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Engine mount bolt/cotter pin

Dgamble

Well Known Member
When torqued to 160 in-lbs, the top engine bolts are far enough into the castellated nuts that it seems as if the cotter pin doesn't have a full grip:



Considering that the cotter pin will still keep the nut on the bolt, should I leave it as-is, or try to find a washer to shorten up the bolt a little bit?
 
Washers

Yes, thick or thin washers are used to place the castle nut in the right position to accept the cotter pin.
 
A washer certainly would help here in adding more meat for the cotter pin to be surrounded by. For my own peace of mind if I had this issue, I would add one and redo with a new cotter pin.
 
I had this exact problem. After a gentle suggestion by my DAR, a washer of the appropriate size centered the hole in the nut.
-Bruce
 
What Anthony said.

Also, for those folks who are reading that might consider showing their plane at Oshkosh....the Judges will absolutely mark down if that castle nut was displayed same as in the pic.



Considering that the cotter pin will still keep the nut on the bolt, should I leave it as-is, or try to find a washer to shorten up the bolt a little bit?
 
should I leave it as-is, or try to find a washer to shorten up the bolt a little bit?

Dave- That looks like the top engine mount and my iteration of plans call for a AN960-616 washer to back the nut on the top two mounts (no washer is called out on the bottom two mounts). I hung my engine last night... Here's mine without the cotter pin installed torqued to 160 in/lbs and even with the washer it looks like it could still use another.

156cw38.jpg
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The same is true for the other top mount. The bottom mounts appear to be fine. Is it acceptable to stack two washers there behind the nut? Or do you guys recommend putting the additional waster on the bolt head side?

Thanks!
 
Last edited:
I ordered some -616 and 616L washers last night. The thin L washers should allow a little fine-tuning if required.

Dave- That looks like the top engine mount and my iteration of plans call for a AN960-616 washer to back the nut on the top two mounts (no washer is called out on the bottom two mounts). I hung my engine last night... Here's mine without the cotter pin installed torqued to 160 in/lbs and even with the washer it looks like it could still use another.
 
Found a 2009 picture - -

I have washers on mine. Did not go back and look at instructions, but likely what was called for.

John Bender
354.4 hours
 
It took both of the supplied washers to get one of the nuts far enough out. There're only $.03 each - no big deal even with the $.74 shipping.
 
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