[Grady Clay]

David,

Installing the rings will help square-up the piston in the cylinder. Daubs of putty between the solder will help also. If you use your new rings, be sure to grease everything for testing.

I will speculate you will get dramatically different clearance numbers with the rings installed and eight measuring pieces.

In your first image, is that tool chatter on the angle cut? If so, I recommend getting it smooth and slightly radius the corners. How well does the head transition from flat to angle and fit the piston? Exactly where is the closest clearance? This is a critical issue.
While you can run the flats of the piston and head somewhat close, it is the clearance at the angle cut on the head that needs particular attention. The clearance measurement at the angle is perpendicular to the surfaces, not the axis of the cylinder. That clearance should be slightly more than the flat “deck” clearance around the perimeter of the piston.

You can see how robust the piston is above the top compression ring. This is an indication of how concerned the engineers are about collapsing the piston and grabbing the ring.

I don’t have a problem with multiple copper cylinder base gaskets. I’ll try and find the custom gasket supplier.

When you think everything is done, I would cc the combustion chambers to verify all are equal and as expected. The twin plugs will help a lot with many combustion issues. I assume you know you don’t need to have as much spark advance as with single plugs. Make sure the sparkplug pockets are not-too-smooth transition and all are equal. Indexing the sparkplugs may help depending on type.

I would recommend some data acquisition; particularly boost, head temperature, and knock sensing. This will let you get the most from your 930 without damage. If you track your car in hot weather, I recommend the “Rubbermaid Solution” times two.


Best,
Grady