Removing broken head bolt?

[38racing]

boy, if you turned it out with that short a leverage then it had to be the welding heat that loosened it up. maybe we should touch the arc welder tip to every head bolt before we attempt to remove. Where did he put the ground clamp?

[jdm]

boy, if you turned it out with that short a leverage then it had to be the welding heat that loosened it up. maybe we should touch the arc welder tip to every head bolt before we attempt to remove. Where did he put the ground clamp?

Great idea and great success... however just some thoughts.

If the ground clamp is on the block and using a -ve earth, the current passes through the block across the thread, up the bolt to the electrode. The corrosion may be resistive and will generate a heat spot too. (+ve earths the current flow is the other direction)

The heat may help break the corrosion. If there is to much heat in the thread area, it may further weld it on. (more likely on cast).

Also, becareful if the current is passing though bearings. It can "mark/pit" the bearing surfaces and they will need to be replaced in time.

This is not a critism of what was done, just some shared learnings.

[creia]

"... boy, if you turned it out with that short a leverage..."
The photos are a bit deceiving. The welder indicated to me that he placed an additional tube/pipe (did not say how long) over the short rod he welded to the broken head bolt for additional leverage when turning out the head bolt. (In fact, he stated that the first attempt broke the welded rod off of the head bolt and re had to re-weld it.) I do not know where he placed the ground as I was not there during his procedure. (We dropped it off and came back). In the photos that is my son "re-creating" the procedure for demonstration/educational purposes after we brought the engine back home.
Michael

[bgsengine]

Yup - it works because the heat from welding expands the aluminum *much faster* than the steel bolt (dis-similar metals expand at different rates - that's how a thermostat works) and thus, the bolt becomes looser in the block - as mentioned - it is heavily dependent on where the clamp is grounded to, and also important to make sure there is a good ground - Most likely the ground clamp was grounded to the stub shaft , which was then welded to the bolt head. Clamping to the block, as was mentioned would tend to arc between the bolt and block and weld the bolt to the block even worse. However if the bolt was that clean when it was removed, it sounds like you need to learn a little "zen" - for future reference, it is possible to "feel" whether the bolt threads are moving as opposed to just the head and shank twisting - if you can get the threads just a little loose, apply a good penetrating oil, and then just patience and rock it back and forth - you'll gradually increase the range the threads will turn , an once you have a full turn or two , it becomes easier. It does require developing a feel for it (Become one with the bolt) - but over time an experienced tech can usually avoid breaking bolts (It is why I *NEVER* use air tools when removing bolts until I am sure they are free and will come right out. Nuts, on the other hand, typically are not so much a problem if the bolt comes right out the other side, or has sufficient stud length for vise grips or a double nut after the piece is removed)

[38racing]

I was old to bang the bolts before trying to remove them. Also wondering the engineering reason why bolts are uses rather than studs with nuts. The exposed nuts would provide for using penetrating oil on them. I expect it's because the holding power on bolts is on all the treads equally but using a nut reduces that part to just a few threads and weakest point is still the weakest link. But how about a longer stud and a nut like a threaded rod connector?

[bgsengine]

profit. they used bolts because there were fewer part numbers, fewer parts, thus less expense. Also the studs would tend to stick out and give "catch points" to catch stuff on (clothes, hands, weeds, etc) and get in the way. Manufacturers and engineers have to balance profitability and quality - they'll go as cheap as they can get away with while maintaining some degree of quality.

the bang on the bolt heads trick sometimes worked to break the rust and corrosion loose - when the shank was what was seized - but did not work that often on seized threads. (although hammering the bolt heads after applying a little kroil often helped the penetrating action of the oil. ) Ive had luck also with hammering on the side of the block or head right around the bolt is which adds a little sideways shock in addition to the in-line shock from hammering on the bolt directly...

[RedGoat]

Nice! Who'd a thunk it?