Well... Dad ordered a Helms kit of manuals for his '01 Yukon XL. Over the past year, it's had a slow coolant leak. Last week, he decided to pull the heads to replace the head gaskets. All was well until he got ready to bolt the first head back on. Loaned him my torque wrench, and instructed him NOT to exceed GM's torque rating! Well, apparently, he wasn't familiar with it to know it does NOT yield a LOUD "click" or extreme feel when it "breaks". Long story short, he broke a bolt in the block, at the threads. The threaded part is in the block, about 3" below the deck surface. Tried left-hand drill bits, with no luck. And, bolt extractors aren't long enough to get down in there.


Worse Case Scenario - New/Used 5.3L short block
Better Case Scenario #1 - Drill & re-tap bolt hole
Better Case Scenario #2 - Helicoil insert & shorter bolt


He doesn't want to have to replace the motor. At 160K miles, it's seen it's share of miles, but certainly can go a lot more. I'd prefer the helicoil insert & shorter bolt option, but I don't know the tolerances of the block. There's certainly a great deal of thickness around the hole. Question is, is this the best alternative?

 

it would be hard to do, specially with a hand drill, but if you could center drill the bolt and keep jumping sizes until you get close enough to the threads, you then could use a left handed drill bit to drill out the remainder of the bolt? then just tap the same size hole, basically clean up the threads?

 

I'd do #2 option and forget it. That'd be your best choice and will work great. There should be plenty of threads for good clamping force.

 

Option #2 IMO...I like heli-coils, but never used one on a head bolt, not so sure how I'd feel about using a shorter, heli-coiled torque to yield bolt.

 

Well, I left dad with my two options:

1. Try and center-punch enough to create a good chunk to grip the top part of the broken bolt to HOPEFULLY back it out with the left-hand drill bits I bought.

2. Tap the block from the surface down 3", and use a shorter bolt.


Just got a call from dad saying #1 actually worked! Now, he's sending one head to me to extract a broken manifold bolt from the driver-side head. He tried to remove the manifold, and the holt snapped. He then tried to use an extractor, and the extractor bit snapped! I think he's got the worst luck with this thing.

 

A. A shorter bolt is a no go.
B. Nothing less than a removal would be acceptable to me.
C. The bolt is a case hardened fastener so its tough to work with.

The center part of the bolt will not be as hard and the outer case. Its not much less harder but it is softer than the outer part.

Make a drill guide.
Without seeing the damage..........
As a machinist with access to a lathe I would obtain a new bolt, or better yet a like bolt but shorter and pop it into the lathe and take the steps to drill it hollow. This would be facing off the threaded end, center drilling it, then drilling out all the way through.
The bolt should be long enough to contact the broken bolt but as short as allowed to save the amount of lathe drilling needed.
The hole size should be around 1/3 the size of the bolt.

Then I would run the hollow bolt down to the broken bolt and snug it gently. Then take the same drill used to hollow the bolt out and gently start drilling.
Luck, a quality drill, Tap magic, and patience you will eventually start a hole in the broken bolt. IMPORTANT: Once you get a hole started be sure and pull the drill out every 1/8" inch of depth and blow the chips out of the hole. These harder chips will not run up the flutes and cause the drill to bind and snap and now you have another problem.

Drill it as far as you can. Remove the guide and take a larger drill and open it up some more without getting into the threads. Try a left hand drill again but be careful. Don't chuck the drill bit real tight in the chuck in case there is a problem it will slip instead of snap. It should come right out.

So, take a bolt to machine shop. It should not be to big a charge. Or tell me what it is and I'll make it and send it to you.

 

Interesting insight.... but you must not have read my last post, in it's entirety.

 

I was typing I guess. I hope he got it centered.