The purpose of having an arc billet rod in your predator 212cc or other small engine is to prevent the connecting rod from failing when the governor is removed. This installation guide will show the torque specs for the billet rod, and how to measure the oil clearance so you can safely rev to high RPM’s without throwing your rod. Affiliate links to the tools and arc rod are in the article and help keep this site running.
Choose the Right Aluminum Billet Connecting Rod
For most applications (unless you are building a stroker, or are an advanced builder) in order to get the ideal performance, you will want to choose a stock (original size) length connecting rod. You can click predator 212cc billet connecting rod to find the exact one on ebay for both hemi and non-hemi versions of the predator 212cc engine.
Seat the Bearings with the Proper Torque Specs (170 inch/lbs oiled)
The connecting rod will come with installation instructions. You can’t just put the rod in the engine, and wrench it down. You need to use an inch pound torque wrench with a 1/4″ 12 point socket so you can torque the connecting rod bolts down to spec.
- Disassemble the connecting rod, and insert the bearings in the grooves with your fingers, (they press fit in later).
- Wrap a sock or cotton rag around the small end of the connecting rod, and place it in a vise so it can hold the crank while you are torquing the bolts.
- Put the crank journal on the long half of the connecting rod, place the other half of the arc connecting rod over the top of the crank journal.
- Oil the connecting rod bolts.
- Torque specs indicate 170 inch pounds. Start by hand tightening the bolts, then switch between bolts every 20 inch pounds until they stretch and top out at 170 inch pounds.
- You have officially seated the bearings in the rod. Disassemble the rod from the crank, and clean off the oil from the journal and bearing faces.
Measure Oil Clearance
Measuring the oil clearance between the crank journal and connecting rod is critical. Luckily all you need is some plastigage. Plastigage is basically a thin piece of plastic that will compress to a certain width depending on how much it is compressed. The package itself shows you what the clearance is. For my particular build, the red plastigage was all I needed.
- With the rod half and crank still in the vise, cut a small piece of plastigage, and put it on the crank journal.
- Install the other half of the connecting rod, and torque to 170 inch pounds (make sure the bolt is oiled).
- Disassemble the rod from the crank and hold the supplied plastigage packaging to the smashed plastigage, and you have your oil clearance number. If the number is within spec on the instructions, you can reassemble the crank and rod inside the engine.
Attach Rod to Piston and Assemble In Engine
Install the wrist pin and piston to the connecting rod (making sure you orient the rod so that the dipper scoops oil as it rotates), then insert the crank into the engine case. Using a piston ring compressor, install the piston rings 120 degrees to eachother, and the rod to the crank journal. This will be the third and final time you will tighten the connecting rod bolts (oiled) to 170 inch pounds.
Thanks for reading this article about installing an arc billet connecting rod. If you found it beneficial, please feel free to link to and share it. I will be posting more performance part installation articles in the near future, so be sure to check back on my main predator 212cc performance mods page for updates.