I am in the process of rebuidling a 1983 911 SC to address broken head studs. While I was there, I had the heads reconditioned, which included a fly cutting (0.25 mm of material removed from heads) to clean up the mating surface between the cylinder and head. I am now in the process of installing the pistons and cylinders. Initial base gaskets were 0.25 mm, so I installed 0.50mm base gasket to make up the difference. I would expect that this would take me back to the clearance that existed before the teardown. I have installed P&C #1 and 4 and have begun the deck height check. I started with the acid core solder (2 mm in diameter) at the 3 and 9 o'clock positions on the piston. Installed and torqued the heads and rotated the crank. The result is that the solder did not compress at all, indicating a clearance greater the 2 mm. I tried the same thing with teflon putty and this indicated a clearance at 20-2.25 mm. I then took a vernier caliper and measured from the top of the cylinder to 3 flat spots on the piston head for each of the cylinders and came up with a reading of 0.045 to 0.05 in (approx 1.25 mm).
What gives? Which number is correct? Does this type of piston not lend itself to the solder measurement
Any help is greatly appreciated.
Rick
