What is the tdc for a 99 montero sport - Montero Sport Mitsubishi Cars & Trucks

TDC stands for "Top Dead Center". This is where the piston in #1 cylinder is at the very top of it's travel and it has nowhere to go but down. This actually occurs on EVERY revolution of the crankshaft. For engine timing purposes, most repair procedures also expect the valves for #1 cylinder to be completely closed. This happens on every SECOND revolution of the crankshaft. The valves are controlled by the cam shaft. The vehicle manufacturer provides marks on the crankshaft and cam sprockets and on the engine to indicate the crankshaft and camshaft position where this occurs. Please see the picture below.