Damaged 8mm bolt hole... Best repair?

[Noozer]

I had a bolt break off in my aluminum engine block. I've been able to get the broken piece out of the block, but the threads were damaged. Now I need to repair this...

The original bolt was an M8x1.25x100mm of #8 hardness. If I put a new bolt into the hole, it does grab but is VERY loose and not suitable to hold it's braket in place.

I was hoping to find an M9x1.25x100mm bolt, but no luck. I then tried to locate an 11/32"x4" bolt and again, no luck.

So now I figure I can drill this hole out a bit and cut threads for a

3/8"x4" bolt...

Does this sound reasonable?

My biggest issue is clearance. I had to use a 90' drill to get the broken bolt out. There is almost no visibility to see if the hole is straight. The bracket that mounts here does not have any critical tolerances.

Suggestions?

[Joseph Meehan]

[David Martel]

Noozer,

Your plan or Mr Meehan's helicoil will both work. My objection to your plan is your intent to introduce an SAE bolt into a metric engine. The next person to work on the engine will be using metric tools on this bolt. With the poor location the helicoil may be the better bet.

Dave M.

[Jeff Wisnia]

If it's that hard to access you might have a heck of a time trying to properly install a helicoil insert.

If the bracket is not something you anticipate having to remove and replace often I'd give a try to using JB Weld to "glue" your new M8x1.25 bolt into that buggered up hole.

Use a Q-tip and solvent to clean out the hole and the new bolt threads as best as you can, then slap on some JB weld and drive the bolt in as tight as you dare to without stripping the hole.

That's worked for me and it might for you too, and if it doesn't, you can start from scratch again.

HTH,

Jeff

[Don Young]

I often use Jeff's idea but use a separate stud and nut. After a good cleaning, smear the hole and stud with JB Weld or similar epoxy and screw the stud in until it bottoms out. Let it set up for 24 hours, install washers as desired, install nut and tighten. It makes a stronger and removeable connection.

Don Young

[~^Johnny^~]

LOL!

Why not just arc weld the damn thing, and be done with it?

[Noozer]

It's an aluminum block. Don't think it would weld too well...

I ended up drilling it out for a 3/8-16 bolt and it worked out great

[J. Clarke]

If drilling and tapping was an option then the right fix would have been to put in a Helicoil.