kens_cockpit
Well Known Member
I have attached some pictures of the top left engine mount hole.
I aligned the engine mount using some correctly sized pins in 3 of the holes and drilled the first hole using the mount as a drill guide then put a bolt in that hole and moved to the next one until all four were done. It appears I drilled this hole first or last and the engine mount didn?t line up with the predrilled hole. Anyway the cause of the problem doesn?t matter except to avoid it next time!
The question is what do I do about this. I see a few options:
1. Leave it. I think this is not good. It is one of only 4 attachment points for the weight, power and vibration of the engine. The ability of the hole to work as it was designed seems to me to have been severely compromised. I see the potential for the edges of the original hole to scratch the bolt and lead to cracking. That seems far too risky to me.
2. This is my preferred option if it will be safe and satisfactory. Drill out the rivets holding the WD-802-L engine mount bracket angle and the F-801J filler plate to the firewall and longeron and install new WD-802-L and F-801J. This would leave the hole in the firewall only out of shape. The engine mount sits directly on this and that may mean there is some risk of scratching the engine mount and causing cracks there in the future. However I could deburr and smooth the sharp points on that hole which I anticipate would alleviate that problem. It would then mean that the stainless steel skin would not be providing support to the bolt all the way around but I expect the design is for the engine mount bracket angle and filler plate to do that and not the firewall itself. Also, drilling out the rivets will leave slightly enlarged holes in the firewall (though I would think not as bad as usual as it is stainless steel not aluminum). If this was a problem then perhaps some extra rivets could be installed to create extra strength. I do not think the extra rivets would be required but I will install them if you would advise that course.
3. Some other repair to fill the original hole and fill to the edge of the drilled hole. I can?t see how this could be done satisfactorily.
4. Completely rebuild the firewall and engine mount brackets. I think this would be overkill.
5. Something else you can advise me about.
Can I please have your thoughts?
Thanks