I briefly bored people about this before on my (now lost!) KR head swap head, but I'm still worrying like a baby over it. Basically, one of the head bolts on the 16V head I just fitted was overtightened by up to quarter of a turn, and I'm wondering if I should just forget about it, or should I think about refitting a new set of bolts / gasket. The new head is a very nice polished, ported and skimmed one and I'd be gutted to have done any damage to it. Any thoughts? Could the uneven torque cause the head to warp slightly or am I being completely daft? Edited by: Trev16v
The car has been run for just a few hours since doing the swap. It had a brand new gasket, of course. It would make things far easier (obviously) if I could just put a new set of bolts in without having to take the head off again and put in yet another new gasket, but I suppose that would be a bad thing to do.
have you done a compression test since? maybe if that shows that the compression is diferent for the cylinder where that bolt is you should worry, but if they're all the same, then don't worry. (i'm no expect - just an idea)
That's a thought. But even if such a test gave positive results, I'd still worry about the bolt being left like that having possible long term damage on the head.
as its been run you cant change just one. in an ideal world you would replace the whole set again.but we all know how much of a pain in the ar5e this is. is only quarter a turn? i would be tempted to do them again [:^(] Edited by: alex9107
no point yourd have to start again as there done in stages and order to pull the head down flat if one has been overtighened then lossebed or replaced the head gasket will be crushed and could fail. quarter of turn can be quite a lot more torque than you think. [:^(] Edited by: alex9107
Replacing a set of head bolts to me doesn't seem like that much hassle. I would not mind doing that. What I'm wondering though is if I could get away with not lifting the head and replacing the gasket. But I guess the answer to that is no, that would not be sensible.
I've overtightened one in the past, and it sheared clean in half under the stress. Luckily this happened when I actually overtightening it!! I had to take the whole lot off again, but fourtunalty the snapped piece just un-screwed. If you want piece of mind, take it out and change it. It maybe ok to re-use but for 2 it isn't worth the risk.
It should be fine - the VW bolts are stretch bolts and stretch top apply the correct torque. I would just leave it and it'll be fine. Why bother changing the bolts and gasket now, when it may be fine, wait and see if a problem develops, if it does then its the same amount of work, If it doesnt then you're saving yourself a job.
Let's be honest, if it's been run for a few days like it, it will be ok, but if you're worried about it you best start again, you won't be happy until you know it's been done properly... don't just replace the bolts though, head has to come off again Just think Trev - At least you'll be more confident this time. But - Will the head be straight now?....
Indeed I did wonder if the bolts (Victor Reinz) are engineered to stretch to compensate if too much torque is applied. And Andy you're totally right - I could just use the car and see how it goes. What concerns me though is if it's actually possible to warp the head by having an un-even torque on the headbolts. The head has just been skimmed (as well as other work done) and I don't want to chance damaging it.
Just out of interest, which bolt was it in this order?? cambelt on the left side 1,6 1 2 3 4 5 6 7 8 9 10
I am 95% sure number 4. I will look at the photographs and check this (it's obvious, since that bolt head also happened to get rounded accidentally... oh god, this sounds really bad doesn't it).
if they are stretch bolts, this basically means that a portion of the bolt yeilds to a plastic state (as opposed to elastic) as you apply a stress. now as you tighten this further, the portion that it plastic, gets longer and longer as more of the elastic metal gets transformed to plastic metal. you can notice this yeild point when it happens, because the torque required to cause the plastic deformation is constant - so the bolt will not feel like its tightening up any more. now if you keep tightening and tightening - eventually most of the shank will be plastic, it will reach its yeild point, and then snap - hey presto - the reason why not to re-use streth bolts. So to sum up, you should be OK with an extra 1/4 of a turn - because the portion that has become plastic from this extra strain is prob not significant, compared to the total length of the bolt. Jules
of a turn is nothing to worry about, as long as you did everything else ok you wont have a problem. Forget about it.
Okay, understood, and thanks again for your kind advice because I'm getting all stressy over this at the moment. I think it could have been significantly less than 1/4 of a turn. He said '30 degrees' to me. I'll ask him again if he's sure that's about all it was, but I'm taking 1/4 as a worse case. Unfortunately I was not there to see at the time (was busy polishing the inlet manifold nearby!). jcorallo, what you've said is very interesting and I do hope that the extra torque has been absorbed in the bolt. But if gasket problems develop later on then it isn't a great deal to redo the entire lot. It's the thought of having possibly warped the head that bothers me!
