Manifold stud sheared

[jamesheath]

Hi all,

Looking for advice on my next challenge!
One manifold stud had a poor thread, so we removed it (it came out pretty easily using a stud extractor).
One other has been replaced in the past with a stainless one.
So it seemed sensible to replace the others.
Mistake.
The next one I tried sheared off. Drat. That was a mistake.
I now have to extract the remains:   pic of remains

The approaches would appear to be:

1. extract the remains and use a bottoming tap to restore the thread at 1/4 BSF
   
2. drill out larger and use a helicoil
   
3. drill out larger and use a stepped stud
   

I've used approach 1 successfully with the lower water branch studs, so this would be my ideal approach.
I wondered what methods & success people have had with this - I realise that ideally we'd have a jig, or use the manifold and a turned insert.
Unfortunately I don't have a lathe.

I managed the water branch with a drill bit in a drill press and no guide, but it did not go perfectly centrally, and it was a bit heart in mouth. It also helped that there was a hole right the way through.

Thanks!

James

[bob46320]

First off, try number 1 - If it doesn't clean up, I prefer the helicoils. Stepped studs are OK, but they are a bugger if they start to unscrew from the block when you are only trying to remove the nut and leave the stud in place.

[dickie65]

I have never had any success with any of the stud extractors that you insert into a drilled hole in the stud. They either snap or expand the stud you are trying to extract and jam it tighter in.
I have had success drilling out studs then using a Rats Tail file to open the hole out until the old stud is down to the thread in the parent metal then either picked out the twists of stud or used a tap to remove the last bits.
Its a good exercise in drilling accuracy and hand filing as well as patience.
I have used a decent cordless drill as they are soft start and easier to control than a mains powered drill.

[Stuart Giles]

Try to drill out the busted stud and re-tap @ 1/4" BSF first, if that doesn't work then a Helicoil would be my next choice.

If you have a cordless drill which has reverse, using a left handed drill bit in it will usually spin out the remains of the thread before the drill has gone full depth. Left hand drill bits are available on that well known auction site: https://www.ebay.co.uk/itm/NEW-Dormer-HS...SwVjVeqs-p

[Chris KC]

I think you have the right idea James. 1 is the way I'd go and 2 / 3 are satisfactory repairs if it goes bad.

The knack is to get the drill square and centred, if you succeed there you'll be fine - don't just eyeball it, utilise any means at your disposal to get it right.

Like Dickie I have no positive experience with extractors - not for a stud broken below the surface anyway. Though this is greatly to your advantage as you can use the mouth of the hole to assist centreing. You don't need a lathe to make a drilling guide - just three holes in a scrap of steel plate which you can locate on a couple of adjacent studs and through which you can make a pilot hole.

Never tried one myself but I've heard of people using self-centreing bits these in circs like yours (- they are designed for drilling holes through door hinges). This is just an example:

https://www.leevalley.com/en-gb/shop/too...drill-bits

[jamesheath]

The stud remnant is out, and I'm pretty sure the thread is still perfect!
for future searchers I thought I'd write out what happened.... as I was very scared by this process, but needn't have been I think.
This was the stud remnant we were working on - quite lucky in some ways, as it's neatly sheared off flat, and is slightly recessed in the block:
   

Following a neat suggestion for head studs from another post, we bolted the manifold on to use as a guide. We then checked the alignment with a boroscope (very useful thing, and very cheap on ebay). 
   

this showed us that the natural alignment was way off. We tweaked it and got it pretty good:

  2nd boro.png (Size: 401.8 KB / Downloads: 388)

As suggested in the other post, we then drilled with a bit that was a snug fit in the manifold hole. The result was an impression in the centre of the stud remnant - good. however, that impression has a flat in the middle of the hole, as my drill bit creates a small flat area (all of my HSS bits seem to have this):  this meant that after all that, I still had to eye it up & centre punch it. 
   

The next step was to try and drill straight down the stud. We went to great lengths to arrange the block on the dillar drill, but TBH we weren't sure we were truly lined up and the depth of drilling isn't that much, so I'm not sure I'd bother next time:
   

On the advice of another friend I then proceeded to drill out with successively larger reverse threaded drill bits, in a hand drill on reverse.
(The idea being that they might whisk out the remains of the stud). I'm not convinced that they really did this, though if I'd progressed to a big enough bit they may have. instead, we stopped having just nudged the biggest bit I dared to use in to the opening. This then exposed enough thread for a bottoming tap to grip, and we then very gently cut the rest of the stud out working the tap back & forward, leaving a lovely clean thread.

On to the next challenge!

[Colin Morgan]

Glad you have managed this successfully.  Just to say, my car has been running for a couple of decades with the manifold held on with 6 out of the 7 studs in place - it is the end LH one that is missing.  The manifold is very rigid, so seem to have got away with it - no leaks.  Had the manifold off a couple of times and used a good copper-type gasket when refitting.  Intend fixing it properly when the engine finally has to come out - which, being a three-bearing engine, could be anytime?

[Steve Parkin]

My 1932 RN also has one stud broken off (front exhaust). The manifold is also secure and doesn't leak so it's not really noticeable. My view is also to sort it out when the engine has to come out.

[Jamie]

I know that this is an older thread, but I had to drill out a snap stud as well recently, this in the crankcase. As it was too large to fit into my bench drill, I used the bench drill to put a hole in a thick steel plate. I then aligned this carefully over the broken stud and clamped it firmly with a sash cramp. This enabled me to drill the stud out accurately. The thread was manngled, so needed to be Helicoiled.

Regards,

Jamie.

[John Mason]

I see in one of the photos that James is using flat washers between nut and manifold. I was told in the past they are not necessary. Does anyone else use the washers and is that the correct way of fitting the manifold.

John Mason.