ARP Con Rod Bolt Query

[AlfaLofa]

I have recently had my con rods and pistons balanced.

When I sent them off I used a set of new ARP bolts (only finger tight) to attach the caps to the rods.

When I got the rods back, the bolts had been tightened such that 40 ft/lb torque was required to loosen the bolts.

The ARP data sheet states that the bolts should be torqued to 55 ft/lb using assembly lubricant.

Can I still consider my bolts to be unused (and unstretched - whatever that is)?

P.S.
What does "the con rods should always be re-sized after new rod bolts are fitted" ????

P.P.S.
I've just found this article:
http://www.carcraft.com/techarticles/11 ... ewall.html
which contains this piece of frightening information (so my bolts might be b******d):

[rgh0]

The bolts should not have been over stretched by tightening to only 40 ft-lbs. Typically you would need to go to twice that value to be at risk of yielding and stretching the bolt.

When installing the bolts use a stretch gauge if you can rather than torque and stretch to the ARP specified amount. Measure the bolt length before its installed and note it down and replace bolts if the length changes when you strip the engine next time. In a road engine ARP bolts should be good for ever and multi0ple rebuilds if not abused when installing.

The comments on resizing the rods when installing new bolts applies to the US engines that typically use a pressed in rod bolt and nut as shown in the pictures rather than the Lotus / UK Ford arrangement of a bolt that screws into the rod. The act of pressing in new rod bolts can distort the big end which is why it needs to be checked and resized if needed. This is not an issue with twin-cam rods

cheers
Rohan.

[AlfaLofa]

Thanks Rohan!

I'll get hold of stretch gauge.

[sutol64]

what is the arp bolt part # ? i need to get some ! TIA

[AHM]

You measure the stretch because the Young's modulus of a material gives a more accurate measure of clamping force than applied torque.

Re-sizing is where you machine the mating faces a few thou so that the rod is now too small - Then machine to the correct size. This ensures that it is the correct shape and size.

[CBUEB1771]

what is the arp bolt part # ? i need to get some ! TIA

Unfortunately ARP does not list big end bolts for the 125E connecting rods in their catalogue, so I can't provide a part number. However they are available from many of the usual sources such a QED, Kelvedon and Burton, assuming that you are in the UK. There are two versions available, one for standard connecting rods and one for steel rods. I am not really certain of the differences. Images on QED's web site show differences in details of the under-head section and unthreaded shank.