In the midst of building up my 3.4 dohc. I have the five pistons in the block allready good to go, but my last piston has the old compression rings pretty seized onto it, we have left it dunked in carb cleaner for 2 days but we still don't know how to go about getting them off of the piston.

if you dont need to re-use them, just pry them out.

try soaking it in acetone. then work it lightly by hand to get it in, it should break up the carbon. a light tap with some wood may also help. I;ve found acetone works better for breaking up carbon.
another good thing that is very thin and penetrates is starting ether.
if you can see the split, you might be able to work a utility knife tip in ther carefully to start spreading the ring, that works too, but be careful, don;t scratch the piston or put the knife thru your hand....

DO NOT SOAK IT IN CARB CLEANER EVER. I have for years and have seen twice it ruin the pistons. The first time it froze the pins. The second time the rings had been some what free and they were saoked to free them up and the seized to the pistons. I have for the last few years used GM Piston and Ring cleaner.
Piston and Ring Cleaner, P/N 12378549 (in Canada, P/N 88901334)
I also used GM's Top engine Cleaner P/N 1050002 Top Engine Cleaner (U.S.) 992872 P/N Top Engine Cleaner (Canada)
In the last year GM has issued some information on how Top Engine cleaner DAMAGES METAL PARTS. I have noticed some reactions on some parts. Like the piston pin bushings turning green and black. The pistons turn dark grey.

GM has a new Cleaner that does not damage parts. I have used it on a set of piston that had been in a engine that had set out side with the plugs out. It cleaned the pistons and the look great. The rings came out with no problems after the soak.

GM Upper Engine and Fuel Injector Cleaner 473 ml (16 oz) Container (U.S.) P/N 88861802
GM Upper Engine and Fuel Injector Cleaner 473 ml Container (Canada) P/N 88861804

I had a piston that I was using for a mock up and I cleaned it up even after it had been in Top Engine Cleaner.

------------------
Cadillac Tech
ASE MASTER TECH since 1988

86 Northstar Fiero
85 RX7 former SCCA car
56 TR3 small mouth 6.0L
A.J. Whiteley