magnesium crankcase reclaiming
After many years of heat up and cool down cycles these cases distort. The only way to build a 911 motor without oil leaks is to start with a crankcase which is square and true.
Our Process
Our process at Autofarm starts with cleaning of the bare crankcase with all the studs removed. All surfaces are cleaned and dressed of any damage and marks.
The crankcase is then set up on a CNC milling machine and dowel holes are drilled at the main bearing lands. This is known as Shuffle Pinning. This ensures that the main bearing housings are in line.
The next stage is to line hone the main bearing journals. With age they go oval. The layshaft journals are checked for any distortion. Next we deck the crankcase (machine the cylinder to crankcase mounting face). This is carried out on the milling machine.
We then drill, tap and fit timeserts (also known as case savers). When Porsche used aluminium cylinders with steel head studs the expansion rate of the cylinder was greater than the steel stud. The result was that extra pulling pressure was allied to the threads in the crankcase and the threads pulled. This is not always needed with engines fitted with Biral cylinders as the expansion rate was far less.
The final stage is to remove all the core plugs and clean all oil ways. We then check the operation of the oil squirters and replace them if needed. It then goes in a hot wash cleaning tank for several hours. We then machine up and fit new core plugs.
