ARP Bolts.

[App K]

Sure one of you guys will know the big end torque setting for ARP 2000 big end bolts 5/16 on an s rod.

Lots of conflicting information including their own website; 28 lb sounds low to me?

[carbon]

28lbft sounds about right for high spec 5/16 inch bolt (lubricated threads).

But curious why use a 5/16 bolt when the original S rod bolts are 3/8 inch?

[Spider]

55 ft / lb with ARP Lube

[App K]

Ha..thats exactly my point.
Is it 28 or 55/lb.
you could say it might make a difference.

SC rods by the way, that’s why 5/16

[Spider]

SC rods by the way, that’s why 5/16

Ah, OK. In that case - and even ARP will give this advice - contact SC.

[251 ENG]

55 lbs/ ft is for 3/8" cooper s bolts

[App K]

55 lbs/ ft is for 3/8" cooper s bolts

Simon are you saying that you think it is 28ft / lbs?

[Hipwell]

It all depends on rod manufacturer.

I think I did an Aston engine with 5/16" bolts and it was 26ft.lbs. So 28ftlbs sounds pretty good.

They will snap at 55ftlbs, thats a common value for ARP 2000 3/8" bolts. Arrow suggest 43-45 due to the finish of their rods in that area. See the importance of using a stretch gauge. Luckily a 3/8" bolt in an A-Series is totally overkill as long as its tight, same bolts are used in Chevy V8 race engines with 4.000"+ bore

[Spider]

" Kit Instructions, Torque Values, Stretch Values

Lost your kit instructions? Want to check a torque or stretch value?
Enter your kit number in the field below and click “Submit.”

Important: if you have an aftermarket connecting rod with an ARP bolt, please use the chart below to contact the rod manufacturer for the stretch/torque value. The calculation of those values is solely up to the rod manufacturer. "

http://arp-bolts.com/p/instructions.php

[App K]

" Kit Instructions, Torque Values, Stretch Values

Lost your kit instructions? Want to check a torque or stretch value?
Enter your kit number in the field below and click “Submit.”

Important: if you have an aftermarket connecting rod with an ARP bolt, please use the chart below to contact the rod manufacturer for the stretch/torque value. The calculation of those values is solely up to the rod manufacturer. "

http://arp-bolts.com/p/instructions.php

Thanks, I had already checked that one out but for some reason the numbers don’t tally. I’ve arived at 32ft lb with a bit of detective work, but unless somebody thinks NO NO, then 32lb it is.
Cheers for the input.

[Spider]

but unless somebody thinks NO NO,

I'll say NO, NO.

Don't guess.

Contact SC.

[360gts]

I agree with what Mark contributed to this discussion a while back.

Mark wrote a response in an earlier thread regarding this.

Here is his quote
"Right, I have used many ARP fastners over the eyars & I have alwasy followed the instructions. I have however alwasy ignored the bit about using the "Bolt Stretch" method of determining the torque.
Having read the above I decided to see what the "Bolt Stretch" method actually entailed & having read the instructions, I seriously doubt whether anyone ARP Included have EVER used this method to tighten Mini Con Rod bolts up!"


I know many other racers who use ARP bolts (on larger engines etc.) and none of them have ever used the stretch method of tightening.
Stretch measurement may be advantageous when using larger diameter/length bolts....just my opinion.