1/2" with a long breaker bar/tubing should do it - otherwise go 3/4" drive. Just make sure you're following the correct sequence from the center outward

 

Probably hard to do with the engine on a stand. Would not recommend using an impact gun as head bolts are known to snap in half sometimes.

 

Re: (JoshV70_)

I wish they would break. That way I can pull the head and would not need much effort to remove the remaining bolt.

Seriously? Jack handle on the breaker bar? What is the tightening torque on theses, 80-90? That is a little more than a lug bolt and those are easier to handle.

Many thanks,
Ricky

 

When tightening start at the center and work outwards:
1. tighten to 20Nm (14.75 ft. lbs)
2. Tighten to 60Nm (44.25 ft. lbs)
3. Tighten through an angle of 130 degrees

It wouldn't surprise me if there is thread lock on those particular bolts (that or they've just seized up by being baked in with the over heating?)...but you're actually suppose to lubricate them before installation.
I guess if it were me, I would go with PB Blaster and heat and let it all soak in for awhile before going at it again.

 

Re: (MadeInJapan)

I was able to take one out. Dry as a bone as I suspected. No thread locker, no oil. I managed to split two 1/2" drive 6pt sockets. I have to go get more to finish taking the other 11 out. PB blaster wont do it since they are set in the head and hard to even get a torch in there.

Cheers,
Ricky

PS: Car has never overheated

 

Wow...this is truly amazing. Good luck and please update w/ your progress.

 

Re: (villaconn)

Quote, originally posted by villaconn »

I was able to take one out. Dry as a bone as I suspected. No thread locker, no oil. I managed to split two 1/2" drive 6pt sockets. I have to go get more to finish taking the other 11 out. PB blaster wont do it since they are set in the head and hard to even get a torch in there.

I do know that the re-assembly process, (the final 130 deg. turn), takes the torque over 120 ft lbs. When I did mine, I stupidly used a step down 1/2 to 3/8 drive adapter which had a sheer pin that goes at 120... It's a real adventure when I goes snap!! At first I thought I had snapped the bolt.

To get the head bolts out, it took a snap-on breaker bar and a three foot pipe on the end, plus a lot of muscle!

Going back together, I also chased ALL of my threads with role taps. They will re-form the threads without removing any additional metal.

Good Luck!

 

Re: (villaconn)

Quote, originally posted by villaconn »

I was able to take one out. Dry as a bone as I suspected. No thread locker, no oil. I managed to split two 1/2" drive 6pt sockets.

Been there, done that. It's a bit disconcerting, as one fears ripping out threads.

FWIW, I'll wager the sockets that split were the chromed ones. I've split chromed sockets and fractured 3/8" extensions doing this kind of work.

Fortunately, wearing safety glasses!

Use impact sockets and extensions. They're hardened, but not so much as to split under huge amounts of torque (like chromed sockets will).

 

Re: (RearWheelPaul)

Yes they were chrome. However, not only are impact sockets hardened, they have a thicker wall. I had to machine one down in order for it to fit in the four center access holes which are a smaller diameter than the other 8. Got them all out yesterday. Thanks.

Cheers,
Ricky

 

LOL I split two impact sockets yesterday