Where to apply the heat

The aluminum block. The thread ID will get bigger.

--Winston

The aluminum will expand more than the steel. Heating and cooling the aluminum a couple of times while adding some liquid wrench will work.

John

Apply heat to both, but dab some soap on the aluminium to be sure it doesn't get too hot and turn into a puddle :)

DAMHIK, OK? The soap will blacken a couple of hundred degrees F before you get to the melting point, useful to know...

Once all's hot, wrap a wet rag around the steel pipe (to cool and shrink it) and wrench away, brother.

Dave H.

My two cents:

Mis-tuned engines often times have the exhaust pipe go cherry red without damage to the engine when they are re-tuned properly. The binding of the exhaust pipe is caused by iron and aluminum oxides which have greater volume than the original metal, so they bind up the joint. I would heat the exhaust pipe cherry red (or as hot as you can get it) and then twist it off with a pipe wrench. Oxyacetylene torch preferred. When the steel pipe gets hot and goes soft the binding forces should be less as the pipe wall becomes less strong. I would worry about warping the head if too much heat is applied to the aluminum block. Good luck.

If you are heating with a hardware store propane torch, I doubt that you will have much success because the aluminum pulls the heat away from the place you need it too fast. As another poster said, you need an oxyacetylene or oxypropane torch. Remember that aluminum melts before it glows. I liked the "soap trick" from another poster.

In my somewhat limited experience, I have found that steel stuck in aluminum is about as bad as it gets.

Do you HAVE to remove the pipe? Would it be possible to cut it off a little (if necessary) and thread it and then go from there?

A 1" pipe has a pretty thick wall and would be hard to "peel", I would think.

Maybe swallow your pride and take it to an engine shop?

I'd sure like to hear your eventual solution.

Pete Stanaitis

snipped-for-privacy@aol.com wrote:

You might try running the engine to warm the block and then apply cold water to the pipe to cool it rapidly.

Please ley me know if you are successful. I've got over a hundred galv. steel pipes threaded into AL irrigation pipe. I have yet to remove one without taking all the AL threads out with the steel.

Now, my son is purty good at building up the damge so i can mill and re tap.

Karl

And a suggestion, keep a damp rag on the pipe to keep it from heating up.

The block is what needs to get the heat. I'd probably heat it in an oven, if available. Or atop a wood-burning stove. Or a hot-plate with a piece of steel plate between stove and block.

As someone else suggested, several cycles over a day or two, with penetrant introduced during the cool-down cycle (below the flash point of the oil)

You're not in a hurry, right?

Rex

That's what anti-seize compound is for, Karl... JR Dweller in the cellar

Karl Townsend wrote:

JR,

Since this is a daily issue for me now, (stainless and aluminum), what is a good anti-seize compound?

A little more info. This is a transplant from a fire department water pump to a vintage garden tractor. It is a flat head engine; the individual exhausts point straight up. To fit correctly on the tractor, there are tight 90 degree ells I must install to fit the OEM muffler.

Pete: I have plenty of fire power, OA torch. I just remembered I also have a jug of R22 that would cool the pipe better than a wet rag. (There is a memory for you guys that have installed Chevy rocker studs.)

Rex: This is a pretty fair engine. I'd rather not overhaul it just now. I'm sure that much heat would take out all the seals.

I have two cylinders. If one method doesn't work, I'll try another on the other side. I have a tap so I can chase the threads if need be. I have to be careful and not crack the threaded port out to the stud holes. If I had a flange mount exhaust system that would fit, I wouldn't worry about the threads. We will see how it goes.

Thanks for the ideas.

Denis G. wrote in rec.crafts.metalworking on Tue, 12 Oct 2010 05:50:56 -0700 (PDT):

I would be concerned about the AL threads reaching the 'hot shortness' point if the steel pipe is red hot.

A:

The latest tests I've seen favor a 50-50 mix of acetone and ATF for loosening threaded bodies. I'd leave the threaded joint in that over night. A little vibration in the pipe wouldn't hurt. Just a thought, but if you have an electric engraver, you might want to band clamp it to the pipe and leave it running there awhile after applying the above solution. A series of reasonable wallops with a deadblow hammer might also fit your repetoire.

If you have any liquid refrigerant, you might use that to spray the pipe. And putting a cloth bag of ice on it and inside of it for cooling wouldn't hurt either when you are heating the aluminum.

Keep us posted on the process.

Regards,

Edward Hennessey

Dan, you might be right, but there are a lot of unknowns. How much of the aluminum threads are actually left? My idea was to soften the steel to allow the pipe to collapse a bit and reduce the binding forces. I've removed some solid steel exhaust studs sucessfully by heating the studs red hot and wiggling them back and forth, but maybe I was just lucky. It would be nice to see an academic paper (with cross section micrographs) on this topic and an explanation, but it's not easily available to me. Where's a corrosion expert when you need one?

Face it, you were lucky...

Yes.

There are specific dopes that can be used. some people report success with Staylok and I've had good luck with 3M 5200.

as I'm sure you know it is an electrolytic corrosion so insulation is the name of the game. Cheers,

John D. Slocomb (jdslocombatgmail)

Okay. Here's what I'd do: Saw the pipe off flush with the block. Mount block in mill. Bore out pipe until threads start to show. Pick or chisel out threads.

Pete Stanaitis

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snipped-for-privacy@aol.com wrote:

I pictured a bare block with a pipe sticking out of it, sorry. I'll fall in with the heat/cool cycle on the pipe with penetrant added.

You might fill a bucket with ice water and salt and suspend the engine over it with the pipe emmersed in the fluid