Some valuable information concering quality and possibly safety of j-nuts! GM part # 3892755, found in 68 AIM page 66 (UPC 4 B1), attaches the front leaf spring bracket to the underneath unitized body. The j-nuts that have both quality and supply peace of mind concerning safety are the ones imprinted with a "CIP" and can be purchased through AMK. There are other similar generics that look similar but upon closer inspection they have issues and when you go to torque to the required 20 to 30 ft. lbs. you have risk of the thread pulling. Non CIP clips I looked at did not have full thread, and had less threads by up to 50%. This is not meant to communicate anything other than a CIP clip is junk, only that inspection and thought to where you purchase might be the prudent thing to do. In fact, not "might be" but "will be" the prudent thing to do. Let me tell ya what happened and then read an older post I found but found after the fact.
Remember recently I took the dummy rear out of the car and installed the original re-built 12 back in. After paint to install the dummy rear some new generic j-nuts were installed and used. When I took the dummy rear out I noticed the new j-nuts in location as the originals I had taken out when the original rear was removed. When I installed the orig. rear back in all six of the screws started nicely (3 for each bracket) and I hand snugged/tightened with a normal length 1/2" rachet and socket. Everything was fine or so I thought. After the rear was installed I later got under the car to torque those rascals to the required 20 to 30 ft. lbs. Set the torque wrench to 20 ft. lbs. and started to tighten but the bolt turned and turned. Realized quickly something was wrong. Went to another j-nut/screw and tried that one with same results but I gave it one or so more and I heard a pop sound. The thread had wiped off. Luckily the screw backed out like nothing happened and dropping the front leaf spring perch is pretty easy but the j-nut was junk. Ended up changing all three on the left side with 'CIP' j-nuts and guess what, they torqued with no issue. Went to the right side and tried to torque one with same negative result. Just decided to drop that front leaf spring eye and change those 3 j-nuts immediately. After changing the right side, all three torqued with no issues. Here are some pics showing differences and another write up found after the fact. Lesson learned by me that could save some of you some time and again possibly safety!. Still available through GM but the part # changed to 378276. AMK uses that 378276 part # in their catalog as well. http://www.gmpartsdirect.com/results.cfm http://www.camaros.net/forums/showpost.php?p=1288560&postcount=94
Old used CIP to poor quality copy-Notice the nose dimension difference.
Notice the thread form and amount of threads!
New CIP nut to left vs. some generic problem nut.