I had the connecting rods refurbished by Tom Cutter at Rubber Chicken Racing Garage. The rods can stretch with high miles so the distance between the center of the big end and little end is not correct. It’s possible for the rods to twist so the wrist pin is not in the same plane as the crankshaft journal. Tom inspects them and has any machining done to correct these problems with the rods. Since I’m installing new pistons with new wrist pins, I had Tom replace the connecting rod small end bushings and ream them out to the correct clearance for the wrist pins.
The rod bolts are “use once” as they are designed to stretch when installed, and I am replacing the rod crankshaft bearings.
|11 24 1 258 460||BEARING SHELL, Standard Size||2|
|11 24 1 337 553||CONNECTING ROD BOLT||4|
The rod bolts have a special 12 point serrated face. They require a special bit that fits. I got this one at my local NAPA store.
Here is a short video summarizing the installation procedure.
VIDEO: 1983 R100RS Install Connecting Rods & Cam Followers
Preparing The Connecting Rods
Here are the connecting rod parts. The wrist pin fits into the small end of the rod to attach the piston. I won’t need it to install the connecting rods.
I marked each rod to indicate the side it came from. Tom marked them again when he returned them.
The rod big ends that fit on the crankshaft journal have bearing shells, one for each half (only two are shown as two are already installed in the upper rod). There are four special rod bolts.
The connecting rods have locating pins that hold align the two halves. There are corresponding holes on the rod end caps.
The rods go on the crankshaft so the face of the rod with the pins faces to the front of the engine. I mark the small end of the rod with an arrow so I won’t install it backwards.
Install Bearing Shells
The connecting rod and the rod end cap have a slot machined into them. This mates with the ridge of each bearing shell.
The bearing shells are a press fit into the 1/2 circle of the connecting rod and rod end cap.
I keep my fingers off the bearing surface as oils in finger prints can corrode the bearing material.
Lubricate Bearing Shells and Rod Bolts
The bearing shells need to be lubricated to protect them on the first engine start. I use engine assembly lube with Moly-graphite, which works well in this application. The rod bolts and the threaded holes in the rod cap are oiled with a light oil. I use 3-in-One oil.
I put a generous amount of engine assembly lube on the bearing shells.
After I lubricate the bearing shells and the rod bolts, I put engine oil liberally on the crankshaft journals.
Install Connecting Rods
I use a 13 mm long socket to hold the serrated rod bolt bit. Since the cylinder studs stick out quite a ways, I use two long socket wrench extensions so the torque wrench will clear the cylinder studs.
I make sure I have the correct connecting rod for the side of the engine I am working on. And I orient the rod end cap so the side of the cap with holes is facing the front of the engine.
To protect the engine case from getting nicked by the rod should I drop it on the case, I put a shop towel on the bottom of the cylinder hole to protect it.
I insert the rod end cap into the cylinder hole and rotate it around the crankshaft journal so the bottom bolt hole is facing me and hold it in place with one finger. The engine assembly lube tends to stick the bearing shell to the crankshaft journal so it’s not as tricky as it looks to keep the rod end cap on the crankshaft journal.
I insert the connecting rod and align the pins in the rod with the holes in the rod end cap and wiggle the connecting rod into the holes in the end cap. I verify the arrow on the small end of the rod is pointing toward the front of the engine.
I insert the bottom rod bolt and get it to catch in the threads a couple turns. Then I let the rod down so I can see the top rod bolt hole and install a rod bolt.
Then I insert a piece of garden wire through the small end of the rod and around the cylinder studs to prevent the rod from falling and nicking the engine case.
I tighten both rod bolts until they are snug. Then I get the serrated bit with the socket extensions. After I put the serrated bit into the head of the bottom rod bolt, I loosen the bolt 1/4 turn and then I torque it to 36 FT-Lbs in one smooth motion.
I repeat the procedure with the top rod bolt. Then I do the same thing on the other side connecting rod.
Install Cam Followers
I put the cam followers in bags marked with the side and exhaust and inlet so I would be sure install them where they came from. I put engine lube with moly-graphite on them and install them in the correct push hole in the engine block.
HI,following your posts and videos,even with no projects in the works,still cold in NH and no workspace.I enjoy your attention to detail and camera work.I have a quick question,if I may.What do you recommend for cleaning oxidation from engine cases,or do your projects just involve bead blasting?Thank-you in advance.Don C
I’m pleased I’ve been able to provide some winter entertainment. 🙂
I would NEVER bead blast the engine cases, transmission or rear drive-full stop. Glass shards will go everywhere including stay embedded in the aluminum. Vapor honing/blasting is an alternative, but you will have to completely strip the engine including all the oil passage and freeze plugs so you can clean all oil passages and every nook and cranny. You would also have to completely strip a transmission and a rear drive for the same reason. If you don’t absolutely get all glass out of everyplace, expect to replace every bearing, a crankshaft, connecting rods, etc. in time.
Here is a document that covers methods I use to refinish.
–> 51 BMW 1973 R75/5 Refinishing Techniques
I hope this helps.
Thanks for the quick reply and the links.Don C