ARP rod bolt installation SNAFU
 

I'm helping a friend install rods with new ARP rod bolts on a 3.2 crank. We got to the first one, and after stretching only .05" we could barely move the nut, and then the box end wrench started rounding out the nut. :confused: Threads and shafts were well greased with ARP assembly lube.

We used a 12mm 6 point box end wrench. The 12mm 12 point is too big, the 11mm 12 point box end fits about as well as the 12mm 6 point.

So, rather than use a 12mm as recommended, turns out an 11mm 12 point socket works, with frequent stretch measuring.

JB

Jim, that sounds like par for the course, see my prior thread on the same thing here:

http://forums.pelicanparts.com/911-engine-rebuilding-forum/379187-assembling-1966-901-05-engine-phase-i-bottom-end.html

OK, what part number for the bolts? The ARP catalog says 204-6005, which are the M9 bolts used on the 3,2. Is that what you are using? The stretch spec is 0.0120" according to their catalog. You stretched to 0.05" on the first one or about 4x the correct stretch. I would be surprised if the bolts haven't taken on a permanent elongation, check their length against the pre-stretch length, they are probably junk. What was the torque wrench reading when you did this, it should have been a clue that the stretch was too great. What stretch gage?

OOPS. I made a typo - .005 was as far as we got with the 12mm box end, using the ARP stretch gauge.

After we got the correct socket (11mm 12 point), and put it on a torque wrench, all went well. First torque to 42 pounds generally got us to .009. Final torque needed to stretch to .012 was about 55 foot pounds.

We still want to replace the nut that we damaged. The pre and post incident bolt length measurements are identical.

JB

PS: we shoulda read that other thread first! It was bang on!

This is why I tend to keep junk rods kicking around as well to help burnish the threads by stretching/torquing a few times. I've had this issue before as well and now just keep a nice "new" wrench with a welded extension handle on the open end of it for leverage. Good for rod nuts/bolts because it hasn't been worn down from years of use in other avenues :)

Sounds like you're all good to go now though :)

Almost... there was the "incident" with the rubber mallet and my little finger while separating the rod ends...

Mallet: 1
Finger: 0

I should post a picture.... :mad:

JB