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Discussion Starter #1 (Edited)
Can I Heli-coil an Engine Mount Hole? Update: Problem Solved

OK guys, I need some help. I tried to replace my (perfectly good) donor engine mounts with some Poly Mounts today. The last bolt wouldn't torque down and the threads seemed stripped. The weird part is there were no threads on the bolt or other signs of a recent strip. I am wondering if I didn't have it tightened down enough when I go-carted in the Fall?!?:eek: Or if it was that way in the donor and I just didn't know it?

I guess at this point the cause doesn't really matter. I just need to fix it. So... my question is, can I use a heli-coil in the engine mount hole on the block? If so, is there a suggested size for this application? The bolt appears to be an M10 1.50. Can this be done with the engine in the car (supported from the top with a hoist)? I have never used a heli-coil... any tips?

As you can see, the stripped hole looks (and is) bigger. I can thread a bolt in by hand 3/4 of the way and then just pull it straight out! Yikes!

PLEASE tell me I can fix this without pulling the motor!!



In this pic, it looks to me like there is a broken heli-coil in the hole already. If so, can it be extracted or do I just drill it out?


Any help would be greatly appreciated, I am not at all happy with this set-back!

Thanks in advance!!

-Jon A.
 

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Hi Jon,
i can't see if that's a helicoil. You can install a 7/16 x 14 helicoil kit in the car. Done it many times before.
Is that an Explorer engine?
Good luck,
Mike
 

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Discussion Starter #3
Hi Mike,

Thanks for your response. The engine is from a '90 GT, it is not an Explorer. Does that make a difference in this situation?

-Jon
 

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Definitely 7/16, not metric. Maybe that was your problem since M10 bolts fit almost right in 7/16 holes. They just seem to strip out the threads before they get tight.
 

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Discussion Starter #5
Hi Joe,

I assumed they were M10 1.50 because that seemed like the closest match at the auto parts store. However, the bolts I was using were the same ones that came on the donor engine mounts so they probably are 7/16.

Do I drill out the existing hole (even if there is a broken helicoil in there) and simply stick a new helicoil in the hole is there more to it. (Can you tell I have never used a helicil???) :001_unsure::huh::D

-Jon
 

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Do I drill out the existing hole (even if there is a broken helicoil in there) and simply stick a new helicoil in the hole is there more to it. (Can you tell I have never used a helicil???) :001_unsure::huh::D
You can buy a Heli coil kit. It will come with instructions a drill bit , a tap and the Heli coil. They are in most autoparts stores and usually under $50.

Good luck and don't rush it.

Nc1mike
 

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Heli-coil

if in fact it already has a heli-coil--why can"t you back it out with an easy-out and reinsert a new heli-coil without having to drill and tap it?Matt
 

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The Earth is Heili Coiled to the Universe. Just follow the instructions and you are good to mount your motor mount.

Rick
 

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Discussion Starter #9 (Edited)
Update - Helicoil purchased

I went to the store and bought an OEM Fix-A-Thread #25608. (They didn't have the Helicoil brand in the right size. Here is the kit I bought:
http://greatnecksaw.com/product_info.php?pName=thread-rep-kit-296414&cName=service-tools-thread-repair

I will try to install it tomorrow. At the moment, the bolt is very loose in the un-installed helicoil... I assume when the coil is installed in the hole it tightens? Is that how it works?

I also confirmed that my donor bolts are 7/16 - 14 (by screwing it into the test plate at the auto parts store).

I might try to "easy-out" what appears to be the existing heli-coil in the hole... if that doesn't work, I guess I will just have to try to drill it out. I bought a new drill bit set because I need a 29/64" bit to drill the hole.

I hope this works!!

Thanks for the help, if anyone has any other suggestions, please let me know.

-Jon A.
 

