The Cessna 120-140 Association Forum

I'm ready to install a C85-14F on my 1948 140. TCDS requires a different engine mount, p/n 0451111 for this engine. I bought one from Univair, and the mount to firewall bolt attach openings are smaller than the original -12F engine mount, p/n 0451000, which uses NAS 145-15 bolts to attach it to the firewall. These "hex head" NAS bolts won't fit the new engine mount. I can't find anywhere in the 120/140 or 140A parts manuals that list any alternate bolts to attach the 0451111 mount to the firewall. The AN-5 is the correct size and fit, but I don't know what length to use.

Maybe I don't understand your question, but...

NAS145-15 bolts are not hex head. They are internal wrenching (socket head) bolts. The current part is an MS number, MS20005-6. Head diameter is about 0.526".

The only hex head bolt should be the top center one (AN5-6A).

The 140A parts catalog calls for the same hardware; I know of no other alternatives.

If you have the right bolts, then call Univair. Maybe they want you to use longer AN5 bolts that bear on the front of the tubes. Are the tubes 5/16" ID?

John-
I was incorrect in referring to the NAS bolts as hex-head. They are indeed internal wrenching bolts, an thus the problem; the head of these bolts won't fit inside the new engine mount openings. You are correct that this new mount is designed for longer AN5 bolts that bear on the front of the tubes. I just can't find any documentation for which length to use, or the approval basis. I picked up the new mount at the Univair facility in Denver, and showed them the problem. They have no idea.

n4688ukk wrote: ↑Fri Jul 15, 2022 11:54 amThey have no idea.

They have to. It's a PMA approved part. You just have to find the right person to ask.

Has anyone else on this forum used the Univair engine mount? Anyone have a parts catalog for a 150? Maybe they did things differently on the 150. AN5 bolts are not as strong as MS20005 bolts. There are 4 AN6 bolts holding the engine to the mount. Not sure AN5s would be an acceptable substitute.

[Edit]I found catalog and it shows 4 AN5 bolts, so the AN5s should be suitable for the 140 mount as well. After all, the 150 mount is carrying the nosewheel loads as well. It also calls for a special washer, S1450-5-18-063. Not sure where it goes or what it does. (Been a long time since I looked closely at a 150 engine mount.)

Does the new mount have a washer welded to the bottom of each tube the bolt is supposed to go in, or is it just a straight tube? (Can you post a picture?)

Is the ID of the tube a good fit on the 5/16" bolt? If so, you might be able to use MS20005 bolts and MS20002-C5 washers. You'll have to measure the depth of the tube and add that to the length of the original. NAS bolts are measured in shank length whereas MS bolts are measured in grip length, so you'll have to do some conversions.

6643 wrote: ↑Fri Jul 15, 2022 9:25 pm [Edit]I found catalog and it shows 4 AN5 bolts, so the AN5s should be suitable for the 140 mount as well. After all, the 150 mount is carrying the nosewheel loads as well. It also calls for a special washer, S1450-5-18-063. Not sure where it goes or what it does. (Been a long time since I looked closely at a 150 engine mount.)

Some internal wrenching bolts have a radius on the outside diameter where the head starts and need the special washer to fit into that radius.
Spruce has them listed as MS20002C5, the picture shows the radius.

Rick

8342 wrote: ↑Sat Jul 16, 2022 5:16 amSome internal wrenching bolts have a radius on the outside diameter where the head starts and need the special washer to fit into that radius.

Actually, all MS and NAS internal wrenching bolts require the special washer. Many applications do not call for a washer under the head, and the part is radiused to fit, as is the case with the original engine mounts, and, e.g., the gear legs where the axles attach.

The Cessna S1450-5-18-063 washer applies to the AN5 installation and is likely for stress distribution.