Connecting Rod FAQ

We have compiled many common questions or misconceptions about connecting rods into this page. Hopefully it will answer your question right away and get the information you need in your hands.

Bolt Torque:

There are two common ways to torque connecting rod bolts. You can either use a GOOD torque wrench, or you can use a stretch gauge. Either way is effective and simple. Using the torque wrench, simply grease your bolt up with ARP Moly assembly lube, and thread it all the way down in the hole. Torque the bolt to the recommended value. Then, loosen the bolt. Torque to the recommended value once again. Break the bolt loose one last time, and finally torque it to the recommended value and leave it alone. This process wears down any small burrs on the threads and seating surface of the bolt and rod, ensuring the most consistant final torque. If you are going to use a stretch gauge, lube the bolt up with ARP Moly assembly lube and thread it into the rod.Make sure your crankshaft is in a position where you can phsyically put the gauge on the bolt. The bolt has a dimple in each end that allows the gauge to stay centered and in place. Put a long wrench on the bolt, and put the gauge in place, zeroing the dial. Begin to tighten the bolt until it has reached its recommended stretch.

3/8" ARP 2000 Bolt
5/16" ARP 2000 Bolt
50 ft-lb Torque
26 ft-lb Torque
.0055" Stretch
.0055" Stretch

If you are unsure which bolts your connecting rods came with, and you lost the paper which comes with them, please email

Wrist Pin Fit:

This is a mystery for many novice engine builders and we do get questions about it fairly often. Our connecting rods are ground with a tolerance of .0003" on the wrist pin bore. However, they are sized intentionally on the small side. This is done because a loose fitting wrist pin is totally unacceptable. The consequences of this are that if you pair a rod on the small side of the .0003" tolerance with a wrist pin which is on the big side of THEIR tolerance, they may not neccessarily fit. DO NOT FORCE THEM, the pin is designed to float and turn inside the rod. There are two courses of action here, first, especially on the rods with tapered small ends, it is very easy for them to get burrs on the edges of the bushing. Check for and remove any burrs there, and see if it will assemble. If not, see if there is a different combination of wrist pins to rods out of your set that will assemble all of them. You may be able to pair a small pin with a small rod so to speak right out of the box. Lastly, bring your rods into a machine shop and have them honed to fit the wrist pins. This is very cheap, and very very very little material needs to come off. This whole process is a neccessary evil in order to avoid potentially loose fitting wrist pins.

Big End Fit:

The biggest cause of failure in connecting rods is from engines that are assembled with incorrect clearance between the bearing and the crank. This can be avoided quite easily by proper assembly techniques. The easiest and quickest method to check clearance is to use a product called "Plastigauge". It is available at the parts counter at virtually any auto parts store. To use plastigauge, snip off a piece approximately the width of your rod (or main) journal. With the journal dry, carefully lay the piece sideways across the journal. Put the rod cap back on, complete with bearing, and torque it to specification. DO NOT move the crankshaft in this process. Break the bolts loose, remove the cap, and there will be a smear of plastigauge on the journal. This is why it is important not to move the crankshaft- moving it will widen the smear. Using the scale on the package of plastigauge it is possible to measure the actual clearance. The other method for measuring the clearance is to use a dial bore gauge and measure the rods bore, with it assembled. Then, using a micrometer, measure the OD of the crankshaft journal. Then tape a ball bearing onto the anvil of the micrometer, measure the ball bearing. Open it up and measure the bearing shell thickness (you will need to subtract off the diameter of the ball bearing to get that number). Take the bore of the rod, subtract the bearing shell thickness (times 2), and the OD of the crank journal, and you have your clearance. Check this versus the specifications for your particular engine in the Bently repair manual. For a high performance engine it would be generally be best to be on the large end of the specification given.

Pulling the cap off:

Laugh all you want, as this seems like it should be a no brainer, but the connecting rods use dowel pins to align the cap to the rest of the connecting rod. These are a slight press fit so that the cap cannot walk around on the rod in operation, so you usually cannot just give it a superman tug and rip it off by hand. There is however a quick and easy trick to pop these off in a few seconds and look like a pro. Thread a couple of rod bolts into the rod until they are about 1/4" from bottomed out. Put a couple of fingers through the big end of the rod bore, letting the rod hang down from your hand- make sure you aren't going to drop it. Using a non marring hammer of some sort, GENTLY tap back and forth on each rod bolt. This will quickly walk the rod right off the cap, and when it comes loose it will hang from the two bolts, not fall on your foot.

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