ARP Nuts on Cooper S Main Bearing Caps

[camshaft2]

Hi,

I have just bought the upgraded ARP nuts for the main bearing caps on my Mk3 Cooper S engine rebuild. The intention was to use the original studs, just replace the original nuts with the ARP ones.

Has anyone had any experience of fitting these with regard to correct torque wrench setting (or is it the same torque as the standard nuts?), the use of loctite on the threads or maybe the ARP thread lubricant?

Also, I noticed that the ARP kit comes with studs, flat washers and the nuts (plus a thread lubricant). Do I need to use washers with my new nuts if using the original factory studs or just use the uprated ARP nut as a direct replacement for the factory nut?

All help gratefully received, thanks.

Paul

[Chalkie]

Should of brought the ARP studs aswell as the old ones will be streched a bit

If a jobs worth doing its worth doing properly or not at all.

I got taught that with engine building

[Vegard]

ALWAYS use hardened washers under the nuts or bolt heads. These always dig into the main caps if you don't. I've bought washers from ARP that I use on every build even with the stock bolts.

[camshaft2]

Thanks Vegard, I will look into the hardened washers from ARP although may just buy the full kit from ARP instead.

[Spider]

As the other guys have more or less said, no point in replacing the nuts only. Just thinking about that actually, I have to say I have never seen a nut fail (not saying they wouldn't) but I've seen plenty of studs and bolts let go.

Also, make sure the spot facings (the machined face that the nut contacts on the bearing cap) is flat and clean and not gouged out. Very important and often overlooked.

[camshaft2]

ARP main bearing stud kit and big end kit ordered from Swiftune today. Also ordered an SW5 cam kit........