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Stripped Engine Mount Bolts


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#1 projectnut OFFLINE  

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Posted July 06, 2012 - 07:46 AM

Last week I using my Case 224 at our cottage to haul a couple loads of wood when I noticed the engine seemed to torque on its mounts just a little under a load. After finishing the job I did an inspection and found both bolts on the right side engine mount plate (Kohler K series 14hp) were damaged. The rear one must have been stripped for some time since the top of the plate was worn and the bolt hole was oversized.

I removed the engine, welded up and rebored the damaged plate, and now it's time to repair the threads in the case. At the time I should have taken a close look at the case to see how much room was available for either a helicoil style repair or a thread insert. I'm leaning toward drilling and tapping for an insert rather than the helicoil. The insert requires a 9/16 - 12 tapped hole and the helicoil requirs a .397 drilled hole before tapping with the special tap.

Has anyone made this type of repair, and if so which route did you take? As I said earlier I'm leaning toward the insert but since the tractor isn't here I'm not sure there's enough room in the case to drill and tap that large a hole and still have sufficient strength. Another complication is that someone has already tried to helicoil the front mounting hole on the same side. They did a poor job and the coil isn't flush with the bottom of the case. At best I'll have to remove and replace it.

Thanks, projectnut

#2 JDBrian OFFLINE  

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Posted July 06, 2012 - 03:03 PM

I have no idea what it looks like so this may not work but would it be possible to simply go to a slightly larger bolt and drill/ re tap the holes. If they are 3/8 you could go out to 7/16 and wouldn't have to remove much material at all. You wouldn't have to fuss with a helicoil and worry about getting the coil in flush etc.

#3 MH81 ONLINE  

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Posted July 06, 2012 - 05:53 PM

Is it possible to go up one size as Brian suggests and then put a locker nut on top to help it out?

#4 projectnut OFFLINE  

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Posted July 06, 2012 - 08:22 PM

It might be possible to go up 1 size but the mounts are blind holes so there's no possibility of locking nuts. In this case the bolts are flat heads that come up from the bottom . They secure 2 plates to the bottom of the engine. The plates in turn have rubber mounts that secure them to the frame. Going 1 size up would make the external diameter of the tapped hole .437. The threaded insert would have an external diameter of .562

The other thought is that the original holes were drilled and tapped into an aluminum oil pan. Since they failed once due to vibration I would think it could happen again. The thread inserts are hardened steel so they are less likely to strip out. They're also self locking so they won't vibrate out of the pan. Keep in mind whatever size I go to I'll have to find the appropriate flat head bolts to keep as close to the riginal mounting system as possible

#5 olcowhand ONLINE  

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Posted July 06, 2012 - 08:26 PM

I believe I had that type oil pan off an engine. I'll go look & snap some pics for you to see what you have to work with. Be back in a few minutes!

#6 olcowhand ONLINE  

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Posted July 06, 2012 - 08:39 PM

PN....good to hear from you again. You needn't be a stranger ya know!
Yours I think has the flat oil pan, where this one has the sump, but they are much the same in the blind hole areas. From the outside, it appears they have a wide area of material for tapping larger, but inside they don't have all that much material. Here's a couple pics to give you an idea. In the 2nd pic, I am pointing to the area the threads are under. I think enough to tap for 7/16 threads, but I'd not dare go 9/16 myself.
DSC00104.JPG DSC00105.JPG

#7 CASENUT OFFLINE  

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Posted July 07, 2012 - 07:10 AM

I hope this is what you're talkin about I've done this to 2 seperate motors...and the process works great...GL
the pics do not appear in order, but take a look at them all and you'll know how to go about this process...
http://s312.photobuc...licoil project/
  • bgkid2966 said thank you

#8 bgkid2966 OFFLINE  

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Posted July 07, 2012 - 08:32 AM

Helicoils are great for this type of repair. Just be 100% sure to not drill through. Measure hole depth and put a tape stripe on the drill bit to mark the stop point. Good luck with the repair.


Geno

#9 projectnut OFFLINE  

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Posted July 07, 2012 - 08:34 AM

Thanks Olcowhand & NutCASE. It looks like the Helicoil insert is the only way to go. I've used them in the past but generally prefer the inserts whenever possible. In this case It doesn't look like there's much choice.

Thanks again projectnut

#10 CASENUT OFFLINE  

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Posted July 07, 2012 - 09:02 AM

Thanks Olcowhand & NutCASE. It looks like the Helicoil insert is the only way to go. I've used them in the past but generally prefer the inserts whenever possible. In this case It doesn't look like there's much choice.

Thanks again projectnut


There may be another 'choice' but the helicoil for this application works great and is rather inexpensive...The previous poster said use a piece of tape, you should use a drill stop which is a ring with an allen screw in it so you cannot drill to deep...but measure so you know precisely...GL

Edited by NutCASE, July 07, 2012 - 09:03 AM.


#11 projectnut OFFLINE  

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Posted July 13, 2012 - 06:47 AM

Thanks again everyone. I got a little time yesterday to repair the engine mount threaded holes and reassemble everything. I was shocked how easy the project turned out. I was expecting it to be much more difficult. The last time I tried to use helicoils I was squeezed inside a packaging machine, standing on my head trying to drill a hole in 1 1/2" aluminum plate with a drill almost as large as the opening I was crammed into. This time everything was accessible standing upright in front of the work bench. What a treat.

Everything's back together and better than ever. While I had the engine out I found a few other bolts that had loosened over the years so I replaced a few and tightened a few more. No shakes no rattles, no unusual noises. The thing now runs better and quieter than it has since I started using it.

Along the way I also converted the home made weight bracket to accept a winch. Now I can easily drag brush up the hill without having to continually perform death defying acts.

Thanks, projectnut
  • CASENUT said thank you




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