Hello all,

 Does it matter if the bolts that attach the engine mount to the fuselage go from inside the fuselage out or  from the engine mount through the firewall into the plane?

 I have the Viking 130 mount on a 650. I attached the mount temporarily today to help move from the basement to the garage,  The Viking mount needs about a 2 1/2 inch bolt.

  With the 10 degree angle on the front of the fuselage mount brackets I don't see how I'd be able to get a long bolt to go from inside out.  The AN6-7A in the Zenith plans work ok that way but they aren't nearly long enough.

What do you think?

Thanks - Jim

Views: 536

Reply to This

Replies to This Discussion

Not sure I understand the issue.  I don't recall anything preventing a long bolt going from inside.  I will look tomorrow to refresh my memory.

I did mine with the bolts protruding forward from the inside, through the firewall. In other words, with the threads forward of the firewall.  If it were the other way around, the nuts would be very difficult to tighten and inspect.

I recall it being a tight fit (on an XL, with a 13 degree rake), but doable. 

- Pat

My 601 came with the bolts attached to the motor mount with the treads facing forward. - no issue there and it passed the DAR inspection. 

Come to think of it, I believe mine did too.  But now that I am thinking about it, I think those were superceded or perhaps it occurred when I went with 650 canopy, but in any case I got new ones and used bolts but I still do not recall there being an issue with them having heads on inside and threads forward of firewall.

Thanks guys. Viking is sending me some with my updated ECU and flywheel drive plate. I'll try to get them to face out like normal. Patrick - good point about inspection too.

According to the FAA acceptable methods ,techniques and practices it is preferred to torque the nut if possible but torquing the bolt is not prohibited. Page 7-298 for those interested.

Glenn Davis 


Hey Glenn,

  Did you use bolts from Viking? If not, what did you use?  Are they facing out (threads on the engine side of the firewall)?

Thanks - Jim

No, My bolt heads are FF. I know I'm a disappointment to the Davis name but I could not get the bolts to go thru like you guys did short of beating the hell out of it or elongating the hole .I researched it and put em in back asswards, I can't remember if Viking supplied them or not but I don't think so.

Glenn Davis


I think I'll be doing the same as you - Davis's Unite :-)

Do you mind sharing what the immovable object was that was in the way?  Some times just a slight change in assembly order can make all the difference in the world.

Sure, it's the engine mount brackets themselves. The front edge is canted back about 10 degrees I think. There just isn't room to get a long bolt through from the inside. I'll take a pick later today.

Thanks Jim,

I must have slightly elongated the hole but don't remember for sure.  I do for sure remember that first ones that came with kit, bolt was welded in place.  For only 10 degrees, the elongation required would not be very much.


New from Zenith:

Zenith Planes For Sale 

Classified listing for buying or selling your Zenith building or flying related stuff...

Custom Instrument Panels
for your Zenith

Custom instrument panels are now available directly from Zenith Aircraft Company exclusively for Zenith builders and owners. Pre-cut panel, power distribution panel, Approach Fast Stack harnesses, Dynon and Garmin avionics, and more.

Custom Upholstery Kits for your Zenith Aircraft:

Zenith Vinyl Upholstery Kits

Zenith Apparel from EAA:

Zenair Floats

Flying On Your Own Wings:
A Complete Guide to Understanding Light Airplane Design, by Chris Heintz

Builder & Pilot Supplies:

How to videos from HomebuiltHELP.com

Developed specifically for Zenith builders (by a builder) these videos on DVD are a great help in building your own kit plane by providing practical hands-on construction information. Visit HomebuiltHelp.com for the latest DVD titles.

Aircraft Insurance:


West Coast USA:

Pro Builder Assistance:


Transition training:

Golden Eagle Aviation

Pianosa Flying Farm

Aircraft Spruce & Specialty for all your building and pilot supplies!

© 2020   Created by Zenith.Aero.   Powered by

Badges  |  Report an Issue  |  Terms of Service