Help! Breaking free an exhaust manifold

[Cap Bill Des]

We're trying to install the alternator bracket upgrade on our Universal 25. The studs on the exhaust manifold were not long enough to simply bolt on the new bracket. So we need to remove the studs and install the longer ones in the kit.
All the nuts came off easy on the existing studs. In fact two upper studs came right out with the nut(!).
This encouraged me to try getting the other studs out with doubled nuts . Mistake! The first stud I tried sheared off right where it exits the manifold.
So now we're trying try break the manifold free to slide it off. The manifold has broken free at five of the six studs, but will not come free on the stud that sheared off. We have opened it up perhaps 1/64"- we can see the stubborn stud at the block/manifold joint

We have tried:
- putty knives and screw drivers as wedges.
- pb blaster both on the sheared off end and down in the 1/64" gap
- 2 minutes heat gun at the joint.
- a Dremel tool on the sheared off end in case a burr was holding the manifold from sliding off
- drilling the sheared off end- worked up to 5/32"on the just under 8/32" stud ( actually 6mm or about 0.240)

How do we get the manifold to break free at this last stud? ( It is the upper forward stud)

Please help!! We're living on board and dead in the water now in Hampton, VA.

[AndyEss]

Not sure why you needed to remove the exhaust manifold for a new alternator bracket, but if I were you, I would continue drilling that last stud out - there seems to be a bit of meat left (5/32 vs 8/32). I bet it gives with another 1/32 -3/64 of drilling.

[wingless]

Welcome to the forum.

The parts manual for that engine shows six studs retaining the exhaust manifold to the cylinder head. The cylinder head is shown on page 10.

Are all six studs disconnected or snapped off?

Be careful to not damage the gasket surfaces. Screw drivers used as wedges will damage the gasket surfaces.

My guess is that the gasket is acting like glue, retaining the parts together.

A lever between the manifold and the cylinder head might help induce separation of the parts. A block of wood to spread the force could help avoid cracking the parts.

A putty knife forced into the gasket joints might be required, but that should be the last step.

[David M]

As a last resort, you may have to remove the cylinder head and bring it in to a machine shop.

Have you tried applying heat?

[Cap Bill Des]

Hi, this Bill, the OP. Thanks for the responses

Andyess-. My drilling so far is not perfectly on center, which is why I stopped at 5/32. Maybe I could steer my hole back to center if I start back with a small drill at an angle- and then I could work back up in size.
Does anyone know the risk or impact if my drilling is not centered, and I bite into the manifold casting? Isn't the stud in its own hole, with walls separating the stud from coolant and exhaust?

On the idea of heat- we were thinking of getting a 1lb green propane bottle and a torch tip. Is that what you mean? Is it ok to apply this heat to the joint between block and manifold? We already have the 1/64" gap, and can see the stud. Thank for any and all advice!

[AndyEss]

I kinda figured that your drilling wasn't able to be done perfectly straight and centered.
I think your thought that you have a burr on the end of the broken off stud is right, and the dremel didn't quite take it off. Maybe some of the dremel cuttings even jammed into the slight stud clearance.
There should be appreciable manifold wall thickness around that stud hole so that the studs can actually be loaded to hold tthe manifold in place.
What is the manifold made of? Cast iron? Aluminum?
See if you can figure out the thickness of the manifold at the stud. Drilling the broken off, probably burred (and rusted) stud shaft a short distance into the manifold might get rid of the burr and allow the manifold to,slip off. As long as you don't bite too far into the manifold wall, slight nicks shouldn't be fatal.
The heat option is probably the first thing to try. Make sure you have some firefighting precautions in place to deal with the PB Blaster fluid catching on fire when you first hit it with open flame. Same thing for prepping any burning drips falling from the manifold into the bilge.
Another thing that might be binding that last stud is carbon buildup from an old, slight exhaust leak around that stud.
I bet with a little more finesse you will get that manifold off in the morning after a good night's sleep. Don't work on it tired - that's a sure way to screw something up.
Good luck, and let us know your progress.

[jimbunyard]

If memory serves, there're no locating dowels for the manifold. If you can tell that all other studs are free from the manifold, then attempt to remove them. Chances are very good that all will come out, in which case you can rotate the manifold itself to break free the remaining stud (in the head) and, if you have to, break or cut it at the manifold/ head interface. Once the manifold and head are separated, there'll be less of a problem removing the broken stud from the head, and either driving or drilling the broken stud from the manifold.

Given the thermal mass involved, an electric 'heat gun' is useless in this application; even an ox/acetylene flame would likely be ineffective, and could result in more damage (though in the correct hands it could also solve the problem...).

Methodical patience is the key in this situation...

[Cap Bill Des]

This is Bill, the OP, again. A good night's sleep (while PB Blaster soaked) and we're ready to go again....

First, some answers to questions:
- the exhaust manifold is cast iron
- the status of studs:
The two upper rear studs are completely out- they came out with the nuts
The three lower studs are still in the block, nuts off, and the manifold has clearly release from the block in those locations- can see movement. It
The upper forward stud is in the block, nut off, sheared off where it exits the manifold.

Given how easily the manifold released at the other studs, we do think a burr on the sheared stud is the holdup.
Plan this morning:
- see if PB did magic overnight
- get propane torch on broken stud
- lastly drill more on sheared stud
Idea is simple first, then escalation.

Is it also ok to use torch at block/manifold joint where we can see the stud through the 1/64" gap we have?

We are hesitant to try removing the other three studs still in place- only way we know would be double nuts- because that method sheared the first stud I tried! The idea of being about to rotate the manifold to break free last stud is attractive, but afraid of ending up with multiple sheared studs.

[Cap Bill Des]

Photo

[wingless]

Thanks for that image.

Could an image please be provided showing the surface where the stud broke off and the fragment is preventing movement of the manifold?

[Cat36Mahalo]

If the stud snapped you you’ll still be able to pull the manifold. You also need to remove the three nuts holding the exhaust to the manifold.

[Cap Bill Des]

This photo shows the status of all six studs/ holes on the exhaust manifold. Another photo in next post will show magnification of sheared stud

[Cap Bill Des]

This is close-up of sheared stud. You can see my off-center drilling and also earlier Dremel work on surrounding surface when we first thought of maybe a burr.

Yes, the exhaust flange and riser have been removed in the back...

[wingless]

Thanks for the images,

The broken / drilled stud appears stuck to the manifold.

Why not try placing a drift against the broken stud face, or drilled hole, then use a hammer to impart impact force to break them free?

[jharding]

it would be my guess that the stud is corroded to the manifold, heat and shock are your best friends. You need to heat the manifold around the stud to get it to expand and break the corrosion and give it some shock while you have pressure on it. a punch on the stud may do it but you don't want to swell the end of the stud. tapping the manifold all around the stud when heated and with pressure on it. I have heated cast iron manifolds till cherry red before and never hurt one, this having a water jacket might be a little more fragile. be careful and you will get it off.