Thread: Terrified about breaking a head bolt - can anyone ease my anxiety?

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Induction heating of bolt.
I want one.
Regards PhilipA

Just undo them, Ive never broken a head bolt . Just restored a 1949 Dodge side valve which has been sitting rusted up and seized for the last 30 years , The bottom of the head bolts on these are open to the water jacket. Reused the same headbolts too.

get into it, if it breaks it needed replacing anyway.

I have had the head off my 1695cc a couple of times in the last 35 years with out a problem . Not sure it had been on the first time I did it The motor is 70 years old now & still the original head studs .

Originally Posted by jedwards

I plan to remove the head from my 2litre petrol this weekend, and am desperately fearful of breaking one (or move) of the bolts off and it costing me a fortune to pay to get that remedied.

I have no idea when they were last off, but certainly not in my 3 years of ownership. Are there any tricks or pre-treatments that could reduce the chances of breakage?

The manual says that they should have been torqued to 50lb/ft for the 7/16" bolts and 30lb/ft for the 3/8" bolts. I have previous read that I should tighten them down a fraction to break any corrosive welding, and then undo them from there. I tried this up at 60lb/ft torque but felt no movement at all.

Is there a technique, using the tongue wrench, that would let me work away at them, without the fear of snapping something off?

Can anyone tell me what the braking stains of old head bolts is likely to be?

Many thanks

Jeff
in Perth, WA

Jeff, use a 1/2" impact rattle gun. I find that the vibration seems to loosen tight bolt better than continuous torque and is less likely to snap off stuck threads. THey also work well on rusty exhaust manfold fastners. Don't panic if the head comes off one of the head blts, one of them is a stud with a nut!


































Dont worry yourself about it unless it has been submerged in salt water for a while. They are tough good quality steel. I always use a 1/2" drive impact rattle gun. I find that the vibration shakes them loose. I also find it good for rusty exhaust manifold studs and bolts as well. One of the head bolts is a stud with a nut, so don't panic if the head comes off! Make sure you set it on loosen - not tighten. Have fun! PS : Get yourself some good quality disposable nitrile mechanics gloves, old Land Rovers are usually very grubby and hard on your skin. Boston degreaser from Bunnings is cheap and effective, but hard on skin. 5380

Tightening prior to undoing is no biggy.

Have done it all my working life.

You may not visually notice any movement but there would have been some & it just breaks the seal, especially if you have applied WD40 or similar, well beforehand. This method worked extremely well before stuff like WD40 etc was on the market so go for it, but don't be too heavy handed. I mainly used a Ring Spanner as not sure you will get the same movement with an open ender.

The important thing when replacing them is to make sure your threads are clean to the bottom of the thread on both the holes & the bolts. A drop or two of engine oil before inserting the bolts could be good insurance for the "next time".

My neighbour spends a disproportionate amount of his time removing broken head bolts (oddly enough he does quite a bit of work for LR with Td5 blocks). The general advice is if you break one, don't attempt to remediate it yourself but get professional help first.

It's a lot easier to remove the remains of a bolt than it is to remove the bolt which has been drilled off center and the hole is now filled with a snapped EZ-out, complete with thread damage to the bore where the drill bit that made said hole slipped and ate into the thread. I've seen much worse, and they are usually the subject of the "friday arvo beer and head shaking sessions".

To add to other good advice given up-thread, a couple of good belts with a heavy hammer on the bolt head has also been known to loosen stubborn threads. The vertical movement can sometimes help in breaking loose a corroded thread.

Originally Posted by jedwards

I plan to remove the head from my 2litre petrol this weekend, and am desperately fearful of breaking one (or move) of the bolts off and it costing me a fortune to pay to get that remedied.

I have no idea when they were last off, but certainly not in my 3 years of ownership. Are there any tricks or pre-treatments that could reduce the chances of breakage?

The manual says that they should have been torqued to 50lb/ft for the 7/16" bolts and 30lb/ft for the 3/8" bolts. I have previous read that I should tighten them down a fraction to break any corrosive welding, and then undo them from there. I tried this up at 60lb/ft torque but felt no movement at all.

Is there a technique, using the tongue wrench, that would let me work away at them, without the fear of snapping something off?

Can anyone tell me what the braking stains of old head bolts is likely to be?

Many thanks

Jeff
in Perth, WA

In a similar way to the rattle gun idea, I always hit the head of a bolt with a hammer, spray with crc, leave it for a day, repeat until I'm willing to give it a go. I had to do this daily for two weeks once to remove a bolt, but it worked.

Cheers,
John