I started taking apart the cylinder head for a head gasket change and I noticed my hex bolt won't break free. Any tips? I've tried using a hammer + breaker bar and that didn't do anything. The previous owner had the headgasket repaired at a shop.

 

That bolt should only be torqued to 36lbft so shouldn't be that hard to remove, sounds like it's been over torqued now though.
I would try using an impact wrench instead, less risk to snap something.

 

Another trick that I like to use on really tight critical fasteners is to use heat gun and freezing spray.
Apply the heat to the "nut" area as isolated as possible, then use the freezing spray on the bolt and after that be quick to try and unscrew it.
More temp difference equals less torque to break it free.

 

Don't use that socket on there, as the chance of stripping the bolt is high. Instead, clean the bolt head really well, dry it, and use a good quality Allen key with a cheater pipe. Apply sudden torque in a single motion to break it loose.

 

Fatjoe, why do you suggest not to use that socket? Just asking as that's what I would probably use and maybe I'm missing something. Also how do you think the allen key is different when the socket and allen key (essentially) use the same head?

 

I think he just means don't use the long handle as a way to generate lots of torque on the bolt. Instead whack it all at once with a heavy rubber mallet, or one of those orange shot peen hammers.

You can do that with either allen socket or allen key.

 

 

I admit I lack the vocabulary to explain this, but I will try. With this setup, there is a chance the socket will twist off as you apply force to it, stripping the bolt. use either a stubby socket or the allen key. You want to keep the torque source as close to the bolt head as possible to insure good torque transfer. Use a quick snapping force on the bar.

 

So the issue seems to be the adapter for the 1/2" drive breaker bar to 3/8" allen socket. That and the length of the allen part of the socket. There is no socket extension being used in the photo.

We've all been there trying to loosen w stubborn faster when an extension is needed for clearance. The torque just wants to fold the socket over, instead of rotating out the fastener.

That doesn't seem to be much of an issue here though.

 

I'm not sure I follow the logic, but I am only a 'weekend' mechanic. I do see a distinction between the torque of a breaker bar and an impacting force. In which case would a suitably sized impact do a better job than hand tools? I'm always a little hesitant to use impacts on alloy components though.

Concerning the head of the tool though I thought an allen-key socket would have more tensile strength than a traditional allen-key. I'm interested in this as things like the prop shaft allen key bolts are notoriously difficult on AP1's (though I've never tackled them) and if there is a best practice to follow I'm keen to hear it.