Excessive Shaft End Play

[Murray Parr]

The shim closest to the flywheel looks like it was installed not on center. It has been a few years since I built one of these, so I don't recall if that is possible or not.
Maybe it sheared part of the shim off when forced onto the wrong position. This doesn't however explain how the shim closest to the case got deformed without effecting the 2 in between but maybe it took the builder a couple of tries and deformed the other before putting it on.

Just a thought...

[Bryan Cotton]

Rodger posted this video:

[Raluttio]

I have become quite frustrated with my engine. I decided to crack open the case on Nathan at Sonex's advice to look around. I still have not discovered the cause of the mangles shims but the consequences are quite apparent. Every single bearing face is beaten up from all the metal shavings that were created.

I have put photos and videos of the internals in this Google Drive folder including the video that Bryan linked: https://drive.google.com/drive/folders/ ... drive_link

I consulted with the metals and automotive teachers that I work with. I made some v blocks and checked the flywheel and crank with calipers and a dial indicator that is accurate to .00005" and have not found anything that is out of spec. Just a few of the measurements I've done that I can remember off the top of my head: Measuring from front bearing to the thrust bearing longitudinally there is less than .001" of play. The main journal and front journal both measure an amazing .00000" - essentially both are perfectly round. All of the connecting rods are .018" or less in side to side clearance with no detectable up and down movement. The thrust bearing itself measures less than .0007" in runout on the internal diameter and less than .001" variance from the lip that the shims run on and the lip inside the case. I measured this thing in every way possible - very methodically multiple times on 3 different days. I repeated all measurements multiple times to ensure reproducibility so I am confident in my measurements.

I might still take it to a machine shop and have them check but I can not find anything wrong with the internals.

New question and new problem now that I know about the damage caused by the shredded shims - is the crank salvageable given the scoring that has been caused by the metal shavings? When I run my finger nail over the journals I can just ever so slightly feel the ridges. My finger nail doesn't catch - I can just barely feel the roughness. If I polish up all of the journals and replace all of the bearings will everything be ok or does polishing take off enough material that I would need undersized bearings? How would I deal with the two single piece bearings on either side of the timing gear - I'm not sure the prop hub and timing gear will come off given they are interference fit.

I have looked all around on forums - including The Samba - and I can't find a single case of someone having their shims shredded. This is particularly frustrating given this engine has less than 50 hours on it. Engine logs do show all oil changes during break-in were performed at the proper times.

[Area 51%]

If the oil pressure was adequate before teardown, I suspect a "dry" first start to be the culprit.

Common wisdom would have you remove the spark plugs and crank the motor till the oil pressure comes up to fill the galleys and provide enough lubrication for the first start.
Better than nothing, but an outside pressure source, and slowly rotating the engine till oil emerges from the rocker arms is a safer bet.

Remove the hub and replace the one piece bearings if you're comfortable with the condition of the crank. Probably cheaper to replace the crankshaft than have a shop rework it though.

[Bryan Cotton]

If the oil pressure was adequate before teardown, I suspect a "dry" first start to be the culprit.

That seems plausible!

[Raluttio]

For those who may come across this in the future I have a wrap up.

I conducted a major overhaul which included a new crank, all new bearings, new cylinders, new pistons, new gaskets. All of this was necessary due to the metal shavings that were created by the end play shims being ground up and sent through the engine in the oil. I still do not have a confirmed cause of the shims being ripped apart other than what I previously speculated.

One more piece to the puzzle came into play - and may be what caused all of this - after reassembling the case and calibrating the oil level. The full mark that the previous owner had set on the dipstick was just above the 2 quart mark - maybe 2.2 quarts. I am confident now that this engine had been run with too little oil.

I had first run of the rebuilt engine two days ago and first flight was yesterday. The engine runs much smoother, is able to idle lower, and I am able to run lean of peak - something I could not do before.

I still need to:
-Adjust the timing of the secondary ignition.
-Cover up my oil cooler more - oil temperature is still only getting to 140 even on a 90 degree day during first flight!
-Investigate further my #1 EGT running 150+ degrees hotter than the other 3 - had to manage the mixture to keep it below 1400 while the others were 1300 or below. This is something that was occurring before the rebuild. It is a new probe at rebuild and I can see discoloration of the metal at the 1hour oil change so I am confident that it is not an instrumentation problem. I cleaned up all of the mating surfaces between the head and the exhaust. I lapped every single valve while the heads were off so I can’t imagine it’s a leaky valve.
-investigate a faint oil smell in the cabin. I only saw slight weeping from the oil cover after an hour (didn’t tighten the nuts enough) so I’m not sure of this source.

I feel as though I will continually be tinkering. HOWEVER - I am ecstatic to be flying again!

[Bryan Cotton]

Great news Rodger! Our #1 EGT is always a lot hotter than the other 3. Nature of the beast. Hard to get a good balance. And yeah we always smell oil inside. Actually anywhere within 30 feet of the airplane, especially when hot.

[Raluttio]

Thanks for the insight Bryan. I flew again today and for a while #1 egt was 300 degrees hotter than 4 which was the coolest. The #1 Egt is always the coolest so I assume it’s running rich. I’ve seen a bit of the discussions around trying to balance out temps. Sounds like making it a turbo is the only real fix!

I’m still leaking oil from the sump cover and I noticed a small drop on the bottom of the pump cover. Hopefully it’s from the cover and not the pump to case interface. I didn’t use the gasket between the pump and cover plate like the manual shows but maybe that’s a mistake.

I also adjusted my secondary the wrong way - had a noticeable decrease in performance today.


I’m just happy to be flying though.