RV8 big end cap bolt torque

[debaron]

What do you Rover V8 builders set your to?

Manual says 20nm + 80 degs but that only equates to around 70nm on my wrench (Snap-On Techangle)

Engine is stage III 4.6 with uprated compression (195 psi) - around 310 bhp

Cheers

[paintman]

There are quite a few different figures given over the years for the various incarnations of this engine, both torque and torque plus angle - as a google will show you.
However, the LR manual for the 4.0 & 4.6 gives the figures you state so I would go with those.
FWIW I take the view that angle tightening often involves stretch bolts so probably an idea to replace them (although they aren't so marked in the manual)& then tighten to the figures you give - assuming you are using standard rods. Overtightening is likely to weaken the fastener & could result in failure in service.
Unless you're using special con rods in which case I would ask the supplier.

[Pumaracing]

Why do you say "only"? Just how much torque do you think a bolt that size ought to be able to take?

Anyway those are the right settings and the bolts are reusable. Just because an angle tightening method is used doesn't automatically mean that the bolt is being taken past its yield point into non-elastic stretch.

Edited by Pumaracing on Sunday 9th March 17:19

[Sardonicus]

70nm is not low in my estimations for that size fasteners i would have said 55-60 nm so if that figure is what you found already mentioned but not all angled torqued bolts studs are throw away

[debaron]

paintman said:

FWIW I take the view that angle tightening often involves stretch bolts so probably an idea to replace them (although they aren't so marked in the manual)

I got the rebuild parts (main and big end shells plus big end cap bolts) from a well known RV8 engineering company who stated that the bolts are categorically not reusable - but then I suppose they would as they are selling them!

[debaron]

Pumaracing said:

Why do you say "only"? Just how much torque do you think a bolt that size ought to be able to take?

Anyway those are the right settings and the bolts are reusable. Just because an angle tightening method is used doesn't automatically mean that the bolt is being taken past its yield point into non-elastic stretch.

Edited by Pumaracing on Sunday 9th March 17:19

I ask because when removing them they took about 90 nm to undo but only 70 on retightening (using same bolt) but I suppose thats the stretch part coming into play?

I was only checking wear on big end bearings so when reassembling in final build I will be using new stretch bolts - which may well yield 90 nm final torque.

[Sardonicus]

debaron said:

I got the rebuild parts (main and big end shells plus big end cap bolts) from a well known RV8 engineering company who stated that the bolts are categorically not reusable - but then I suppose they would as they are selling them!

For the cost involved and the fact they are rod bolts probably not a bad thing belt & braces and all that ...............

[debaron]

Sardonicus said:

or the cost involved and the fact they are rod bolts probably not a bad thing belt & braces and all that ...............

You're quite right Simon - Don't spoil the ship etc etc.

Although at £45 plus VAT they were more expensive than the big end shells and mains put together!!

[Sardonicus]

debaron said:

You're quite right Simon - Don't spoil the ship etc etc.

Although at £45 plus VAT they were more expensive than the big end shells and mains put together!!

Really what quality bearings did you get? hope they are not white box specials you really need quality copper/lead bearings for a proper build