Headbolts!!!!!

mrbump · Post by **mrbump** » 22 Sep 2003, 01:22

hi,
I am having a huge problem removing the headbolts form my zx volcane td. The last owner has made a bad job of a headgasket change - exhaust and inlet manifolds were both leaking at the gaskets, but the worst is the sheer force that holds these headbolts in!!!
I have so far snapped 3 torq bits, one ratchet and one chrome vanadium extension peice.[:(!] I have tried taking the bolts out using a master bar, long ratchet and finally a torque wrench set at max 250 lb/ft with a 4ft steel tube on the end for leverage - the torque wrench was clicking away long before anything budged!!![:0]
I am taking out the bolts in the correct order, and using the correct torq bit. The first two (flywheel end) came out ok, but the third (front of head at timing belt end) is the one that is really stuck. I have tried the other bolts as well (not in the correct sequence) but they are the same way and won't move.
All I can think of doing now is to weld on big 17 or 19mm nuts to the top of the bolts and hope that the heat and the extra leverage of the big nuts can shift them.
But I cant help thinking that there must be an easier way? Is there?
Also, will the over torqued bolts have caused damage to the head or even the block?
TIA
[:)]

tomsheppard · Post by **tomsheppard** » 22 Sep 2003, 01:38

this is usually likely to mean that the bolt is corroded in but you have only recently had them fitted. If they are not new bolts, (And that is not a reccommendation, that's a necessity) then the job has been bodged. The bolts are designed to stretch when correctly torqued down. I won't speculate on damage, but there ought to be washers under the bolts, and if they are not there, then the bolts may have grounded in their holes. If there are washers present soak your tight bolts in DERV for a day or two and try again. If that fails, then consider this: The head was fitted recently, right? If so then the bolts are at least free in the head.
Drill the tops off them, lift the head off and then weld nuts onto the remaining studs. It will take time and considerable aggravation, I'm afraid but it is the most likely way to remove the head

mrbump · Post by **mrbump** » 22 Sep 2003, 01:55

tom,
Just keep me right here - So, there isnt actually any threading inside the head casting, i mean its not held to the headbolt by a threading inside the aluminuim of the head? So the only threading is inside the block?
I didnt think of doing it that way round! Taking the tops off the bolts and removing the head will give me alot more room to mess about with the bolts when they are still stuck in the block. Thanks for that.
Yes, the head was changed in 2001 so nearly 3 years ago. Some of the headbots were a little 'chewed' when I looked at them, so I suspect that this is damage caused when removing them the first time, rather than damage when they were put in (as the chewing is on the side that would be used when loosening), so this makes me think that they have never been changed.
There are no washers under the bolts, you dont mean the inch long spacers do you?
I have the bolts soaking in wd40 for now and I will put deisel on tommorrow.
Thanks[:)]

andycarter · Post by **andycarter** » 22 Sep 2003, 02:19

The cylinder head bolts pass through plain holes drilled in the head, there is no thread in the head otherwise the bolts would not compress the gasket.
Be carefull when drilling that you catch all the debris.
I would expect that the bolts will have stretched in the reduced diameter shank, this behaviour is by design to ensure that the amount of preload in the bolts when tightened is sufficient to prevent fatigue failure of the bolts.
It is unlikely that the block is damaged unless:
1. The thread was mangled or dirty and the bolts refitted.
2. The wrong type of bolt was fitted with the wrong thread form.
3. A bolt which has stretched in the threaded area would tend to strip the thread (in an alloy block) before reaching full torque because of the differing thread pitch between the two parts.
Andy

AndersDK · Post by **AndersDK** » 22 Sep 2003, 02:23

Washers under bolts are approx 2-3mm thick.
With head off - soak the stud threads with DERV - let it work overnight - then vibrate on the studs with an airdriven hammer.
DaveBurns advised me to do so on a single headbolt snapped on a BX 19 diesel.
It was amazing - almost a miracle - to watch the rustgunk moving out from the threads - while i vibrated/hammered on the stud.
The stud could be removed by hand afterwards - the most amazing experience I've had for y's [^][:p]

tomsheppard · Post by **tomsheppard** » 23 Sep 2003, 00:52

ANd when you come to reassemble the whole plut, Cut two slots down the thread of the best of your old bolts and run it backwards and forwards in each thread , cleaning it with a rag and a squirt of WD or similar each time it comes out. This will take you an hour, 'cos the threads all have to feel the same, that is clean and smooth, fully down and fully up. This will help you to achieve a constant pressure across the head as you torque it down. I am surprised how many experienced mechanics just bang a new set in, ignoring the friction that the rust and gunge in some threads must contribute to the torque needed to turn the bolt!Good luck with the job, I had a lot of help on this one round about February on a BX19 tgd and there are quite a few posts on here concerning that job that might be useful to you.