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broken cylinder head stud
#1
Hi all

putting the engine back together and whilst putting new cylinder head studs in.....one stud snapped flush with the block (stud between no 2 and 3 cylinder). I was trying to put car back together for Cotswold trial. Would it be a wise move to run the car minus one stud. Or is this considered to risky? 

thanks for nay help 

ollie cox
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#2
Will be more or less end of head gasket, and some risk of  internal water leak, perhaps even hydraulic lock. The uneven pressures stress the block and, as with excessive tension, tend to promote cracks. It is largely to avoid this rather than permanent distortion that heads are tightened progressively.
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#3
(11-11-2017, 12:47 AM)ollie cox Wrote: Hi all

putting the engine back together and whilst putting new cylinder head studs in.....one stud snapped flush with the block (stud between no 2 and 3 cylinder). I was trying to put car back together for Cotswold trial. Would it be a wise move to run the car minus one stud. Or is this considered to risky? 

thanks for nay help 

ollie cox

Too risky. You'll blow the gasket and have a wasted day!

You really need to get the stud out and replace it. If the engine is in the car it's awkward but doable with careful drilling the centre of the stud  and progressively using bigger drills (new, good quality drill bits). When it's almost to the root diameter of the thread I then fold the stud in using a small, sharp centre punch.



Charles
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#4
Ollie,
I'm with Charles on this one, you don't really have an option.
J
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#5
(11-11-2017, 09:03 AM)Charles P Wrote:
(11-11-2017, 12:47 AM)ollie cox Wrote: Hi all

putting the engine back together and whilst putting new cylinder head studs in.....one stud snapped flush with the block (stud between no 2 and 3 cylinder). I was trying to put car back together for Cotswold trial. Would it be a wise move to run the car minus one stud. Or is this considered to risky? 

thanks for nay help 

ollie cox

Too risky. You'll blow the gasket and have a wasted day!

You really need to get the stud out and replace it. If the engine is in the car it's awkward but doable with careful drilling the centre of the stud  and progressively using bigger drills (new, good quality drill bits). When it's almost to the root diameter of the thread I then fold the stud in using a small, sharp centre punch.



Charles
To start with a good centre for drilling put the head in place on the studs and choose a drill which is the best fit in the hole of the broken stud, then start drilling into the broken stud just a very little. Take the head off and you will have a good centre in the broken stud from which to start the proper drilling out. You may prefer to put the head back after checking that the start is central, because the head can provide a useful indication that you are keeping the drill vertical.
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#6
Hi Ollie,

If it was my only way to get home I'd run it, not if I had a choice. Especially not with any kind of alloy head as you are asking for it to warp.

It troubles me a little that you managed to shear a new stud putting it into the block... I normally just nip them up. They ought to be comfortably able to cope with 20lbft. Was it perhaps a bit too much enthusiasm?

Chris
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#7
I guess the old one snapped taking it out.
Jim
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#8
Hard luck and frustrating dilemma but no brainer with an Alloy head. On a slightly tangential tack what are regarded as 'good quality drill bits' ? I don't seem to have had any lasting that long but that's possibly due to my lack of skill.
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#9
For cutting into hard metals, I've always found cobalt drill bits to be the best.

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#10
Photo 

.pdf   A7 Head Stud Guide.PDF (Size: 155.59 KB / Downloads: 1,777)

Woodrow Manual gives a very useful tool for drilling out broken head studs, pilot hole first then hole for tapping a new thread, the guides help take out the chance of getting it misaligned. Good luck with this!
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