SonexBuilders.net

Opinions please.
I, in a moment of stupidity, mistakenly torqued my three camshaft bolts to 40 ft. lbs. instead of the required 20 ft. lbs.. I am a retired A&P with many past years of using a torque wrench and know the feel of threads being damaged while tightening or loosening and did not detect any thread damage being done. I first slowly tightened to 20 ft. lbs. and then in my moment of stupidity cranked up 40 ft. lbs. and tightened them slowly again. My feeling now is that I am better off to let the sleeping dog lie than I am with loosening the bolts and retightening them to the required 20 ft. lbs..
Suggestion for all builders........when you start feeling tired stop your work, put down your tools, turn off the light and roll shut your hangar door.
Surfly

I am not an engineer. But I do know that over torquing puts stress other than on the threads. If it were my engine I would replace the bolts and inspect the threads on the cam shaft. I would be thinking about those bolts every time I fly. Just my two cents.

I am an engineer and even I would suggest replacing the bolts. There is very little chance you damaged the cam gear or camshaft but you could have exceeded the yield stress of the bolt and not know it. These bolts aren't in an area where if they fail you can just drill them out and replace them. A failure of the cam bolts will end up in a very bad day or at least a very expensive one. The cost of three bolts is meaningless compared to the potential impact of them failing. If you are posting it here I suspect you already know what the right thing to do is.

Keith
#554

I am a retired service engineer for medical equipment. Please change the bolts. they are not expensive comapared to a lawyers fee when the overstressed ones fracture. maybe even pull the cam and have the threats inspected by someone capable of doing so. We all learn from experience, good and bad. No one needs any experience from something as simple as foresight with bolts and threads. you know what to do. Just belly up and do it! I would in a heartbeat if I did overtorque these bolts. the same goes for conecting rod bolts. Please let us know what you do, and find out about the threads. anyway, Merry Christmas, and have a safe and happy New Yesr. :)

I'm not so sure about leaving the sleeping dog lay. Those bolts do stretch and are now in a stressed situation they were not designed to be in. So my suggestion would be to remove the bolts and replace with NEW ones and torque to the 20 ft lbs.

AL Roberts

Thanks to all. New bolts will be installed at the proper torque setting.
Surfly