I have an engine I plan on using for a new stroker built. My problem is that the pistons are seized to the cylinder walls and I cant spin the crank. So I cant loosen all the rod bolts. Anybody have any ideas how to go about getting the pistons/rods/crank out? Not reusing any of the stock cast parts so I was thinking about just cutting the connecting rods that I cant get to... Any help is appreciated, thanks guys.

Pour penatrating oil in the cylinders & leave it alone for a couple weeks...

After the penetrating oil has worked for a while, a short length of 2"x4" and a heavy hammer works wonders.

Marvel Mystery Oil and Coca-Cola will free those pistons.

If you are not planning on reusing the pistons at all, take a steel bar, punch, chizel, etc and break the crown of the piston from the back side; works like a champ.

I've heard pouring diesel or atf in the cylinders and letting it sit a week works well. Then go at it with the breaker bar on the crank.

Ive been shooting it with PB Blaster twice a day. A friend also suggested brake fluid so I pput that in a few. Marvel oil and coca cola? really works?

I dragged a 400 out of a scrap metal yard for $8, and it was stuck. I laid the PB Blaster to it for a day or 2, then used a piece of 2x4 and a heavy hammer like AHY said. The shock from the whack on top of the old pistons will break it loose. You won't see it turn from the whack, but it breaks the rust bond.Do that to each piston. Then use a breaker bar and socket on the crank, along with more PB Blaster till you get it to spin freely.

Gunpowder work wonders. Some times it's a little hard on the block, nothing a sleve can't fix.

Thanks guys I appreciate it.

I've heard (and not tried yet) that 50/50 mix of ATF and acetone works best.

found this below!!!!!!!!!!!
For all of you that are mechanically inclined and dealing with frozen fasteners:

Penetrating Oils Compared

Machinist's Workshop magazine actually tested penetrants for break
out torque on rusted nuts. Significant results! They arranged a subjective
test of all the popular penetrants with the control being the torque
required to remove the nut from a "scientifically rusted" environment.
Penetrating oil .......... Average load
None ..................... 516 pounds
WD-40 .................... 238 pounds
PB Blaster ............... 214 pounds
Liquid Wrench ............ 127 pounds
Kano Kroil ............... 106 pounds
ATF-Acetone mix............ 53 pounds

The Automatic Transmission fluid (ATF)-Acetone mix was a "home brew" mix of 50 - 50 automatic
transmission fluid and acetone.

Note the "home brew" was better than any commercial product in this
one particular test. A local machinist group mixed up a batch and all now
use it with equally good results. Note also that "Liquid Wrench" is about as

good as "Kroil" for about 20% of the price.

Thanks for posting that, I've got a stuck 340 now and I will try the 50/50 acetone/atf and let you know how it works.