Get two 6 x 1.0 mm bolts before starting. Position the engine at Top Dead Center (TDC) and remove valve covers, 
Timing Belt, and camshaft sprocket. Take out the four camshafts, starting with the exhaust camshaft sub-gear, then intake and exhaust camshaft. Align cam timing marks on gears. Secure exhaust camshaft sub-gear with a bolt and disassemble camshafts by removing bearing caps. Store caps and valve lifters separately if needed. For exhaust camshaft gear disassembly, mount camshaft in a vise, use a bolt, and remove snap-ring. Reassemble exhaust camshaft gear, lubricate lifters and camshafts, and set exhaust camshaft. Apply RTV sealant to front bearing cap-to-cylinder head surfaces and tighten bolts. Replace camshaft oil seal and lubricate intake camshaft. Reinstall intake camshaft, align timing marks. Insert bearing caps and tighten bolts before removing bolt from exhaust camshaft sub-gear. Reinstall timing belt rear cover, camshaft sprockets, and timing belt. Finally, run engine and check for leaks and functionality.