CO in the cockpit

[Dan Thomas]

Right. But the OP said the clamp fasteners were ¼-20. Thanks for posting the correct torque table for the ⁵/¹⁶-18 nuts.

If the OP had quarter-inch coarse-thread bolts in his clamps, someone has installed the wrong hardware, and they might have drilled out the clamps' bolt holes as well, weakening them.

 

[Skyrys62]

..

Well, technically, I'm not the OP, but I did say they were 1/4...which was confusion in communication on our part. They are ANC3-4A bolts. Which are not drilled for cotter pins as indicated in what Dan posted.


Not sure if it makes any difference or not, but it was highlighted.


aside from that..

Went with the 90in lbs, followed by run up, recheck, then test flight. Rechecked the torques after cool down. Which I now testify can be done with only the top cowling removed. Takes some contortion and a couple different configurations of extensions, but it has officially been done.

Zero reading on CO detector and nothing has fallen off so I'm happy in that regard. I'll be keeping an eye on the gaskets for any leakage.

One thing that keeps swirling around in my head, is why only 40in lbs to install studs, but double or more for the nuts...which also applies to other areas. One being the dual magneto. It has the same 5/16x18 studs, but is torqued to 204in lbs?
Maybe less heat/expansion than the exhaust?

 

[Dan Thomas]

..
One thing that keeps swirling around in my head, is why only 40in lbs to install studs, but double or more for the nuts...which also applies to other areas. One being the dual magneto. It has the same 5/16x18 studs, but is torqued to 204in lbs?
Maybe less heat/expansion than the exhaust?

The stud needs to be a force-fit in the head so the nuts don't drag it out. The torque on the nut is a result of the friction between it and the lockwasher and flange, and much less so on the stud threads. If the nut's friction on the stud thread was higher than the stud's friction in the head, it would indeed come loose, but it's not. We do, however, sometimes see nuts rusted to the stud, and the stud comes out with the nut. That's why the correct (and more expensive) nut for that is a silver-plated nut that really resists corrosion. Ordinary coarse-thread AN nuts will eventually rust to that stud and could cost a whole lot more in the end than the right nut would.