Head bolts

J

justthisguyhere

Member
Hello I have broken a head bolt well putting the cylinder heads back on after a gasket change...thankfully got the broken bolt out without issue...my question is what bolts I use to replace this? It's a 14 bolt metal gasket v8 from a rover p6b...so i beleave these to just be grade 8 high tensile bolts and not stretch bolts? (I read that somewhere on this site thankyou to who posted that) so does that mean I can just order any grade 8 high tensile bolt with the same mesurment? And also if anyone could give me the torque specs for the heads and inlet manifold please as I believe I may have been useing specs for a latter engine
thankyou all in advance for the help
 
They aren't stretch bolts. Personally I'd get a used bolt and use that. You'd be unlucky to have another one snap.
Head torque is 65-70 lb.ft, except for the outer row which can be done to 25lb.ft.
 
harveyp6 said:
They aren't stretch bolts. Personally I'd get a used bolt and use that. You'd be unlucky to have another one snap.
Head torque is 65-70 lb.ft, except for the outer row which can be done to 25lb.ft.
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Thank you for that harvey i would follow your advice but it's been very hard to source any parts in my part of little new Zealand but I found a place that can get me all the bolts at the same grade 8 strength and I am afraid to break another bolt so I thought replacing them all would be for the best (I could try look around some more for a second hand set of bolts as there must be somewhere in NZ that has them) I already have the new bolts ordered and they should get here tomorrow do you think that I should stop the order and look around for a set of second hand bolts? Will it make much difference if I go new or second hand? Thank you for your help
 
The only problem I can think of is that normal bolts won't be waisted, which ISTR the head bolts are.

Which row of bolts had the broken one?
 
harveyp6 said:
The only problem I can think of is that normal bolts won't be waisted, which ISTR the head bolts are.

Which row of bolts had the broken one?
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I took the bolts to a machinery place here and they said they where grade 8 high tensile bolts and they ordered in all difrent 28 bolts (though I need to reuse a bolt from the left side lower row because it had a dipstick mount for it not sure if that's standard or not) I have got a text from the shop not too long ago saying the bolts are in (I haven't paid yet so can still turn it down if you think it's a bad idea)
It was the right side head cylinder, top row furthest bolt on the right
Snapped right at the threads I can't remember the tourqe it was on I think I was on the second round of tightening to tourqe

So should I go get these bolts and put everything back together? Or wait and look for a second hand bolts?

Thanks again for all your help and knowledge
 
harveyp6 said:
The only problem I can think of is that normal bolts won't be waisted, which ISTR the head bolts are.

Which row of bolts had the broken one?
Click to expand...
I don't have a bolt on me to check but i think they did have a flaring at the top so if these new ones don't have that it's a no go?
Thanks
 
I'm not sure how to add this photo to my last message so I'll put it here I'm probably makeing this thread all messy sorry but yea here is the bolt that little flair at the top is what your talking about? That's "waisted"? (I don't really know much about bolts) thank you for the information
IMG_20200924_111442.jpg
 
This is one of the bolts they are high tensile 9 instead of 8 and the size of the "waist" goes right the way down to the threads will this cause issues? The threads and lengths are the same just a bad angle
IMG_20200924_120532.jpg
 
They may be waisted to stop them getting seized to the head due to corrosion. You could put copperslip on the unthreaded part. If you put any sort of lubricant on the threads you will need to re check the torque values.
 
cobraboy said:
They may be waisted to stop them getting seized to the head due to corrosion. You could put copperslip on the unthreaded part. If you put any sort of lubricant on the threads you will need to re check the torque values.
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I do have some copper anti seize grease I can use i thought it was to be used on everything anyway? I'm rather new to this and would have no idea how to check what to change the tourqe value to...would I be going up or down in tourqe? Any direction you can give me is helpful otherwise I hlmah have found where I can get a set of second hand motor studs though I would probably still use the copper anti seize to be safe

So reading about it sounds like I need to go to a lower tourqe if I use anti seize...maybe the fact I put anti seize on the threads and tourqe to spec was what caused the bolt to break or maybe I was unlucky this is my first time changeing head gaskets so never dealt with this stuff before
 
