I've read this thread with interest because I have handled this kind of problem many times. It is aluminum oxide having migrated molecularly into the threads to create an unbelievable grip. It is also so tight that it is nearly impossible to soak any kind of penetrant or lube into it because it isn't very porous. It would be interesting to see some cross-section views of all of these methods to see how far the penetrating lubes were able to get.
I've almost always had to drill out and retap. Sometimes when the drill has exposed some of the threads those other solutions can get in to do some chemical work.
And on the idea to use air-pressure on a stuck piston out of a cylinder head, I just want to chime in against it as too dangerous. The same effect is better done hydraulically with better results and less explosion and less flying pieces of metal bouncing around the shop.
I'm trying to free a stuck cylinder on a
motorcycle. Its aluminum cylinder held on
with four studs.
One of the (4) studs is seized to the
aluminum. I tried Kroil, is there anything
better than that crap?
Have you tried the thermal trick? Try applying heat with a propane torch to the aluminum while the end of the stud is in ice. Mebbe the temp differential will be enough to unstick it.
Heat and dry ice saved the day for me once.
The problem is, the studs are recessed
below the cylinder deck.
I made a puller using a 1/2" steel plate and
a port a power. I heated the f--k out of it
with an oxy-aceteline rig, still no dice!
One of the old trick to remove aluminum heads on the old flathead engines that had corroded was to pour coke on the studs and let them sit for a while. The coke would eat the corrosion that had formed in the hole and on the stud. With a little tapping and some heat they would release and the head could be removed.
Kroil is the best penetrating oil out there.
Hope this helps,
Another old trick is to heat the stud, touch it with beeswax and unscrew. Good trick, won't always work-but I know of NO trick that always frees dissimilar metals.
Kroil- High on my list of liquid wrenches.
I hear rumors that ammonium hydroxide solution (such as Bo-Peep or Parsons brand "ammonia" sold at the grocery stores for cleaning) is the slick trick for freeing corroded aluminum. It's supposed to break down the corrosion byproducts.
I'm fond of kerosene as a rust penetrant. I'm fond of kerosene for a lot of uses, come to think of it. If they made women's perfume from it, I'd spend more time with my wife, and less in the shop. Seriously, I wouldn't let her out of the bedroom except to eat and bathe.
You could always pour Castrol Super Clean on the head. That'll dissolve the corrosion, and the HEAD. Poured some in a Coke can one time, just to see. 15 minutes later, the can was Swiss cheese.
I'll have to try ammonia.