stripped exhaust manifold bolt hole ?

[Highbanked Hauler]

  What is standard repair procedure ? How do you get a broken stud out ? Can you use a helicoil  or is it a machine shop repair ?

[RallyeMike]

I have drilled out a broken stud, easy-outed the remains, and chased the threads successfully. I have also broken off the easy-out which made things worse. You have to be careful. These studs are often very stubborn.

They are pretty tough to access with the right tools.... or impossible depending on which one it is. You'd be super lucky to be able to do it in the car. Taking the head off and a trip to the machine shop is a good bet.

[Highbanked Hauler]

 That is what I figured, tapping it out was wishful thinking but I had to ask.

[Bronzedodge]

Is the broken stud flush or below the surface of the head?  There's a few ways that can work w/ planning and patience.  First, center punch the center of the broken stud.  This can be tricky to do.  You can buy left hand drill bits online, Eastwood, maybe Harbor Freight has them.  A reversing drill is necessary to use them.  Start with 3/16" and work your way up to 9/32"  Then you can attempt an Easy-Out or other bolt extractor.  Warming with a propane or MAPP gas torch can help a lot.  Use a small wrench for the easy out and know your own strength - stop before you twist it off.

If the broken stud is above the surface, weld a 3/8" nut to the end.  You'll need good penetration, correct wire speed, etc.  I've centered 3/8" nuts over flush broken studs and have been lucky enough to get a good weld & they come out.

Good luck.

[Highbanked Hauler]

Is the broken stud flush or below the surface of the head?  There's a few ways that can work w/ planning and patience.  First, center punch the center of the broken stud.  This can be tricky to do.  You can buy left hand drill bits online, Eastwood, maybe Harbor Freight has them.  A reversing drill is necessary to use them.  Start with 3/16" and work your way up to 9/32"  Then you can attempt an Easy-Out or other bolt extractor.  Warming with a propane or MAPP gas torch can help a lot.  Use a small wrench for the easy out and know your own strength - stop before you twist it off.

If the broken stud is above the surface, weld a 3/8" nut to the end.  You'll need good penetration, correct wire speed, etc.  I've centered 3/8" nuts over flush broken studs and have been lucky enough to get a good weld & they come out.

Good luck.

I am getting set to drop the motor out and I'll get a close look then BUT both studs are broken off below the surface of the head. I have a slow speed 1/2 reversible drill.  Is 9/32 the last size to run a tap through ?

[matrout76]

i've done this too many times...

first, buy some good drill bits.  This is what we use at work for drilling stainless steel and they seem to work the best for things like bolts:   https://www.fastenal.com/products/details/53724?term=black+and+gold+1%2F8%22

Also get some left-handed drill bits that are slightly larger than your pilot drill and smaller than the tap-drill size for the threads.  you can usually find these in sets like this:  http://www.wttool.com/index/page/product/product_id/23322/product_name/RDX+15-Piece+Left+Hand+Jobber+Drill+Set&update_continue_shopping=true

I would center punch the center of the bolt and use a small drill bit to drill a hole all the way thru the bolt, like around 1/8".  measure the depth of the other manifold bolt holes in the block and put a piece of tape around the drill bit so you don't drill too deep.  Drill the hole carefully making sure not to drill into the block.  Once you are all the way thru, spray into the hole with PB Blaster, Kroil, or similar and let it sit.  The area will be warm and help the penetrating oil seep into the crevices.  

Next, take the left hand bit and start drilling out the small thru hole.  Usually, when i'm about 1/2 way thru the bolt, it will stick to the drill bit and back right out.

If that doesn't work, go up one size of left hand drill and repeat

If that doesn't work, try an easy-out

If the easy out breaks    then get a small fender washer with a hole that is smaller than the threads and put it over the broken bolt.  with a mig-welder, shoot the wire down the drilled hole and weld the washer to what is left of the broken bolt.  then, weld a nut to the top of the washer and try to back it out.  If the nut or washer break off, re-weld it.  The heat from welding will help break it loose.

Usually, manifold bolts come out fairly easily since they are no longer under stress.

Good luck!

[Highbanked Hauler]

 Thanks, I'll get the motor out this week and get a look at it. One might possibly stripped threads as the bolt won't tighten, the other is broken about  1/4 in. in the hole.