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Jon what you have is the same as a heli coil just different name brand.
How they work. You drill the hole "over size" for the final thread. The hole gets drilled then tapped for the outside threads on the heli coil which now threads into the hole.
The inside threads of the heli coil reduce the repaired hole back down to the original thread size needed. How the repair works.
The install tool that comes with the kit is made so you can screw in the heli coil by way of locking tap on end. It engages the heli coil at the bottom. Even with the tool. coil screws in easy but does'nt screw out easy.
Eze out may work as will useing drill bits to drill a little of the insert out at a time.
Try to drill straight. Try to tap the threads straight.
Don't drill any further then exsisting hole.
Not a difficult repair. Take your time and sure you'll make out fine:)
 

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Discussion Starter #11 (Edited)
Update:

My father and I figured out the problem.... it turns out that the problem was that... I am an idiot! :blink:

The problem wasn't with the car, it was with me!! The hole wasn't stripped after-all, it was just a larger size than the other three. A new 7/16 - 14 fit well and torqued down to 35 lb ft. (The Chilton's Manual suggested 35 - 50 lb ft, not wanting to push my luck, I thought I would leave it at 35 lb ft rather than torque it further). I will make a note to check the bolt for tightness at my 100 mile safety review.

I don't really understand how this happened (probably because, as I mentioned above, I am an idiot). I used the same 4 bolts that held the donor engine mounts to the engine. They are all the same size. However, for some reason the hole nearest the oil filter was threaded bigger than the rest (7/16 - 14).

Thanks to everyone here for trying to help... it's not your fault that you couldn't help... "you can't fix stupid".:001_huh::yes: I would also like to thank my father for helping, offering advice and letting me swear at him for a few hours.

BTW - welcome my father to the site... he has been lurking for a while but I finally convinced him to become a member... so welcome "Oilpan" to the site.

Thanks again for all the help!

-Jon A.


PS

The biggest problem with this whole thing is that now Mark Ames has more fodder to use to make fun of me. :001_rolleyes:
 

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I'm confused...or you are. ALL the holes in the block for the motor mounts are 7/16-14. If you used something smaller in the other three holes, you'd better double check them.
 

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Discussion Starter #14
Joe,

I am confused as well. I am really not sure what the heck is going on. If you look at my first picture above you can see that the hole on the right (towards the rear of the car) is smaller than the hole on the left. Maybe the aft hole has a helicoil in it already.

-Jon
 

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The one that's already been repaired will LOOK bigger than the others, but chances are they are all 7/16. Unless, of course, somebody already buggered them up and just drilled them to the next size (1/2"). They are definitely not metric. The M10 vs 7/16 thing bites alot of people because they are so close.
 

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So Jon, I've been following this for its great entertainment value.
Seriously, you should do as Old Guy suggests, and make sure no metric bolts are mixed in there. They have to be all 7/16 x 14.

John S.

P.S. we're all idiots, so welcome to the club. How about buying a new mech. fuel pump and discovering that the bolts were just loosened on the old one. Gee, so that's where all the oil on the bottom of the oil pan was coming from!
 

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I stripped out a motor mount bolt hole and need a heli coil repair kit.
The link to the repair kit is a dead - not surprised as this thread is over 10 years old.
Can someone please confirm this is the correct kit i need to make the repair for 302 /351 SBF?
Thanks!
Tom
 

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My Heli-Coil experience. They work well.

However I don't believe you can use an easy out to remove one.

The Heli-Coil is slightly compressed as it is inserted into the threaded hole. It is held in place with this outward "spring" pressure.

As the bolt is tightened in the Heli-Coil it causes it to slightly expand outwards and puts the bolt tension load into the sides of the hole. That makes a Heli-Coil stronger than tapped threads, especially in cast iron, since a standard threaded hole puts the strain axially and pulls the threads out of the base material.

An easy out puts outward pressure on what ever it is attempting to remove to be able to grip the broken element, usually a hole drilled into a broken fastener, where the outward pressure is absorbed by the fastener being removed. That outward pressure from the easy out will likely just make the Heli-Coil grip tighter and not thread out of the hole.

To remove a Hili-Coil you need to get under the end of the "thread" with a pick and move it to the inside of the hole where it can be gripped with something like needle nose pliers and twisted out, putting an inward pull on the Hili-Coil thread.

JMHO Regards, Rick.
 
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