Case savers too tall

[lutorm]

I just realized that the "case savers", the threaded inserts for the head studs, are protruding above the cylinder flange in the case, so the shims had actually been resting on the inserts rather than on the flange, and the cylinders could rock back and forth. I very carefully had to grind them down so they don't protrude above the flange plane.



Has anyone else noticed this? This seems like a recipe for a leak, not to mention having the deck height change with time as the shims get squished into the inserts (the old shims have clear indentations where they had been resting on the inserts).

[SNX1508]

Yes, I had the same problem with AeroVee #0736, 6 of the 8 inserts for the right side cylinders were too high. I choose to trim the shims, as I did not want to grind on the inserts for fear of having to separate the case again to clean up the resulting mess.

Terry L. Cooper
SNX #1508
Tail Wheel
AeroVee #0736
N296SX
2005 construction hours, and was completed in October 2016
http://www.mykitlog.com/SNX1508
First engine run: https://www.youtube.com/watch?v=K9wP77I ... e=youtu.be
FAA Inspected & Airworthiness Certificate issued 11/4/2016
Sport ASEL endorsement on 8/9/2017
Tailwheel endorsement on 9/7/2017
Sonex #1508 N296SX first flight on 11/29/2017

[Area 51%]

The factory took the liberty of turning some of the case savers in an extra 1/4 turn just for that reason on our block.

The problem with that approach is; the case savers had been machined to clear the connecting rods inside the block. With that 1/4 turn, the edge of the saver is now in a position to require additional material removal. Further......there is less thread engagement between the saver and case in those locations.

I like your approach better. Any reason you didn't just clearance the shims instead?

[lutorm]

Yeah, my initial idea was to clearance the shims, too. However, they are a loose fit on the cylinders and can move around quite a bit. To make absolutely sure they'd clear the inserts, I'd have to almost cut them off. I also didn't want to have someone remove the cylinders in the future and not know to make sure the shims went back correctly (or change shims and not clearance them). It was actually pretty easy to take off the material with a small sanding wheel on the Dremel, took maybe 30s per insert, although you need steady hands... (And my case is already apart so I don't have to worry about getting the swarf out.)