So I finally got all my block stripped down on my 70 roadster with the exception of #4 piston which doesn’t seem to want to come out and spend Thanksgiving with me. Any tips or suggestion on extraditing said procrastinator? Happy Thanksgiving all!
If you’re hoping to reuse it I’d not want to hammer on it. PB Blaster, time, maybe reconnect the crank and rod, and use a long breaker bar to turn it.
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I guess it depends on how far apart your engine is. When I bought my 3.8 it had been sitting in a barn for 10 years and a couple of cylinders were rusted above the pistons. I soaked the cylinders with various solvents, took the engine out and removed the crankshaft. Then 4 of the pistons could be easily removed from the bottom. For the other two I took a piece of a 2x4 (wooden stud) and shaped the end to the shape of a piston top and the edges to fit inside the cylinder. Then I put it on top of the piston and wailed on it with a 6 pound sledge hammer. Since the cylinder rust was mostly above the pistons they came loose without too much difficulty. When I cleaned up the pistons I was surprised to see that there was no damage to them. I replaced the rings, honed the cylinders and put the pistons back in. That was in 1985 and I’m still driving it.
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I’ve just (this week) done exactly what Mike has described with great success on 2 pistons. However it does depend on where about the pistons are stuck, if they are on the bottom of their stroke the room to push them down is a bit limited. Using the crank with a lever is not an option I can see working, another option is to use a hydraulic press which is not that difficult to do using a bench top type press.
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Wish I had access to a press!
I once had a piston very stuck and had to take the block to a machine shop where they drilled holes in the piston until weakened enough to be pressed out.
Dennis
It’s been soaking for months from the top now soaking from the bottom with pb blaster. I will probably do what Mike did and try to force it out the bottom as is almost all the way down but thinking first I will try pounding both ways with some hardwood. Just need to find a source for hard wood. Wish I had kept some of those old pallets!!!
Thinking far outside the box. Would it help if you were to place a large piece of dry ice on the piston and let it cold soak, and hopefully shrink, before you tried moving it?
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Hey I read something about that … could be worth a try!!
Some good stuff there.
Nothing to add to that!
Turned into a bit of a hobby 
The little Thor barely got them out, of course there’s a bigger one for difficult cases. Soak the pistons, hammer away. It’s not the rings as much as crud clamping the pistons in the bore.
I have a rebuilt by the Jag dealer MKVII motor that has been seized for a long time
The pistons and all other parts look brand new
As a first course of action, I was thinking to hammer upwards on the flats of the conrod with a block of wood and deadblow hammer
Not savagely, but patiently
Is there any reason I should not do this ?
I have removed stuck pistons before, and while I may try and knock them down a bit at first, they eventually come out the top
The bores have been soaking in turps/ATF mix for at least 3 months
I have had mixed success getting Jag pistons out in the past
The rings can be jammed in the piston lands, or rusted to the cylinder wall
Yes, they deform a bit. It’s how I got mine out. Try bashing them down and clean out + oil the bore before hammering them up. Make a hardwood piece that fits the conrod big end and hammer on that to get it out. I think that’s the best way.
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More thumping to come !
John…have you tried some hear from underneath around the outside of the bore just to expand it…Steve
There are a gazillion videos on YouTube, like this, and I think I’d like to try this on the Jag engine. I have just to see if it would work!
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I once had a stuck piston in a Land Rover block that could not be moved with any amount of penetrating oil, heating with a MAP gas torch, or knocking.
I took it to my friend’s machine shop, and he sort of said “Here, let me show you how it’s done”….then he proceeded to spend about the next 90 mins heating the bore with an oxy-acetylene torch, bashing, and swearing.
The piston came out in about 6 or 7 pieces…it was well any truly seized in the bore, around the full circumference.
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