Cast Iron Question.

[mcostello]

did not want to hijack the other thread so here goes.
I have a minivan that has a product history of manifolds warping and breaking the exhaust studs off in the head and thereby causing a leak. Have to pull engine out to get to all the broken bits because I could not remove a cam cover due to more rusted bolts. I have Tigged all the bolts out 6-7 of them on both heads. Question is after I mill the manifolds back to flat and install new studs, could the manifolds warp again necessating another repair? 4 bolts missing on one head with only 2 bolts holding head t engine. Got 135,000 out of it so far. Thinking about going to use Aircraft studs to gain strength. Does that sound OK? What do you think?

[SidecarFlip]

I'd like to know what 'Tigged' the bolts out means....

The proper way to remove a broken exhaust stud in any head is to drill the stud out with a drill bit slightly smaller than the minor diameter of the thread. The chase the threads out with an appropriate sized tap or Hansen Spline Drive thread chaser.

Having said that, we use a die reclaim drill, commonly call a Hi-Rock. I've drilled many exhaust studs on Caterpillar 3406 Diesels and broken head bolts as well and never had a failure.

I believe you'll find that there isn't going to be enough 'meat' to mill the manifold. Modern castings aren't like old ones where the casting was made in a sand mold with plenty of draft. New castings are made with no excess.

[SAWDADDY]

if it warped once, bad enough to break studs, milling it (makes it thinner on the crown of the bend) won't make it warp less in the future and now it won't be an even thickness. It might be expensive, but considering how much time you have into it I would look for quality stainless headers. Believe it or not companies like Borla sometimes have applications for minivans & econo-boxes. If it has a history & reputation for doing this it is even more likely someone makes it. On an upside for the cost a good quality cat-forward with headers may get you between 1 -5 MPG improvement. I put a Calmini header & cat back on a Geo Tracker 4x4 and went from 24 to 31 MPG. A header from a really good mfg will probably have a 5/16 to 3/8 flange and never give you another problem.

as for studs/bolts, the best you can get for header manifold mounting are ARP and they will have fasteners for your exact application.

[Rocky D]

I'd like to know what 'Tigged' the bolts out means....

This is a small example of Tigging out a broken tap, but studs would be the same procedure. This is a 6-32 tap. I use hastelloy for the build up of the L





Sorry about the oversized pics.

[mcostello]

Just to let the new guys know what can be done with a Tig machine, I cannot yet run a good looking bead, need more seat time, but I sure can Tig out bolts. Saved me from spending lots of time drilling and retapping.

[Roger]

I'm guessing localized heating of broken stud from TIG welding cause expanding and contraction of stud to ease removal.

[mcostello]

Yes the extreme heat seems to do it, also you get a handle or a handy nut that provides nonslip grip. One of the studs required 4-5 attempts to remove it. Drilling was an option, drilling off center was a possibility and this was an aluminum head. If the drill would have gone off center it would have positively dove to the aluminum. Aluminum was a good heat sink cooling parts to the touch in about a minute. No problem with weld sticking where not wanted as the head was not cleaned, also could not get the stud very clean. Got it out and that is what counts.

[SidecarFlip]

I'm not too old to learn something, I've just always used the mechanical means.

Of course I routinely pull pressed in cylinder liners using the vertical weld bead/shrinkage method. Beats hydraulic pullers. One out with the stick welder, one in with the freezer.

[mcostello]

There IS a reason we buy all these tools, just most wives don't seem to understand. The more of them you have the more you can do and save.

[drujinin]

Tractor/Machinery repair/restore guys use a Mig by placing an appropriate washer on the broken stud, weld it on, then weld a nut to the washer. I've done it with a Stick Welder in a pinch! Never thought to use a Tig. Will have to keep it in mind
Thanks! I learned something new today too!
drujinin

[Blacksmith]

This is a good place to follow up on the fastener thread. The rule of thumb where I work is to tighten a fastener to 70-80% of it's yeild strenght (breaking point) to ensure the nut or bolt doesn't loosen due to vibration. This is the target for most designers when specifying a torque. Using a higher strength fastener may result in crushing the materials being fastened before fastener is in enough tension to lock the threads. Best advice was to install headers with ARP fasteners.

[Hotfoot]

Tractor/Machinery repair/restore guys use a Mig by placing an appropriate washer on the broken stud, weld it on, then weld a nut to the washer. I've done it with a Stick Welder in a pinch! Never thought to use a Tig. Will have to keep it in mind
Thanks! I learned something new today too!
drujinin

...and I with a MIG...works fast, sanitary...but I put the washer, then hold the nut with Needle Nose Pliers, and hit it all in one step...fill the nut with weld.