Out of interest - anyone snapped a headbolt before?

[Robin]

Every time i tighten up head bolts on my own engines (don't care when i do it at work as its not my engine) i shit myself as i worry they may snap, has anyone done up headbolts to the correct torque value and have it snap?

[PeteG40]

no - i shit myself too tho.. hate that creak they make

[Robin]

yeah its the creaking that scares me especially when you have the final angle torque still to do!

[Yoof]

I'll do them, I'm not bothered if they break or not 

[djtez]

mines creaked liked crazy after the 1st 90 degree angle

but i thought after skimming the head so therefore head being ever so slightly smaller and using standard bolts they wouldn't go in as much

i only manage one 90 turn and a 45 angle...

[Fred]

Part of the tightness is quite often the fact that not many People run a Threading tap in the bolt holes on the block to clean then out.
Plus of course you know doubt have used new head bolts but then being as your obviously skilled and fettle Bently`s you will have done all this Robin.

Fred.

[breadman]

Even more important is to clean the bolt holes out thoroughly, regardless of whether they get tapped out or not.
I made this mistake before. I ran a tap down all the head bolt holes and gave them all a quick clean out with a twisted rag. Job done I thought. When I put the head on, a few of the bolts wouldn't go in far enough to quite touch the head - even when "nipped up" with a ratchet. This was due to the dirt from the threads building up at the bottom of the holes, effectively reducing the amount of thread depth for the bolts.
Now I always thoroughly clean the holes out, scraping the bottom of the holes out with a small sharp screwdriver and some WD40. It is surprising just how much crap will be down there.
Now after cleaning the holes out and before I fit the head, I screw all the bolts in to the block as far as I can by hand. Then I put a straight edge across the top of the bolts to see if any are standing proud. Obviously any that stick out are the ones that need further cleaning.
Hope this helps.     

[djtez]

i used brake and clutch seat and soaked inside it then blasted excess out with an air hose, then cleaned over with cotton ear buds..

the wholes were deffinetly clean afterwards

[Fred]

Yeah i should have said that too Breadman as i blasted them with carb cleaner then used the airline to further blow out the crap.

[Yoof]

A toot of oil stops the creaking 

Fred- Robin only makes the tea at Bentley (I add the milk), we're booked in for the sugar addition course next week 

[Fred]

You work there too then Yoof. that`ll explain a bit. But given your Knowledge i doubt that very much. lol.

[breadman]

In my experience, blowing the holes out with an airline doesn't shift the hard scaley shit at the bottom. It really needs scraping loose first with a sharp tool.
Unless the block is totally bare, using an airline down a blind hole is gonna make any dirt fly back out and possibly into oilways or coolant passages, down bores etc etc. Watch your eyes too! Not recommended on a built up short engine.

[Fred]

I have those those rubber boot things that painters put on threads and stuff so they don`t paint them wich i stuff in the other holes + i do my best to blank off the bores. and what have yer. Know what you mean fella with how stubborn the cack in the bottom of the stud holes can be. Back when i ran me mk2 i had the head gasket go and a few of the stud holes were clogged with carbon and as i were going through the manual i saw the Tap bit cleaning out the holes but because my job was a welder fabricator/sheet metal worker i knew only too well of all the swarf and rocol cutting compound falling to the bottom of the tapped holes. And if this was a blind hole as the stud holes are then yes, you would end up compressing the cack in the bottom. As i remember it, i did use something to scrape the bottom of the holes out.
Good job Really that all who answer come up with various bits to do as we don`t always think of everything when we reply too post`s.
But then thats what makes the internet and PoloG40 great.
+ i have a Laugh every time i come on here at some post`s wich of course are intended to be funny.
Together we make a Team and thats what its all about.
All the best for 2009 everybody. Think we`re gonna need it as well with the way things are at the mo.
Regards, Fred.

[Dan]

I would avoid running a tap down head bolt threads ! it could undercut the already good thread that was put in by much more precise engineers than someone in a  garage with a tap and die set !

Fair enough if you only have the thread chasing type that don't actually cut the threads just clean them, but you can just run a clean head bolt in and out as easy to check it's clear.

Clean the holes out with a nylon engine gallery cleaning brush and plenty of degreaser etc. once it's dry, maybe a little light oil run down with a clean head bolt.

[Fred]

I have thread cutters and chasers but i still run a tap down the threads mainly coz i know what i`m doing.
Never cut more metal out meself but then the carbon build up is softer than the cast iron.
I`ve seen the tapping of a new block and they use spiral machine taps that eject swarf as they cut but of course being cast iron wich cuts making fine chip dusty swarf they still drive the tap in and out several times to help clear the new cut thread.
also they use a tapping head that automatically reverses if it jams.
if your carefull and don`t go at it ham fisted then it does the job fine.

Fred.