Sunday, October 8, 2017

Cam Installation Attempted

Today I planned to transfer the helical shaft from the old intake cam to the new part and then install both cams. Unfortunately, I ran into two issues and achieved neither goal.

Yesterday I found the torque spec for the helical shaft in the TIS (40 Nm plus 60 degrees). I could not find any indication that the shaft is torqued to yield and must be replaced if removed, but the cam installation document does indicate that the shaft can and should be removed if "applicable", which I take to mean, "if necessary". Because 40Nm plus 60 degrees is likely no more than 60-70 ft*lbs, I assumed it would be relatively easy to remove the shaft. I was wrong.

The new cam carrier out of the box shows absolutely perfectly machined lifter bores with a chamfer on the bottom edge. The ty-wraps are keeping the caps in place. In the background is one of my new cams.

I had previously used a piece of copper wire to keep tension on the primary timing chain so it wouldn't fall off the crank sprocket, but that proved less than ideal. I replaced it with a bungee cord today.

The TIS cam installation literature points to a torque document that lists four different cam stud sizes and the appropriate torque spec for each. I measured the studs to find mine were M7, which calls for 14 Nm (10 ft*lbs).

The cam carriers were labeled with manufacturing data, including the manufacturing date. It appears BMW is working off of 10+ year old inventory which likely means these are not a big seller.

One of the messier jobs is pulling the lifters out of their engine oil bath and placing them in the cam trays. The magnets are covered in blue tape to protect the mating surfaces.

If you look closely you can see how far away the bearing caps are displaced from the carrier by the cam. Although this appears to show several threads exposed, this is due to the caps not being level.

I fastened the cam vertically in my vise and attempted to use my largest breaker bar and 10mm allen socket to break the shaft free of the cam but the shaft refused to budge. After a few more failed attempts, all the while watching the breaker bar bend and my rather heavy table move in response to my inputs I decided to try something a bit more persuasive -- my IR impact wrench. I sat on that for several 10 second periods, fearful each time that the attempt would culminate in the destruction of my allen socket (which is not impact rated) but nothing happened. And I mean nothing. I watched the shaft like a hawk and it remained locked to the cam. I assumed at this point that the shaft had been "work tightened" far beyond the original specification or high strength thread locker (i.e. red Loctite) was used when it was installed at the factory. The TIS does not mention using thread locker on the shaft, by the way.

In an attempt to salvage the day and secure the primary timing chain I decided to install the exhaust cam. Before I could do that I needed to clean both cam carriers and cams themselves, as well as install the lifters in the exhaust carrier. Using the magnets once again to retain the lifters in the carrier I was able to pick up the assembly from the bench and slide it down the studs in the head easily enough. I then installed the cam with the 3rd and 5th lobes barely pressing on the appropriate lifters and installed the corresponding bearing caps on the studs

After repeated attempts to secure the nuts, however, I realized that an insufficient number of threads were exposed on the studs. I was able to catch one of the nuts with perhaps a single thread only to see the cap rotate on the cam just enough to cause the other stud to fall below the top face of the cap, making it impossible to install the other nut. Although its clear the fully expanded lifters are in part to blame for this, as evidenced by the fact that the entire carrier rocks back and forth a bit as the lifters pivot on the top of the valves, I'm not sure why others have been able to use the alternative methods to install the cams and my attempts failed. At the start of this project my technician graciously offered access to any and all BMW special tools I'd need to complete the project so I am now planning to borrow the cam installation tool to complete this task.

Of course, before I can borrow the special tool to install the cams I'll need to address how to remove the helical shaft from my intake cam, assuming I still want to do that. I am planning to sell my old cams and after this experience I can't imagine anyone wanting to deal with the same hassle, so I am now considering the purchase of a new helical shaft and selling the old cam with the existing shaft. I already checked the price of a new shaft and it's a pittance with my discount but the real issue is whether it's available in the US. If it has to ship from Germany then I'll be more likely to ask my tech to remove the shaft because otherwise I'll be looking at another 7-10 day delay before I can resume the assembly process. Until I resolve these issues we'll be holding at ProCon (Project Condition) Yellow. :)

Next Up

Tomorrow I'll check the availability of the helical shaft with my parts rep. If it's available in the US I'll order the part and arrange with my technician to borrow the special cam installation tool. Once the cams are installed I'll be able to time the engine, install the vanos, and wrap up the build.