i just bought a 67 gto with the original 400 motor, but the sparkplugs were out of it, the owner said that they had been out only 6 weeks, but i am guessing longer, because the pistons are stuck in the cylinders by rust. i gently tried to see if i could break it loose, but it didn't budge, so sprayed some wd40 into the sparkplug hole and am letting it sit . i have heard of many things to spray or pour in the motor to bust the pistons loose. but thought i would ask here, i really don't want to tear the motor apart if i can help it. so what can i pour or spray into the sparkplug hole to free the pistons up.???or only other things i can do?