Frozen motor - melting out pistons

Ab4875

Ab4875

Senior Member
I've got an old 8BA motor that's been out in the elements for several years with the heads removed. Its pretty close to junk but I want to salvage the conrods. The pistons are aluminium and are stuck. I've tried soaking in penetrant for a few weeks without any success.

I was thinking of trying to melt out the pistons with a gas torch. Has anyone tried this?
 
If you heat up the pistons you will just expand them. You would have better luck if you could fill the block up with very hot water. Have you tried the 50% acetone 50% auto trans oil for the penetrant? I think I would drill a lot of holes in the pistons and break most of the large pieces out to reduce the friction enough to move the crank. Too much heat might not be good for the small end of the rods you want to save if you used an acetylene torch. Just a few thoughts.
 
I have pulled a few engines like that apart,the trick if you want to save the bore or the rods is to use a 3/4 diameter bar about 2 ft long,then turn one end down to about 1/2,then from the top or the bottom of the pistons use a 2 lb hammer and smash the pistons apart,it works
Lawrie
 
Have you an engine re-builder handy? With a 'hot tank'? Simply drop the block into the hot tank and let the pistons dissolve!!
 
Since you've soaked it take the crankshaft out. Get a piece of wood about the size of the bore and stick it into the cylinder. A big hammer should take care of it, probably without breaking anything. Watch that you don't drive the rod into the ground. You just need to get the piston moving with the hammer then you can be more gentle.
 
Bonus Built Acres said:
I have gone this route a few times,
just watch the pilot bit so you don't drill too far into the connecting rod end... :D I've heard of that happening anyway, not that I'd know, :rolleyes:
Click to expand...


In other words have another shorter pilot bit for the big finish.

Lonnie
 
I soaked a L=head Dodge engine for a long time...couldn't move it either...I was however, able to drop the crank.

I had a 3/8ths slug of metals I had cut at some point, and fit inside the bore...now the Dodge pistons were flat. so I took my air chisel and fashioned a blunt blade for it, and rattled the piston to get it moving, then wood and a hammer got it out.
 
I've tried getting the crank out of some stuck motors, but the problem I've had is you can't get to some of the Rod cap bolts due to their position. I've tried turning a hard to reach one and rounded off the corners.
So far lots of soaking and a good piece of hardwood and a big hammer have worked best for me.
Although I do know where there are about a dozen flatheads sitting in the dirt in a junkyard that would be a lot worse than any I've torn down.
I could probably get them all cheap, but I'm not sure I have enough time left to take on such a task:)
 
Pops built a special drill guide that allows you to punch a series of holes through both the piston and rings to free things up. Once the tension is released from the rings the pistons often come out pretty easily. If not, you can always chip away at them with a cold chisel and carefully work them out that way. I'll see if I can grab a photo at lunchtime.
 
I had to use a cold chisel on a motorcycle motor once, after I busted out the piston it was as if the rings were welded to the walls.
 
i bought a ancient 1 cyl hit and miss engine that was stuck bad.thied everything.an oldtimer told me to stand cyl on end pour brake fluid ib it and a stick uf wood maybe1x1 light the brake fluid let it burn all day just keep topping off the fluid through the day.at end of day took a 4x4 and the piston came out.never hadto do a v-8 but maybe u could do 4 cyls at a time.it heats the block slowly and evenly.this block was probably350 lbs bare.i worked at this thing for a week before triying this.i was sooo happy.no damage.dit have to sleeve it due to rust.
 
A few months ago, I acquired a stuck 1938 Lincoln Zephyr V12 that was stuck.
I mixed up the acetone ATF mix and soaked it 1st from the top, then from the bottom, but after weeks of soaking, no luck.

Next, I filled each cylinder with acetone and set them on fire. Repeated this numerous time and was eventually able to disassemble everything with no damage, other that an oil pump housing that broke in half getting it out of the bore.

I believe the heating and cooling cycles from the fires loosened up the pistons in their bores.
 
Thanks guys for the tips. I've got all the pistons out.

I ended up removing the crankshaft and then pushing the pistons down the bores with a sledge hammer and 2-1/2" inch drift. A couple of them broke up around the skirt but they weren't usable anyway so that was fine.

One of the pistons bottomed out on the centre main journal. I tapped it back into the bore so the top oil ring lined up with the start of the cylinder bore. With it in this position I hit the skirt on the side with the sledge hammer and it sheared off nicely. I was pretty happy with that.

DSC03532.jpg

Thanks again for your help.
 
I did a post back in 02/04/2012 "How to properly warm up a Flathead". Once you try this you will put your acetone, hole saw and your Big _ Hammer away. It will never fail. It warms up the sludge in the block and you can get your connecting rods out safely. It is safe. If you can cook on a grill, it is no different than lighting starter fluid.
 
Last edited:
You must log in or register to reply here.
Back
Top