Disaster strikes again..

[Bigbaldybloke]

I have ordinary steel cap head bolts with plenty of copperslip on them and plain plus spring washers. Easy to fit exhaust manifold with engine undisturbed if necessary. Had them for years, no problems. If you have a stainless manifold then stainless with stainless washers would probably make sense.

[alan.barker]

I always stay with studs that have been assembled with copperslip.
If you fit screws/bolts you risk stripping the threads in the Head. This is because when you remove the Head you are always winding screws into the threads in the alloy Head.
The Manifolds often need springing a bit for the tapped holes in the Head to line up and you can start to wind the screws in out of line. Each time you force them in you damage the threads in the Head
Alan

[Chancer]

The last thing i would want to see is the Cylinder Head damaged ana you get fed up with your +2.
When the Cylinder Head is at the Machine Shop i suggest that they remove the Exhaust Studs also.
Then you can fit new Exhaust Studs and screw them into the Head by HAND with lots of Copperslip on the threads.
Assemble Manifold with spring washers and BRASS NUTS.
Before you fit the Head make sure all the Studs screw into the Head by hand the full depth.
Fit the Head WITHOUT the Studs so they do not get in the way with the Exhaust Manifold.
Sorry to tell you how to suck eggs but after 45 years working on Twin Cams i am starting to know the ropes
I hope your Heath Robinson bodge holds out during the drive.
Alan

What do you do to ensure that on removal that the nuts come off and not the studs winding out of the head?

Or is it that to remove the manifold in situ the studs need to be removed? If so then I cant see the opposition to bolts.

My natural reaction would be to locate the studs with loctite to ensure they dont unscrew (the studs can still be removed with heat) but maybe the close proximity of everything prohibits it.

[alan.barker]

When you undo the brass nuts they do not wind the studs out because the studs have been tightened in the Head.
To tighten studs in the Head you use 2 half locknuts on the exposed threaded section. Lock one nut against the other using 2 spanners. Screw in stud using your fingers then use spanner on outside nut until it locks. Unlock the 2 nuts using the 2 spanners and remove with your fingers. Put in place spring washer then brass nut.

Once the brass nuts have been removed you can unlock the stud by using your 2 locknuts. Then screw out with your fingers causing no damage to the threads in the Head.
The point is using studs when you tighten the Manifold to the Head all stud threads are fully engaged in the Head.

At no time you risk damaging the threads in the Head.
This is only my personal way of working and if you have found a different way that suits you why not.
Personal choice
Alan

[JonB]

My view, Alan, is that I will try and keep the car original, so studs for me.

However I do have a question - do the studs make it that much harder to remove the manifold or head (due to reduced clearance)? I have a Spyder chassis.

[rgh0]

Take the head off if you wish .

i would not and it is not necessary. You say the drill went all the way through before it broke ? The get a suitable pin punch and tap the drill out and keep drilling. i dont see the problem ?

If you cant do that start another hole beside the drill that broke. I assume you are actually using small drills of maybe 2 mm size currently and not trying to drill out a 6 mm stud with a 5 mm drill in one go? Hard to imagine you managed to break a 5 mm drill.

Another alternative get a dremel if you dont have one with a small carbide bit and take out the bolt and drill carefully. Or at least cut a slot in the top of the bolt so you can get an impact driver on it and head the allow cool the bolt hit it with an impact driver to see if it moves.

Patience and care is what it takes. i would be more worried about a machine shop butchering the head personally.

What you replace them with is up to you but read a few good books on bolted joint design first before you start carrying out advice on modifications to bolted joints you may not understand the consequences of

cheers
Rohan

[MarkDa]

Does the tapping go all the way through to the waterway?
I thought it was blind - to reduce corrosion?

I managed to snap a 6mm bit in a k
(Non Lotus) brake caliper bleed screw once - it was in situ and I must have gone tight thro ugh and snatched at the drill.
I was not a happy chappy, I couldn't believe how careless I had been.

[JonB]

Take the head off if you wish .

i would not and it is not necessary. You say the drill went all the way through before it broke ? The get a suitable pin punch and tap the drill out and keep drilling. i dont see the problem ?

Hi, Rohan. Pardon me for not understanding, but how do I tap a drill out from above with a pin punch? I'd be driving it further in, surely. What I didn't say is that I attacked it again with a different drill but the result is a bowl with no part of the jammed bit showing.

As to removing the head, it is on the to-do list anyway because I have quite a bit of oil coming out of the timing chest gasket.

If you cant do that start another hole beside the drill that broke. I assume you are actually using small drills of maybe 2 mm size currently and not trying to drill out a 6 mm stud with a 5 mm drill in one go? Hard to imagine you managed to break a 5 mm drill.

It's a 3mm bit I think. I had been drilling with a 5mm bit but it was off centre so I tried with a smaller bit. I only drilled a couple of mm down with the bigger bit, so I think there is still some undisturbed thread.

Another alternative get a dremel if you dont have one with a small carbide bit and take out the bolt and drill carefully. Or at least cut a slot in the top of the bolt so you can get an impact driver on it and head the allow cool the bolt hit it with an impact driver to see if it moves.

I have a Dremel but no suitable tip. It's one of those "get 150 accessories" type things that has very little of what you actually need. For example, there is one drill bit (3mm) and one reaming bit. The carbide tip you are talking about, is that a drill bit or a stone grinding tip?

