I've been searching for ARP stretch specs for connecting rod bolts and 2-bolt main studs. I've located the connecting rod specs but haven't found anything on the main cap studs. Do any of you happen to have this spec or know where I might fi nd it?

Thank you.

How to you check stretch on main studs? Do you keep a indicator on the end while turning with a wrench?

I've used a bunch of he ARP main studs on both BB and SB Mopars, never seen mention of a stretch length for them in the instruction sheets
Finger tight installed into the blocks and the torque reading in Ft. Lbs. with their moly is all I remember reading on the instruction sheets now.
I do have several of those sheets saved out in my shop so maybe, if I can remember, I'll dig one out and copy it and attach it to this post tomorrow

Been a few too many years 4? to recall but the last set of arp rod bolts I put into oem type rods were either tq or stretch and came with an instruction sheet with specs n stretch.

If your trying to stretch your rod bolts I think you can find it in this link with your pn. I pre stretched mine twice then set the third time, not sure if it was needed but its still running.

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

I'll probably just contact ARP directly to ask them about the main studs. I checked 2 of my old ARP boxes and the instruction sheets were gone.

I’ve also never seen info on checking stretch on main studs. I’m not even sure how you would be able to measure.

For studs, the surface of the washer facing the block needs to ve scuffed with 500 grit sandpaper so it grips the cap or head surface. Just lightly scuffed so the washer can' t be turned by the nut. According to ARP 85 percent of torque goes to overcome friction, so using plenty of lube is vital in getting the right load on the studs or bolts.

Here is what I have for the ARP SB Wavelock rod bolts: TORQUE => 55 ft-lbs, STRETCH => .0070-.0075

...and here is what I have for the ARP SB Main studs: TORQUE => 110 ft-lbs, no STRETCH value provided

In comparison the Eagle H-beam rods which use the Eagle specc'ed ARP 2000 are: TORQUE => 75 ft-lbs, STRETCH => .0064-.0068

See attachments.

I hadn't seen or found main stud stretch data either but the shop I'm using indicated they use it when it's available. I can't see why you couldn't simply measure off of the end of the stud for stretch (after the thread clearance had been taken up between the block female threads and the male threads on the stud). However, ARPs reply back to me this morning indicates using the torque value is what they suggest.

Hmm, my thinking was a bit different. Given the amount of stretch you'd expect to see I think it would be hard to consistently locate the stud well enough in the block to always take up the extra "wiggle room", and therefore give you a stable baseline measuring and starting point. After all, they normally say "put the studs in finger tight", and when the total stretch may only be 0.025" (guess only, but I'm comparing to a rod bolt that's typically in the 0.006-0.007 range) there is just too much room for an error to creep in when simply installing the studs.

So instead of the above I was thinking of using the OAL of the stud as an indicator to see if the stud was over-stretched, along the lines of the rod bolt check you'd normally do. For that to work you'd need some kind of a range from ARP that says: if the bolt OAL increases beyond this point that means it's lost it's ability to retain torque.

If that info was available you'd be able to torque it down to the advertised torque (110 ft-lbs in my case), and periodically (during refresh perhaps) pull the studs to re-measure the OAL to see if they were stretched past their initial length and therefore are suspect and should be replaced.

ARP use to suggest measuring and recording the over all length on their replacement rod bolts and nuts before installing them and stretching them, I've seen the same thing on some Manley rods also, I think
I have seen some differences in the new lengths on the bolts in a set, maybe from .0010 to .0028 I use a stretch gauge on the bolts in the rods in a rod vice before and after tightening and sneak up on the torque 5 lbs. at a time to get the torque needed to be in the middle of the stretch specs
I've over stretch some of Molnar rod bolts by starting off at 55 Ft. Lbs. on their 7/16 ARP 2000 rod bolts
ARP wouldn't do anything about that set or those two bolts