Mopar MD127841 Valve, Exhaust

For the setting of the cold clearances after a major overhaul, the actual starting clearance would require the clearing of the half-hot and the normal service checks when the motor is at normal operating temperature. Initial steps involves the of the air cleaner, pulling out the breather hose and unbolting the rocker cover. There are two ways that are used to check and, if necessary, adjust the valve clearances. In the first method, use a ring spanner on the center bolt of the crankshaft pulley to turn the crankshaft until the rocker arm for No 1 cylinder 'just rocks', this means the inlet valve is opening, and the exhaust valve is closing. Position a new set of feeler blades between the face of the No 4 rocker arm screws and the end of the valve stems in such a manner that the feeler blade will only slide in a stiff manner. If not, also unlock the adjuster screw locknut, adjust it until it is right then lock the locknut and do not rotate the adjuster screw. Proceed by rotating the crankshaft and inspects and adjusts the rest of the valves one by one. In the second method, with the assistance of a ring spanner on the crankshaft pulley center bolt, turn the engine until the No 1 piston is at the TDC of the compression stroke more so when both valves of the cylinder are closed. Turn the crankshaft one full turn anticlockwise and if the valves are marked, check the actual clearance on the valve stems. Last, make sure all locknuts are torqued, reinstall the rocker cover and the air cleaner and unset the ring spanner of the crankshaft pulley bolt.

With the cylinder head removed, use a blunt scraper to eliminate all carbon and deposits from the combustion spaces and ports, taking care not to damage the aluminium alloy. Clean the cylinder head with paraffin and ensure that no dirt remains in the ports or bolt holes to prevent gasket leaks upon reassembly. For North American models, clean the jet air passage and EGR gas passage of carbon. After cleaning, test the cylinder head for distortion using a straight edge and feeler gauges; if warping exceeds 0.0039 in (0.1 mm), resurfacing is necessary. Clean the pistons and cylinder bores carefully to avoid introducing carbon into the bores, which could cause damage. Before scraping carbon from the piston crowns, apply grease to the gap between the cylinder walls and the pistons being worked on. After scraping, polish the piston crowns to prevent carbon build-up. Remove the valves by compressing each spring with a valve spring compressor, ensuring not to damage the valve stem. If the retaining cap does not free, gently tap it with a hammer while holding the compressor in place. Remove the valve spring seat and valves, keeping them in sequence unless they are worn. Examine the valve heads for pitting and burning, especially on exhaust valves, and grind the seats and valves if necessary. If severe pitting occurs, recutting the seats and fitting new valves may be required. Clean carbon deposits from the valve head and stem, apply coarse carborundum paste, and grind the valve head to its seat, then repeat with fine paste until a smooth finish is achieved. Clean all traces of grinding compound and test each valve for wear, replacing guides if necessary. Finally, check the free-length of the valve springs and renew them if they are below specifications or have been in use for over 30,000 miles (48,000 km). For jet valves, remove them using a long socket without tilting, dismantle if necessary, and renew the oil seal without further disassembly. When refitting, oil the threads and install a new O-ring seal, tightening to the specified torque.