Removing threaded exhaust from manifold

[mbowser]

I've started a rattle can rebuild on a Westerbeke W27 and I'm blocking off the winter to get this thing back in shape. The engine is out of the boat and sitting in my shop and the first order of business is to rebuild the exhaust manifold. Really the only thing that needs to be done is to replace the gaskets on either end, clean it up and repaint, but in order to do so I have to get the old exhaust pipe off that goes to the mixing elbow. I'm guessing it's galvanized steel and it's screwed into the aluminum manifold (I think it's aluminum). It's really badly rusted and of course it won't budge. I applied a bunch of PB Blaster and will keep at it for a few days, but I'm not confident it will free up.

Anyone have any tricks that I can use to get this free? Heat, hammer, bring it to a shop and throw money at it?

[deblen]

Since you have the engine out and in a warm workplace,plus lots of time-
Why not replace the old iron pipe with new black iron pipe & new black fittings. (Galv. just "burns" off under dry exhaust heat)
That means you only have to salvage the alum. manifold end plate.
or,if that plate is really as flat as it looks in pic,it may be easier to build a replacement for it also,using 5 or 6000 series marine alum. plate.
Cheers/Len

[Bowdrie]

Originally Posted by deblen

it may be easier to build a replacement for it also,using 5 or 6000 series marine alum. plate.
Cheers/Len

I think you're right, a new piece of plate would be of minimal cost.
Perhaps a bit thicker if stud length will allow?
OP, be careful with those studs that hold the end plate.
If they will easily come out and could be changed that would be great but take no chances at all of breakage or damage.
Perhaps just better to clean the threads with a wire brush, maybe run a die over them.
I mention that as you want the nuts, (new,) to easily tighten to make a leak proof joint without straining/risking the studs.
Use a good anti-seize paste on all threads, (Permatex).

[mbowser]

I think that picture might be misleading. The plate is just a cover for the coolant 'jacket' on the manifold. The pipe doesn't screw into the aluminum plate (that would be too easy), it is screwed into the extruded aluminum manifold body (underneath the plate) and it is corroded in good. I'm hoping I can get it out without destroying the manifold. I don't think this model manifold is made any more, so I want to be careful in my approach.

[deblen]

Originally Posted by mbowser

I think that picture might be misleading. The plate is just a cover for the coolant 'jacket' on the manifold. The pipe doesn't screw into the aluminum plate (that would be too easy), it is screwed into the extruded aluminum manifold body (underneath the plate) and it is corroded in good. I'm hoping I can get it out without destroying the manifold. I don't think this model manifold is made any more, so I want to be careful in my approach.

A pic is worth a thousand words indeed!
You may have to hacksaw the exhaust pipe off close to manifold end.
Then,use a mini hacksaw to slice the remaining threaded pipe stub lengthwise internally.That should let you collapse the old pipe,inside the manifold thread,with a cold chisel.


https://www.amazon.com/LENOX-Tools-M...9976818&sr=8-2


I have never used Permatex anti sieze,but I have had success with NeverSieze
https://neverseizeproducts.com/marin...-8-never-seez/

[jamhass]

Looking at the pic, I might suggest (as a first step) removing the nipple, leaving the 45 street ell on the manifold. You can then inspect the inside of the 45. If it is in good enough condition, you could leave it in place rather than risk the manifold. Then rattle can the heck out of it.

[mbowser]

Originally Posted by deblen

A pic is worth a thousand words indeed!
You may have to hacksaw the exhaust pipe off close to manifold end.
Then,use a mini hacksaw to slice the remaining threaded pipe stub lengthwise internally.That should let you collapse the old pipe,inside the manifold thread,with a cold chisel.


https://www.amazon.com/LENOX-Tools-M...9976818&sr=8-2


I have never used Permatex anti sieze,but I have had success with NeverSieze
https://neverseizeproducts.com/marin...-8-never-seez/

I'm afraid that that is the way I'm going to have to go if I want to get the whole thing out, but it seems pretty risky and I'm afraid that using a cold chisel to collapse the pipe could crack the aluminum manifold. I've been alternating heat and pb blaster for the past 2 days and it's still not even close to budging. I'm going to give it another day or so to see if the pb blaster works its way into the joint.

[mbowser]

Originally Posted by jamhass

Looking at the pic, I might suggest (as a first step) removing the nipple, leaving the 45 street ell on the manifold. You can then inspect the inside of the 45. If it is in good enough condition, you could leave it in place rather than risk the manifold. Then rattle can the heck out of it.

This is probably the safest route, the 45 degree elbow appears to be in decent shape. I'd really like to get in there to inspect/replace the baffles though.

I wonder if a machine shop with precision equipment would be able to tackle something like this?

[gonesail]

the hacksaw idea might be worth a try. maybe not the collapsing part .. a few cuts might help to release it .. but also could destroy the threads on the manifold

[Bowdrie]

Originally Posted by gonesail

the hacksaw idea might be worth a try. maybe not the collapsing part .. a few cuts might help to release it .. but also could destroy the threads on the manifold

Yes, requires steady hands and the patience of Job, one slip and ruined threads.
Might a shop that does Electro Discharge Machining achieve success?
A couple of times I've used a battery and jumper cables to break the bond of bolts that were frozen, but they were small sized and threaded into a relatively thin aluminum mast.
It's a process that's fraught with its own dangers, (you hope the battery doesn't explode).

[Madehn]

Get it where you can put a pipe wrench on the nipple with the body in a vice. Heat up the aluminum while you hold some ice on the pipe. T
Put a little pressure on the pipe wrench then hit the end of the pipe wrench with an air chisel in the direction you want to turn. The rapid shocks will help to break it loose. If you can avoid taking it off do so. Sometimes perfect is the enemy of good enough. Good luck.

[NorthCoastJoe]

If you cannot live with leaving the elbow. I think the best would be to leave it to a machine shop. But even they might mess it up. Do you have enough room to bump up one pipe size in the aluminum?

[Oldwheels]

Al expands 3 times as much as steel, Try heating the housing with a butane torch.
Bottom line this is a bad mix of materials.
Cutting it out I would use a dremel with a carbide bit. Hack saw is hard to control. Slow and carefully.
Consider replacing with Al pipe

[Bycrick]

I have the same exhaust manifold on my Genset. I constantly had problems with the end plates leaking because of the gasket between the aluminum manifold and the steel end plate. In 2005, I rebuilt the Genset and replaced the OEM steel end plates with ones made of 1/4” 6061 aluminum. They’re still there, no leaks since.

[wyb2]

Originally Posted by mbowser

I'm afraid that that is the way I'm going to have to go if I want to get the whole thing out, but it seems pretty risky and I'm afraid that using a cold chisel to collapse the pipe could crack the aluminum manifold. …

Leave a little bit of pipe, don’t cut it totally flush with the manifold. Cut 2 slits maybe 30 deg apart, then hammer inward on the exposed lip between them. Don’t try to use the chisel as a wedge between the iron and aluminum.

Once the strip between the slots is bent in and removed, the rest will likely unthread. If not, just keep taking out strips.

This worked for me on a flange that bolts to the engine header manifold. It was steel, not aluminum though.