broken motor mount

[mrbeggins]

Can anyone tell me if it is possible to weld a broken motor mount (the threaded mounting holes on the block itself). I am aware that it is cast. If it was welded, would it stand up ? Thanks guys.

[Bnine]

Essentially, no.

If they are stripped, just helicoil them and call it good. Welding to cast is a really involved process, and definately not a good idea on motor mounts.

[cLAY]

Often when the boss breaks there is nothing left to heli coil. It can be welded but would need to been done professionally and the engine would have to be pulled to do it.

[Bnine]

Even in that case I would weld a peice of tapped tubing into what was left of the boss, rather then weld the mount directly to the block.

Still not something I would want to do, and definately agree with Clay, the motor has to come out at that point. There is no other way to heat wrap it properly, which is one of the processes to welding cast.

[mrbeggins]

Ok, thanks for the replies. I have the motor out already and is cleaned up. all three bosses are broken off, however, there is still some threads left in the remainder, - enough to screw in studs. From there a guy can hopefully weld the studs in place, slide a new prefab boss over top and weld the whole kit and kaboodle together. do you think this will work?

[Bnine]

It need a lot of preheat, hi nickle rod, stress releived, and wrapped to cool as slow as possible.

Even with all that, and a guy that is a good welder, it can still crack and fail easily.

You need a welder that is confident welding cast.

I have buddies that are good b pressure, and high end tig welders, none of them are comfortable with cast. Its such a crap shoot.

Good luck. Hopefully you get it worked out.

[cLAY]

Not sure what the setup is like on a yj. Could the studs just be welded in and then the mount bolted to it?

You are going to have to talk to a welding shop about this. We're pretty much just making blind guesses here.

[gsxtacy]

it is a crap shoot welding cast...

i work in the NDT side of welding, which means, i test all the stuff they put out.

essentially, when you have a cast material(engine block), as opposed to the forged material (studs), they cool under different pressures, and are both formed differently, creating different melting points for the parent material.  different grain structures also inhibits welding forged -> cast properly.  it can be done, but my best guess would be not to do it at all.


it's brutal to say the least.

even the best welder, because of all the different zones of the weld, would have his bead brake within about 20 000 km just because of the vibrations an inline engine puts out. you would most likely see Heat Affected Zone (HAZ [1-15 mm from actual bead, both sides]) cracking and/or actual crater (stop/start) and longitudinal or transverse (straight up and down or across the bead) cracking depending on the weld method and type of consumables used. as illustrated in the picture below (bear with me =3). you may also find, that if welded and cooled incorrectly, the parent material will also crack and/or shear completely off... it's no good having a block that is broken. either get a professional shop to do it (Nat'l 4x4 may be able to recommend someone) or leave it be.



disreguard #'s 1-> 4,
5 is the actual weld puddle,
6 is the completed bead,
7 is the parent material

[Gearhead]

I say toss it , get another , end of story.










Note to self .........    buy M.O.R.E.  bomb proof engine mount brackets.

[mrbeggins]

Ok, thanks for the info guys. I think I'll just get rid of it and start over. This all began as a 2.5L to 4.0L swap with the engine coming out of a doner vehicle. We did not notice until we were pulling the 4.0L out that the bosses for the engine mount on the block, were broken.  Thought we had a good 4.0L HO, tranny and transfer case ready to go in, - except for this setback. Oh well, - its only money....&%$#@*^!!!

[Gearhead]

Part out that engine , it's possible it has .......

A good useable cylinder head
A good useable crankshaft
The manifolds
The accessories n' stuff

What would I do ?

1. Find another block , or core engine.
2. Have all of the necessary machining done
3. Assemble another engine , better than what you have now.
4. Put More bomb proof engine mount brackets on the replacement eng.

Some times "junkyard / salvage " builds turn out this way , or you encounter glitches during the build , turn it in to something positive.
Yes , it may cost more than initially planned for or may take longer.

I did a stroker build last year  , it started out bad with some worthless stuff I bought before I had put together a solid plan   but turned out to be a success at the end of it all . Too bad it's in between a pair of  rusty frame rails . upside is , Pffff ,  good  used frames can be found.