[jashropshire]

I’m in the process of putting my ’68 912 engine back together after new big bore pistons, cylinders, and rings (and various minor repair/clean-up jobs that needed doing)

I have a deck height of 1.65mm on the left side, and 1.52mm on the right. After several attempts and various combinations of shims, that’s as close as I can get it without more drastic measures.

The left side head measures approximately 61cc’s in both chambers. The right measures 58cc’s in both chambers. Hopefully that difference is minimized now with the cylinder shims.

When removing the heads for the first time, 3 shims came off when I unbolted the rocker arm stands. (I only noticed 1 shim on the right side at the #3 exhaust valve. I found the other two when I was cleaning up the head bolts from both sides) These go on top of the head bolts. After reinstalling the right rocker stand with rockers, and adjusting the valves (without replacing the shims), I didn’t like the appearance of the #3 exhaust rocker in the way it was hitting the valve stem. It was way off (hitting at an angle on the extreme edge of the valve)

This evening I removed the rockers and rocker stand, and installed the 3 original shims all on the right side. #3 Exhaust now looks much better. I was able to easily adjust the intake and exhaust valve on #3.

The problem now is #4 rocker arms are too tight; both intake and exhaust with the piston at TDC. I can’t turn the screw out any further. I am also not certain these shims came off that side anyway. The shims, if I recall correctly, measure about .70mm.

My question is, must I have all 3 shims installed on one side? Would leaving one or two out so that I can get proper adjustment cause stress on the rocker stand when I tighten it down? Or, do I have another problem?

I am hoping to stuff this engine back in this weekend. Your usual good advice is much appreciated.

Thanks

Jeff