Patience and care is what it takes. i would be more worried about a machine shop butchering the head personally.

I think I have demonstrated that I do not possess vast stores of patience.

You're right about the machine shop, so I might have another go at it with the Dremel.

What you replace them with is up to you but read a few good books on bolted joint design first before you start carrying out advice on modifications to bolted joints you may not understand the consequences of

I think it is fair to say it's not a safety critical joint. To my mind, if a bodged up external bracket (with a degree of flex in it) is able to exert enough pressure on the housing to form an effective seal at operating temperature / pressure, any replacement that can do the same should suffice. But.. I'm not an expert!

[JJDraper]

FWIW I have a similar, but reverse problem pending.. One of the studs has pulled the top two thirds or so, of the thread out, leaving a little thread at the bottom of the tapping. I have been very wary of tightening the stud too much and pulling the rest out, but so far so good (10 years). To help matters I use a cometic gasket from Burtons, which is a foamed composite gasket with an ally core. It allows me to get a water-tight seal with less tightening as the compound seems to take up irregularities in the surface. I suppose I should really get the tapping Helicoiled..

The gasket is nearly three times the price of an ordinary gasket, but even so is only a few quid, and its re-useable.

Jeremy

[Chancer]

When you undo the brass nuts they do not wind the studs out because the studs have been tightened in the Head.
To tighten studs in the Head you use 2 half locknuts on the exposed threaded section. Lock one nut against the other using 2 spanners. Screw in stud using your fingers then use spanner on outside nut until it locks. Unlock the 2 nuts using the 2 spanners and remove with your fingers. Put in place spring washer then brass nut.

Once the brass nuts have been removed you can unlock the stud by using your 2 locknuts. Then screw out with your fingers causing no damage to the threads in the Head.
The point is using studs when you tighten the Manifold to the Head all stud threads are fully engaged in the Head.

At no time you risk damaging the threads in the Head.
This is only my personal way of working and if you have found a different way that suits you why not.
Personal choice
Alan

Alan.

That is the way that I have always done it and would have done it so we are singing from the same hymn sheet!

Its just that in the past working on British cars I regularly found that factory fitted brass nuts would gall on removal and at least 50% of the time the stud would unwind, perhaps they had not been properly fitted but they were into steel and not aluminium and had not been fitted with Copaslip.

It was probably corrosion on the exposed threads and incorrect original assembly. Good to know that when done dilegently your way the brass nuts remove without a problem.

[MarkDa]

The early manifold nuts were those terrible 'self stripping' locknuts weren't they?
I've always found that standard deep brass nuts with a spring was have done the trick on manifolds of all types.

Yes with a good gasket (or even sealant) you can normally get a watertight joint without too much load.
It's not a bolt you need to pull that often so Jeremy's 1/3 bite should do another 10 years.
I guess that if it does eventual strip then helicoil is the quick and easy solution.

[pauljones]

Jon,
Can you get a smallish chissel in there without damaging it?
Im thinking gently tap it on the 3 and 6 o'clock points and see if that helps turn it.

After re reading this, have you drilled in center with a 1mm drill?

[Bigbaldybloke]

JonB, you've had almost every suggestion possible apart from doing a dance round it and praying to a pile of chicken bones!
I'd leave it be until you have time to take the head off and take it to a proper engineering works, not a backstreet garage or some other place, a proper engineering shop with all the right machines. They will be able to clamp the head on a rigid table on a milling machine and with an end mill, carefully mill out the remainder of the stub in there, if it ends up going oversize they can helicoil it or if necessary you can probably go up one size on the bolt and drill out the thermostat cover to match if you have to go this route. Absolute worst case a sleeve could be made up, and pressed and welded in.
I used to work in the gas turbine industry and we if drilling didn't work, we milled out broken bolts / studs or spark eroded them out, depending on size, location and the materials involved.
If the head is in a really bad state there are some excellent welders out there that could repair it, a friend has recently come off his AJS motor bike and it slid down the road on its crankcase and wore a hole right through it. This has been weld repaired and re-polished and you would not know it had happened, so anything is recoverable.
Many years ago my Hillman Imp head cracked on the water jacket between cylinders 2 & 3 and this was successfully welded up - it was a polished and ported race head so I didn't want to lose it.
So don't despair, as they said in the film "It will be alright in the end, if its not alright, its not the end!"

[2cams70]

There's no doubt it can be successfully repaired. In the very worst cast (which I'm almost certain we are not looking at here) a "Time-sert" or "Ful torque" thread insert can be installed to return the threads to original size if the hole is too far oversize for a standard Helicoil. I'd do this in preference to using an oversize bolt.
The key to a good job is to have everything held firmly in perfect alignment and location before machining. It's virtually impossible to achieve this with the head in place on the car.
We also need to look at what caused the problem originally. What's happened is that there has been a slight leakage of the gasket between the opening for the thermostat and the fixing bolts. which has caused the threads to corrode. This leakage was probably not enough to be visible from the outside. Usually it's incorrect or uneven torquing of the bolts that causes the failure. I'd suggest in future some low strength loctite to seal the threads from coolant leakage or as another poster has suggested maybe using stainless steel bolts.However I can't comment on these specifically because I've never used them - maybe the galvanic effect of the different metals has a detrimental effect over time??

[2cams70]

Sorry forgot to add, if there's a Helicoil you should not use loctite - ok with "Time-sert" or "Full-torque" insert however.