shearing strength of head bolts

[Nathan Mayo]

I have need to remove the upper head on one of my 717's in my Speedster.
Sprayed all the bolts down with PB and waited several hours, but they aren't just jumping off and I am deathly afraid of twisting too hard. Am reluctant to fire up a torch in the engine compartment to heat up the heads, and I don't want to burn the pretty paint either. We all know that feeling that goes through your guts when you shear off a bolt head and what that leads to. I was thinking that if someone knows the shear torque in inch pounds of a 7 mm stainless headbolt, then I could get a torque wrench and beat'em to my hearts content without fear of snapping, as long as I don't exceed the magic number.
All I have been able to find on the WEB are numbers of how tight to set them in the first place. I need to know the breaking torque number.

Thanks !...........nm

 

[timmyboy76]

you can put some torque on it (loosening) and then smap the wrench/whatever, to shock the bolt. Or try tightening it, then losening.

 

[scooper77515]

Also, try the 50/50 acetone and ATF fluid (auto trans fluid) mix as a release agent. Never tried it myself but hear it is much better than anything marketed.

Do a search, there is an entire thread about the mixture.

I have snapped those bolts a couple times. It doesn't take too much, especially once they have "welded" themselves to the heads.

 

[Chief Engineer]

If you can run the engine and get it hot, hit the bolts with some PB Blaster and let em soak overnight. Put a box end wrench on the bolt and tap on the head with a ball peen hammer while torquing on the wrench. If that doesn't work, get some bee's wax and try that on the bolts. You need some heat for the wax to wick down into the threads, but it works. I've used it on fittings onboard ships I work on when even heating it to cherry red alone wouldn't do the trick. Another option is shocking the bolt with some freon (deminimus release of course). Just make sure you don't have a tree hugger watching you. Just a few suggestions that may work for you.