My Wooden Airplane
Skip Navigation Links.

7/20/2013 - 7/28/2013

Powder Coat Pushrod Tubes, Reassemble Engine

I brought the crankshaft to breakfast this Saturday, and the suggestion was made that I polish it. Now, when I bought the crank from Nitron, the instructions were specifically NOT to polish it. However, I suspect that there might have been some contamination on the surface of the journals, which may have contributed to the early demise of the rod bearings. Also, everyone at the table agreed that polishing is done AFTER heat treating, not the other way around.

So, after polishing the crank and receiving my replacement rod bearings, I plastigaged the clearance, and it came out to about 0.003. That's pretty much the max allowable limit. Normally, new bearings would have a clearance of about 0.001, but the rod journals on my crank are ground 0.002 too far! (It was supposed to be a "10/10" regrind, but it ended up being closer to a "10/12" regrind.) What this means is that I may have to replace my rod bearings much more frequently than usual. Assuming I get the oil pressure stabilized, I can use that as a guide to tell me when it's time to replace the bearings. On that note, I also ordered a high-pressure oil pump regulator spring to see if that helps. During one of my tests, I replaced the original spring with a wooden dowel, just to make sure the oil pressure regulating piston wasn't getting stuck. When I did that, and spun up the oil pump with the electric drill, the pressure shot up to 70 psi, so I think I may be on the right track.

One other thing I noticed when cleaning up the engine was that the paint on the pushrod tubes was starting to flake off. I don't know if it was the paint, or the prep, or a different type of material, but in any case, I decided to powder coat them. I had my choice between red, yellow, or silver, so I chose silver. I'm very pleased with how they turned out.

Total Time: 26.5 hrs.