The top item on my To Do List for the winter break from track events was to replace the rod bearings. I (and many others) have discussed how the #2 rod bearing on the 944 engine seems to be particularly prone to failure. (See 944 Oiling System Explained). These particular bearings have been in the engine for 2 track seasons so I felt, based on nothing more than caution, that it was time to replace them.
I have done the job in the car once before and knew that it was a little awkward to work from underneath the car but not too daunting. I use a very crude rig to support the weight of the engine, basically a 2×6 board spanning across the shock towers and a rigging sling wrapped around the board and around the inlet manifold. I didn’t take any pictures but here is a rough list of steps to perform this job.
- Disconnect the battery
- Disconnect the oil filler tube from its clamp on the inlet manifold
- Remove the spark plugs
- Put the car up on a lift or jack stands
- Remove the front wheels
- Drain the oil
- Remove the sway bar
- Disconnect the steering rods from the wheel hub
- Disconnect the A-arm from the engine support cross member (long bolt at the front, 2 short bolts at the rear of the arm)
- Tie the wheel, A-arm, and strut tower assembly back out of the way
- At this point, you must support the weight of the engine. The way I did it with a 2×6 is discussed above and this works well for me.
- Remove the connection of the steering shaft to the steering rack
- You can now remove the 4 bolts holding the engine support cradle and drop the cradle, with the steering rack attached
- I have a low mount alternator (A/C delete) and found I had to remove the alternator belt and use the tensioning rod to push it back to access one of the oil pan bolts.
- Remove the oil pan attach bolts. Don’t forget the 4 longer ones at each outside corner
- At this p0int, the pan should drop. You will have to wiggle it from side to side to get the oil pickup ring to clear the opening in the pan baffle
- Rotate the crank so that 2 rods are at their lowest point. Un-torque and remove the rod nuts.
- I find it easiest to insert a long rod into the bottom of the piston and tap it with a hammer to force the piston up and release the rod bearing cap. Note the orientation of the cap.
- NOTE: On my car, the “tang” on both rod bearings went on the passenger side of the engine. At one point I got a cap on the other way. It would go on but the crank wouldn’t rotate when the cap was tightened. I assume this a standard orientation (tangs on the passenger side) but it is best to note carefully on your car the position of the tangs on the bearings as you remove them.
- I unpacked my new bearings and washed them carefully with brake cleaner. I used a micrometer to check the thickness of the old and new bearings, just looking for gross differences, of which I found none. The measurement is a little tricky because you are on a curved surface. Measure from a consistent location and just look for big (>0.0o5″) differences.
- You are ready to put the new bearings back in. I coat each bearing shell with assembly lube. I leave a small space between the rod and the crank, put the bearing on the bottom of the crank surface, and rotate it 180 degrees into position opposite the rod. I pull the rod down over the bearing. I use a small screwdriver to push the bearing shell flush with the rod parting surfaces.
- Then I mount the rod cap and pull it up into position. The parting surfaces of the rod and the cap should come together without any undue force.
- Re-install the nuts for the rod studs. I like to use new nuts every time and I use the new style “Versarub” type.
- Torque them to the spec in the workshop manual.
- Check to ensure that the crank rotates easily. If the spark plugs are pulled, there should be minimal resistance.
- Repeat for the other rod. Then rotate the crank 180 degrees and repeat for the other 2 rods.
- While I was in there: I inspected the oil pickup tube for cracking. I also verified the torque on all the remaining fasteners for the crankshaft girdle.
- Clean out the inside of the oil pan and clean the gasket surface.
- Putting the oil pan back on is a pain the in the ass and methods to make it go smoother have been discussed by various folks. My only trick is to get it started with 1 bolt on each side near the midpoint of the pan, using the long bolts that will ultimately go at the corners. Then carefully check the position of the gasket. Then work to insert the shorter bolts from the center outward.
- Torque the bolts per the workshop manual. They say 2 passes. Hah! It’s like whack-a-mole. Trust me, you’ll have to make multiple passes before all the bolts are torqued about the same. And Porsche, what’s up with the 2 bolts that can only be accessed by a wrench. How are you supposed to torque those?
- Once you’ve got the oil pan in, then as they say assembly is the reverse of dis-assembly.
- You take a lot of things apart doing it this way. The good news is that it is a perfect time to check and re-torque all of your suspension fasteners. For instance, I found a couple on the sway bar that were working themselves loose. I mark all my bolt heads with a white paint stick, both as a reminder and as an easy inspection point at the track. There are 3 piece engine support members sold on the aftermarket but no more than I am doing major jobs like this I don’t really see the value.
So now for the unexpected. When I went to clean my oil pan, I found that the welds of the aftermarket installed oil return “trap door” had failed and the piece was laying in the bottom of the pan. Also, the OEM plastic baffle was broken. I had purchased this Series 2 oil pan off Ebay and did not install the trapdoor myself. (The piece I’m talking about is as is sold by Lindsey Racing and others. It has a little one way trap door that attempts to keep more oil around the pickup during hard cornering. It has to be welded to the pan. All I can say is that this weld is trickier than it looks!) Purely subjective take-away is that this trap door must not have been mission critical to the life of my engine. I left it out this time but did replace the OEM baffle with a replacement that I had in another oil pan in my stock of parts.
And as to those bearings. Here is a picture of them. They don’t look bad to my eyes. And the #2 bearing looks the same as the others. But piece of mind is important and I”m glad I did this job. Note: I use Valvoline 20-50 full synthetic racing oil and change it after every other track event. There was a little sludge in the pan but otherwise the bottom end looked very clean.