Stripped threads in engine block

[docs302]

I was installing the Watson solid motor mounts and damaged 3 of 4 bolt holes in the right side block. Since the mount was so thin I went out and bought shorter flange bolts (3/4 x 1) but I think they were too short. I probably should not have used the impact gun to get them started as I went too far.
The logical answer is to tap new threads. But I used three 1.25" inch long bolts on the other side that worked fine. Do I try longer bolts to grab up higher in the hole or is that going to be too risky for strength? If the answer is tap new threads, any advice? I tapped threads in an old Subaru many years ago when I stripped a spark plug hole and I actually made it work. Before I go out and get the tap and die kit I will wait for some responses.

Thanks

 

[ArizonaBOSS]

I am always super paranoid about this considering it's an aluminum block. Neverrrrrrrrr use an impact to put stuff IN to the block.

What I would try first is to carefully clean out the existing/remaining threads with a tap, and then see if you can use the more of the 1.25" bolts you used on the other side and see where they are engaging. You can buy a single tap and driver at ACE or other local hardware stores, typically.

 

[docs302]

Neverrrrrrrrr use an impact to put stuff IN to the block.

I'm kicking myself because I knew the gun was a bad idea.....laziness. The more I think about it the more I am convinced a 1/2" longer bolt with some Loctite should grab and stay put. Lesson learned.

 

[docs302]

ArizonaBoss, while I am at it. I added a Setrab 925 cooler and Moroso road race pan. How much oil should I be looking at now to fill it?

 

[ArizonaBOSS]

11-12 quarts.

 

[scmscout]

Just be careful when starting the tap, make sure it is straight and square to the existing hole and is not starting to cut new threads, if it does you will cut the remaining threads and you will have nothing left. I would suggest a 4 flute bottom tap.

 

[docs302]

11-12 quarts.

Wow....not a cheap fill.

Just be careful when starting the tap, make sure it is straight and square to the existing hole and is not starting to cut new threads, if it does you will cut the remaining threads and you will have nothing left. I would suggest a 4 flute bottom tap

Thanks for the information. I am going to try a longer bolt first and if it grabs well I will leave it alone. The tap is last resort. Can't screw this up.

 

[RES_22]

Got enough meat for a heli-coil?

Always works if there’s enough left (diametrally) to anchor the insert.

Good luck.

 

[TMSBOSS]

If drilling for the heli-coil, be sure you don’t drill too deep.
If you have room to put in stud in the original hole. You may get an additional thread or two engaging with the stud. Bolts will either bottom out or leave a thread or two not used.
Good luck with the repair.

 

[docs302]

Update:

The longer bolts did the trick. I wasn't sure anything was biting but eventually I felt it snug up and I quit while I was ahead. With a little Loctite I think I will be ok but I will check after driving a bit to make sure the extra vibration doesn't work them loose. Thanks for the support.