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You are correct, lube on the threads means a lower torque value. I think it best just to coat the shank and stick with the recommended setting. if you did copperslip the threads and used original settings there is a real possibility that was the cause of your breakage.
There may be a decent clearance between bolt and head, I cannot remember. I do know holes in alloy heads close up dramatically when corrosion sets in. Trying to get Jaguar XK heads off the studs is a real PITA.
 
cobraboy said:
You are correct, lube on the threads means a lower torque value. I think it best just to coat the shank and stick with the recommended setting. if you did copperslip the threads and used original settings there is a real possibility that was the cause of your breakage.
There may be a decent clearance between bolt and head, I cannot remember. I do know holes in alloy heads close up dramatically when corrosion sets in. Trying to get Jaguar XK heads off the studs is a real PITA.
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So do you think getting a set of second hand studs is a better idea than useing these other high tensile 9 bolts with the wider shank? I'll check the clearances with the original bolts Tomorow if there is enough room between bolt and head I might be ok?
Thanks for your advice
 
If I had the bolts and they were not tight in the holes, would I use them ? - yes I would. They are not stretch bolts, and the grade you have is higher than stock.
As stated earlier, the outer row do not need the same value as the others.

Rover may have waisted those bolts for reasons of flex and yield, but tbh as you are using a tin gasket I would not be worried.

Just keep in mind that these blocks are not new, feel your way in stages to the recommended settings using the correct tightening pattern (order) and if something does not feel right ( a bolt going easy ) do not push on until you have checked all is well.
 
cobraboy said:
If I had the bolts and they were not tight in the holes, would I use them ? - yes I would. They are not stretch bolts, and the grade you have is higher than stock.
As stated earlier, the outer row do not need the same value as the others.

Rover may have waisted those bolts for reasons of flex and yield, but tbh as you are using a tin gasket I would not be worried.

Just keep in mind that these blocks are not new, feel your way in stages to the recommended settings using the correct tightening pattern (order) and if something does not feel right ( a bolt going easy ) do not push on until you have checked all is well.
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Thanks for that I'll check the clearance Tomorow and go from there
When you say "a bolt going easy" what exactly does that mean?...just incase I encounter this thanks
 
When torqueing up try to feel how much effort you are putting in to get the wrench to click, if all of a sudden a bolt turns with less effort STOP !

It will mean either the bolt is going to break or the thread is stripping in the block.
 
cobraboy said:
When torqueing up try to feel how much effort you are putting in to get the wrench to click, if all of a sudden a bolt turns with less effort STOP !

It will mean either the bolt is going to break or the thread is stripping in the block.
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Thanks for the info...so I still go up in stages of tourqe till I'm at the specific tourqe required right? Like 3 seperate rounds of bolt tightening? Or do I go to full tourqe specs for each bolt right off the bat since they aren't stretch bolts? Thanks
 
cobraboy said:
When torqueing up try to feel how much effort you are putting in to get the wrench to click, if all of a sudden a bolt turns with less effort STOP !

It will mean either the bolt is going to break or the thread is stripping in the block.
Click to expand...
So the new bolts shank is 10mm all the way down and the head cylinder holes are 11mm do you think that 1mm is enough clearance to not worry about them seizing? Along with the copper anti seize on the shanks
Thanks again!
 
In view of your location and the possibility of dropping onto a used set of OEM bolts slim, I think you should be fine with what you have and using anti seize as a precaution.
 
You mention 'second round of torqueing' - AFAIK this model does not require such a process - the book says tighten gradually in sequence with a finish torque of 65-70lb/ft on bolts 1-10, and 40-45 on bolts 11-14 (AKM3621) - on these last 4 you might go with the 25lb/ft given above. If you have tried to do a tightening involving a torque and then some angle tightening that might explain the breakage. Elsewhere Ron relates that LR now specify to lightly oil the bolt threads, rather than use a special sealer/lubricant. I once had to pull a RR head due to it swallowing a carb needle retaining screw, and a rear bolt snapped off flush with the block as I undid it - the stub unscrewed easily once there was no load on it.
 
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