My 97 Honda civic started ticking in the engine compartment on the freeway yesterday. I was doing about 75-80 mph. I slowed down to about 65 to hear what it was. Then, a few moments after I downshifted out of 5th gear to 4th there was a sound of grinding and twisting metal and then an small explosion with white smoke bursting out of the engine compartment and under the hood. The smoke cleared fairly quickly but I immediately lost acceleration even though the engine was still going. At first, It seemed like the transmission or gears blew up. I pulled over to the shoulder and turned the car off. I could see very, very small amounts of oil dripping off under the engine compartment. The engine never showed that it was overheating. The thermostat read normal the entire time. I let someone else us my car for a while and it may have been returned to me low on oil. I was able to look at the top of the engine and there are no signs of a piston rod shooting through the engine wall. I tried to restart the engine. The starter works but when it tries to engage the flywheel nothing happens, so I'm assuming that something has caused the engine to seize. What do you think the cause of this is? And is there a cheap place online to buy a replacement block used or reconditioned?