Thread: head bolts - help.

How so, Benji? Can't you get enough torque on them to undo? Does it feel like you're going to pull the thread out of the block?

First up, try a longer breaker bar or get a bigger torque on the 30" bar. Unless someone's used a thread locker on head bolts (and you'll be able to check by the residue on the inner bolts), the TTY bolts remaining have been overdone big time.

Good luck with the outage!

Pete

I normally I try a few things on bolts that have seized, mechanical shock and heat cycles normally do it. An air ratchet does a good job of applying lots of little shocks and if big enough will either come or snap the bolt. Getting heat into a head bolt might be a bigger challenge. My mechanic tells me he can burn the head of a bolt with the oxy and not damage the material under it.

G`day ,

as long as your using a single hex socket and an impact type is most suitable i`d suggest , then a length of pipe on the breaker bar will undo them , if the threads pull , helicoils will solve .

If you`re not happy doing that , you can if you have good bits , drill the heads off and then unscrew by hand the leftover shaft , i`ve found .

Use the bolts removed as a guide for diameter .

I had a similar problem. Blknight came to the rescue with a decent length breaker bar and 6pt impact socket ... he then whispered some inaudible incantation and the bolt slowly emerged....

I'd be extremely cautious about putting an oxy torch anywhere near an aluminium head! I'd use slugburner's suggestion of using an air rachet to shock the TTY bolt and break any crystalline deposits using a low torque setting (around 40 ft lbs max) so as not to snap the bolt.

Aluminium has a coefficient of linear expansion about 1.5 times that of steel. Heating the head is going to cause it to expand faster than the bolt. While the bolt hole may expand, the head will also expand upwards faster than the bolt will lengthen. So the bolt is going to be 'stretched' and its clamping force increased..

Thanks heaps guys, much appreciated.

Some idgit has lock tighted them - that seems to be the prolem.

By shocking them we've managed to get all of them out of the left bank bar 1; it seems to be that the bolts are a poor interface 5/8, and we've rounded two of them so far.

Might leave it for tommorow and go and get a 6 sided 5/8.

The breaker bar and 6 pt socket worked on all but one of my head bolts on my V8. I ended up grinding the head off the bolt with a mini die grinder and lots of patience. Took me hours to do, but as soon as the head was off, the bolt shaft undid easily with my fingers.

if you havent removed the bolts in the reverse of the magic number you my find that the head hass "tilted" and is putting extra pressure on the remaining bolts.

Try winding in the bolts again, tightening them up (in sequence as best you can) then undoing the outer bolts 1/4 a turn.

when removing head bolts (or pattern/sequence tighten bolts) I generally remove them with the reverse procedure to tightening them.

before you go leaning on the long bar make sure you have the best fitting socket you have fitted to the head of the bolt, this may mean using an imperial on a metric and vice versa depending on the quality of your sockets and any damage on the bolts.

a 5/8 or 16mm 6-sided shallow impact socket should do it. I've also seen advice to hold a brass drift on the bolt head and give it a sharp whack with an "engineer's" hammer to shock the threads vertically.

FWIW:Be careful about the order of removal!! Start from the outside and work inwards to remove. Don't be tempted to forgo the correct order because you don't know what stresses are on the head as regards further warping..

Good luck tomorrow!