I have been attempting to unseize the pistons in my 1971 Honda an600. I have tried many methods with no avail, such as wd-40, motor oil and diesel fuel to try to coax the pistons into moving. I have been tapping the top of the exposed pistons with a block a wood and a hammer and no movement. I heard that using phosphoric acid could break up the material between the pistons and the cylinder wall. However I am afraid that the acid could damage the engine. Any thoughts on this?

you might have to heat the block up and cool the piston?

Thank you.

good idea but since this is my first big car project you might need to be a little more specific, I don't know allot about cars but I'm a quick learner. How do you suggest heating/cooling, heating could be done with a blowtorch but how would I cool it?

please correct me if I'm thinking in the wrong direction.

Problem solved.

I used a bigger hammer. 10 pound sledgehammer did the trick.

When all else fails, bring out the hammer. In the future you can try using PB Blaster. That stuff works miracles on rusted/stuck engine parts and nuts and bolts. Soak it and let it sit for a few hours, soak more, try to move it, soak more, repeat until it's free. Worked for me a few engines including a particularly bad 1964 Buick Nailhead motor.

Automatic transmission fluid works well too. High in detergents and works well to get in all of the tight spots. Worked for me a few weeks ago to free up an engine that seized from running out if oil.

brake fluid works very well also. just let it soak for atlleast a day

_________________
1956 oval bug
1958.5 datsun 210
1962 chevy nova 2 400
1965 ford falcon 2door
1965 datsun 320
1966 vw bus sundial camper
1970 toyota corolla ke11
1971 toyota celica st
1972 datsun 510
1972 datsun 240z
1972 toyota corona mk2 wagon
2-1973 mazda rx3