshop manual will state if the bolts require replacing.
All of the disco 1 V8s con rod caps are retained by nuts and bolts, 602061& 602609 .The 3.5 ranges just had a bolt only AUU2038L
I don't have any info on the 3.9 RR, as I went for the 3.9 disco

Jackstar · Feb 25, 2021

I should have said mine is a 1996 disco.
So I'll need to replace the nuts and studs, I'll look for the torque sequence for these.

Where's best to get the fixing from for the con rods and mains?

Thanks

discool · Feb 25, 2021

The torque setting for big end bearing bolts is 51Nm or 38 lbf ft
The bolt part no. 602609 is not for serp belted engines ie up to 1994 only according to island, but Rimmer’s state whats in my parts catalogue thats just the one bolt.
So could be another part no. to find if you have a serpentine engine.
https://www.island-4x4.co.uk/bolt-7094-602609-p-15582.html
https://www.island-4x4.co.uk/special-602061-p-15578.html
https://rimmerbros.com/Item--i-602609
https://rimmerbros.com/images/pdfs/discovery.pdf

Henry_b · Feb 25, 2021

You should be good.

No need to replace them unless they snap, or the threads are damaged "for whatever reason"..

Jackstar · Mar 1, 2021

I'm having 2nd thoughts on it being rod bearings now, I've got a knocking noise when the engine is up to temp,sounds worse when under the car than from above it also sounds sweet from cold, the knocking goes at 3000rpm and above, and the coolant overflow bottle is overflowing.

Am I right in thinking these are all symptoms of a slipping liner?

v8250 · Mar 12, 2021

Slipping liner? Yes, they can sound like this. Might be worth having chat with Richard at Turner Engineering re' fault diagnosis + the correct components for the 3.9 RR engine, though there's nothing complex with the rebuild. Do you have an engineer's stethoscope? They are superb at accurately pinning down the location of a fault and you should be able to listen to which cylinder/s the noise is coming from.

Jackstar · Mar 12, 2021

I've brought a good condition block to fit my heads to, I'll strip and a fault find the original block later, probably rebuild if it's useable.

3.9 Bottom end

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