Help! Breaking free an exhaust manifold

[jimbunyard]

The studs only rarely lock in the head; it is much more common for them to rust into the manifold.

If you're sure that the lower three studs are free, it is worth an attempt to remove them with vise grips or double nuts (with vise grips you'll likely have to replace them). They are thin and fairly flexible; they'll twist probably an tenth or so of a turn before breaking, much more than 12-15 ft lbs is too much.

If you can put tension between the head and the manifold and heat the boss that the stud runs through from the inside of the manifold, you might do some good.

Mapp gas is better than propane, don't worry about heating anything up too much with either. Sometimes several heating and cooling cycles will loosen things up.

I would leave drilling as a last resort, only after the manifold has been removed. It is difficult to drill a stud out on the bench; as can be seen in the picture you're already well off-center, and things are not likely to improve...

[Cheechako]

Originally Posted by 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?

^^ THIS. Have you tried this? You need to shock it and break free that rust etc. Chemicals are a waste of time. Is there any gap at all between the head and manifold? if so, wedge some flathead screwdrivers in the gap top and bottom. With a sturdy drift punch, hit that stud hard!

[boatman1]

I believe that I’d try wooden wedges, assuming there’s room to get them into the gap betwixst the manifold and the head. Least likely method to crack an iron casting. It takes a lot of heat to be effective, and that’s a precarious location to be using a torch.

[jimbunyard]

Originally Posted by 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?

Originally Posted by Cheechako

^^ THIS. Have you tried this? You need to shock it and break free that rust etc. Chemicals are a waste of time. Is there any gap at all between the head and manifold? if so, wedge some flathead screwdrivers in the gap top and bottom. With a sturdy drift punch, hit that stud hard!

Even if the opportunity wasn't lost by attempting to drill the stud, thereby leaving an uneven 'impact surface', this is a singularly bad idea, and is likely to peen the end of the stud, locking the stud into the manifold.

There is also the possibility of cracking the boss that the stud passes through, which would be manifold-replacement time...

The only relatively safe force that can be applied here is by inserting a wedge (an old wood chisel or a shallowly ground [20 -30 degrees] cold chisel) between the head and the manifold directly adjacent to the frozen stud and tapping the chisel lightly with a 2 lb or so hammer. If the boss can be heated from inside before and whilst tapping, (and, if I remember correctly, the forward boss can) so much the better...

[appick]

Hammer, bigger hammer like a 5-10lbs dead blown. Also a oxy acetylene torch. Heat it up until it's glowing red then pour some water on it fro. A hose or cup. If it doesn't come free the first time repeat. It will eventually come free.

I was a mechanic in Michigan and saw some serious rust on brake and suspension parts. The worst was old brake lines. The customer only needed a new wheel cylinder, but if you didn't take the time to heat and cool the brake line nuts you'd shear the line in half turning the nut. You could turn a $200 brake job into a $1200 full brake line replacement if things didn't go well. Learning to apply only as much torque as small fastners can take is a skill that comes with years of practice. Once you learn how to tell when the bolt is stuck and merely twisting you can STOP, as breaking it only makes things harder. Heating it and cooling it causes the expansion and contraction that will break the rust bonds locking it in place.

Some fasteners you can soak for months and the oil will never get to where it needs to go. A few quick heating and cooling cycles and off it comes.

Now if you don't have or can't find a torch set a yellow portable torch is your best bet. They burn hotter than the propane, but not as hot as the oxy acetylene torches.

Good luck!

[a64pilot]

You absolutely sure there isn’t a hidden nut somewhere?

[Qayaq]

How about a junior hacksaw blade between the head and manifold, try to keep the blade in the gasket as you cut. Then punch the stud out when you get it on the workbench

[Brewgyver]

It is FAR better to get the manifold off without cutting the stud. Sure, punching the the length of stud out of the manifold may be easier at that point, but then you're faced with removing the threaded end of the stud from the cylinder head, which may be difficult, as well. This is an OLD engine we're talking about here!

Bill (OP), you might want to ask this question on the Catalina 30 group, lots of M25 owners on there.

[NorthCoastJoe]

Looks ugly, agree with Appick. Can you slip a hack saw blade in between head and manifold ? You most likely will have to drill out the studs from the head anyway. I would say oxy-acetylene torch with a rose bud tip. Fast heating,looks like you have to heat more than one stud. Then wooden wedges and big hammer. Up state NY we worked on cars with a torch in one hand and wrench in the other a lot of the time.

[ferrailleur]

Originally Posted by 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.

Yes, there was a recall by Universal to replace the inferior original alternator bracket (prone to break up) with the one the po is installing

[NYSail]

Originally Posted by 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.

Careful about the pb blaster on your engine. I wouldn’t touch the stuff near engine. If it gets on gaskets it will destroy them..... then you’re looking at more tear down.

Good luck
Greg

[captlloyd]

My understanding is that there is a gap between the manifold and head. Try tapping the manifold back towards the head, then wedging it back out. Back and forth with liberal Blaster. Heat helps. Any movement is success, may take a lot of back and forth and try to tap on the strong portions of the manifold like corner areas. Tap just enough to move manifold.

[jimbunyard]

Lots of interesting ideas, hope he's gotten it off by now.

If not, some pictures of one I did a couple of years ago. Whilst the manifold was only slightly stuck on, as can be seen in the pictures the end plate was firmly rusted in place. After cutting off the nuts, it was removed with no heat and no heavy pounding, just a wood chisel, large flat screwdriver, hammer and after the plate was off, the studs were removed with some PB blaster, vise grips and a stud remover.

[Cap Bill Des]

Hi, this is Bill again, the OP.

Well, another pretty long day, and I'm not sure if we've gone forward or backward.

After reading all the great input we decided to:
A -Stress the joint between head and manifold with three wedge screwdrivers right around the stuck stud
B- Direct the torch right down the pressure cap opening on to the "rib" of cast iron that surrounds the stud ( it is the front upper stud, directly under the cap
C- After 2 minutes we started tapping the outside of the manifold.

The plan was to do this process every 10 minutes and hope the thermal cycling would break the bond between stud and manifold.

Getting ready for just the second cycle I was tapping on the screwdrivers...and bang!,. The stud broke at the block/manifold joint.

So...
We have the manifold off with this stud in it. We tried a little more heat and banging on a cement curb, but it is not breaking free.
We also have a stud broken off about 1/16" deep the the head(which is on the engine)

What to do? I'm not experienced at this, so I've got a call out to a recommended marine diesel shop to have someone come out and remove the broken stud. There is very good access and room to approach the stud. I guess we'll see in the morning.

On the manifold- do I just take it to a machine shop and have them drill the stud out?

I'm really hoping we can save both the head and manifold.

Thank you for all the help so far, I have been very pleasantly surprised at the depth of knowledge offered up. I just hope we can get this motor back together, and not have to spend our whole summer cruise stuck in one spot!

[wingless]

Progress?

Put the loose manifold into an ice box for an extended time.

Remove the ice cold manifold and use a MAPP torch to safely / quickly heat the area around the broken stud, but not the stud. Heat both sides of the manifold.

Quickly use a hammer and small drift, looks to be about ¼" diameter to knock out the broken stud.

For the broken stud threaded into the block, I've had VERY good results using this Irwin Hanson 11119 10 piece extractor and left hand cobalt drill set. Many times I have success just from the left hand drill bit and don't even need to use the extractor.