Exhaust Blows

[sump]

Hi, 

Has anyone tried to helical or repair a cylinder head exhaust stud with the exhaust connected at all?

The one I'm having trouble with is the right side rear under the alternator so easy to get at, at least.

[maxstu]

Pictures might help. Early or late exhaust? But normally exhaust off to fix.

[sump]

How do you post pics?
 

[Mr Bean]

How do you post pics?

See reminder earlier in general chat but use black square with " i "  in top right of thingy bar when you create post.
As it happens:
Yes I considered that exhaust thing but in the event an engine exchange beat me to it. Every cloud has a silver lining.
 
Things to think about:
This is a bit like neurosurgery in that you could be drilling to within a few mm of the waterway coolant channel. A depth limiting sleeve on drill might be best whatever you do. Cut away images somewhere on forum.
 
As the exhaust is in position you will need to insert helicoil through via the flange – either tapping the flange as well or - as the holes may not be concentric, a generous clearance in the flange. An oversize washer would be needed to span the gap.
 
Care required not letting the drill get dragged into the aluminium head as it breaks through the steel of the exhaust – another depth sleeve maybe.
 
Helicoil tap is pretty tough but an absolute nightmare if bust in head. (Granny teaching alarm sounds)

Doable with care...

 

[sump]

[sump]

Thanks for help and advice. Still not quite got the hang of this uploading!

Sounds like a delicate operation, maybe best to remove the exhaust but seems an awful lot of work just for a couple of studs.

[maxstu]

Early system l see. Best to remove silencer and pipe to that cylinder. It should not be too difficult.
Is it lower or upper fixing? Studs or bolts? I dont see a stud?
With pipe connected it is unlikely to get correct angle for drilling or tapping lower fixing anyhow.

[TONYT25T25]

Dreading this happening to me, but would think that removing exhaust would be best option that would give better access, has the stud sheared off flush where it goes into the cylinder head or is there some left in the exhaust, if so there may be room to remove it using a stud extractor tool.

[maxstu]

Ive done about nine re-drills and exhaust taps during ownership of three campers over 13 years. Three at the other end with engine in situ. Tough on the neck but not terrifying. Getting in a comfortable position is the key. Plus top condition drill bits. Even using pillows to support your neck and head helps.
Drill no deeper than 22-23mm.

[Mr Bean]

Wow! That says as much about the inherent frailty of the steel stud in aluminium as it does about your engineering stoicism.

But regarding your pillow support I too suffer from the stiff neck under the vehicle affliction but find that a four pint plastic milk bottle or five litre  plastic containers more supportive than a by definition  squishy pillow. However while the tops would pop off from the four pint bottle - I tried it, I would fit a replacement soft push in plug on the five liter container which could be forced out in an accidental crush scenario rather than allow your skull to be burst like a pumpkin in a shooting range. As you can see I am horrified to see people laying under vehicles which are unsafely supported.

[maxstu]

Wow! That says as much about the inherent frailty of the steel stud in aluminium as it does about your engineering stoicism.

Or despite lengthy ownership of T25's l still manage to buy duffers. lt mostly to do with engine replacements or exhaust upgrades to be honest.

As you can see I am horrified to see people laying under vehicles which are unsafely supported.

l agree. I've never felt comfortable working underneath while vehicle sits on drive-on metal ramps. But that's my failing not the ramps. It seem so easy for one ramp to go sideways. Not likely. Yet the thought blights task in hand. Besides ramps tend to leave vehicle lMO too high to work under when drilling exhaust studs on cylinders 1&3. So I made wood blocks from two by five roofing rafters. I included raised edges at just the right length so nice and snug against both side of tyre. I then add a trolley jack to engine support bar. This gives plenty of wriggle room under van

[sump]

Well Thanks for all the replies. 

The studs on that head had been replaced with bolts and the bottom bolt just fell out while in Henley at the trad rally. I picked up a new bolt from an exhaust centre and duly bolted it in but by the time we got home it was missing again! 
On further inspection I removed the top bolt and found that although a little loose in places the treads wer'nt actually stripped out just worn?
Fitted a new gasket and new bolts and managed to get it to hold. Bolts are still there to this day but it blows so obviously I just can't get enough purchase to nip it up enough.
Wondering now after all the replies if it could be possible to just re= tap the thread that is there?

[jrt]

I have used JB Weld Extreme Heat to hold a stud in before. It’s like a gritty paste you smear on the threads and works well.
David.

[TONYT25T25]

Trying to imagine the inability to nip it up enough because of either lack of thread available or other reason, is there room to add a washer to make up the difference of gap in thread and then allow the bolt to be nipped up a bit more.

[Mr Bean]

Well Thanks for all the replies. 

The studs on that head had been replaced with bolts and the bottom bolt just fell out while in Henley at the trad rally. I picked up a new bolt from an exhaust centre and duly bolted it in but by the time we got home it was missing again! 
On further inspection I removed the top bolt and found that although a little loose in places the treads wer'nt actually stripped out just worn?
Fitted a new gasket and new bolts and managed to get it to hold. Bolts are still there to this day but it blows so obviously I just can't get enough purchase to nip it up enough.
Wondering now after all the replies if it could be possible to just re= tap the thread that is there?

Yes that's a nightmare as to make the best use of the thread in the the head you would need to cut the bolt to a length which would not bottom it out in the thread or worse bottom it out in the head. This is one situation where the rule of 1.5 times the thread diameter of thread engagement is clearly questionable. Of course this would be tricky to get right for all eight locations. In fact the use of bolts in itself destines the thread to be "exercised" every time the exhaust is removed and replaced.
Due to this I avoid the use of bolts as studs once properly installed usually have no need to be interfered with and the steel to steel interface of the stud and nut is much more robust also the nuts at least can be replaced if corroded or damaged for good measure. I have found that proprietary studs provide a respectable thread insertion length. But by initially starting the tap gently with your fingers feeling out the existing thread and of course taking care not to break into the coolant section, you can find a often further few mm of thread-able hole.