Rough running O300A

[bagarre]

Bruce, that was so unkind ,a shaky Lycoming ?? .Never, they only more around to stop the dust settling.

I got a kick out of that one too!

It's a feature. It helps to shake the rust off the cam lobes.

[gsflyr]

Thanks for suggestions, and the humor...
Still haven't eliminated issue. Getting ready to run a dynamic balance test, but in the mean time does anyone know the engine mount bolt torque value for my application? O300A on '52 B model?

Gary

[Bruce Fenstermacher]

There is no engine bolt mount torque. The '62 and Prior Service Manual states ond 12-32 para 12-66 note:

Screen Shot 2017-01-05 at 12.14.13 PM.png (48.44 KiB) Viewed 14401 times

170s serial 19200 and use the later technique as there is a rubber bushing and the bolt is not clamping metal together as described in the first instance.

170s serials prior to 19200 do not have a bushing and then standard torque would be appropriate. In my opinion in this case standard torque is not necessary so long as it is tight. The bolt is in shear with the same strength either way.

[n2582d]

Gary,
I found this in the '69-76 C-172 service manual:

Figure 11A-1, Click to Enlarge

[Bruce Fenstermacher]

The fire wall bolt illustration is that found prior to serial 19200. When you clamp down on the nut you are squeezing metal from the bolt heat to the nut. In these cases the reference I called out and Gary posted agree. 160-190 in lb is standard torque for the AN6 bolt found there. In the case of the bushing from the motor to the motor mount, if Im not mistaken, there is a metal tube thru the rubber bushing and so you would be clamping metal from the head to the nut of the bolt. Again standard torque is called for.

The motor mount to firewall 19200 and later however has a conical bushing (#7). There is no continuous metal to metal contact from bolt heat to nut.

Screen Shot 2017-01-05 at 2.05.13 PM.png (43.48 KiB) Viewed 14390 times

In this case standard torque would likely over squeeze the cone bushing and one would use the tightening technique described in my reference.

This detail is for others, I'm sure Gary knows this. Thanks for the other reference Gary. It makes clear the difference between the firewall bolt and the motor to motor mount bushing not specifically referenced in my reference. Both references tell the whole story and neither by themselves clearly do.

[mongo2]

Just a question, as I have a slight vibration:
In SNL 3-23-54, if the lower pic is of the 170, and the view says looking aft from prop, wouldn't the clock angle be about 1 pm \7pm ? as viewed facing the prop from the front , looking aft?

Thank you.

[n2582d]

Rick,
Both the top and bottom illustration of "sheet 1" refer to the C-170. The next page -- "sheet 2" -- of the SNL was not included as it applies to the C-180. On sheet 1 the top illustration is showing the engine flange while the bottom illustration is showing the propeller hub. The diagram doesn't make sense to me because it appears that the bottom illustration of the prop hub is showing the "former" position if viewed from the front. Disregard the bottom illustration. Just look at the top illustration of the crankshaft flange when you install your prop at the 11 and 5 o'clock position as viewed from the front looking aft.

[mongo2]

Gary,

Thanks for the clarification.. makes perfect sense.. I''ll check it out. If it is currently correct at 11/5, then I'll swap ends to see if that changes anything..

Regards,
Rick