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A pair of poppet valves bent by collision with a piston after timing belt failure. The engine was running at 4500 RPM. In interference engine designs, replacing a timing belt in regular intervals (manufacturers recommend intervals ranging from 60,000 to 104,000 miles) or repairing chain issues as soon as they are discovered is essential, as incorrect timing may result in the pistons and valves ...
The cause is the design of the crankcase ventilation circuit, which Ford revised several times over the engine's lifetime but never completely cured. Due to this, camshaft and tappet wear problems are common. A worn camshaft can cause heavy clattering and ticking from the engine's top end, especially at high engine speeds. [8]
A camshaft operating two valves. A camshaft is a shaft that contains a row of pointed cams in order to convert rotational motion to reciprocating motion.Camshafts are used in piston engines (to operate the intake and exhaust valves), [1] [2] mechanically controlled ignition systems and early electric motor speed controllers.
N-VTC varies valve timing by rotating the affected camshaft relative to the sprocket; valve lift and duration are not altered. This rotation is achieved when an electric solenoid, controlled by the car's ECU, allows pressurized engine oil to flow into and through the cam and into a slave mechanism, axially advancing camshaft timing relative to ...
Properly optimizing the valve duration avoids undue stresses to the camshaft lobes and tappets. 'Valve bounce' is a related condition where the valve does not stay seated because of the combined effects of the valve's inertia and resonance of metallic valve springs that reduce the closing force and allow the valve to re-open partially.
For twin-cam or DOHC engines, VCT was used on either the intake or exhaust camshaft. (Engines that have VCT on both camshafts are now designated as Ti-VCT.↓) The use of variable camshaft timing on the exhaust camshaft is for improved emissions, and vehicles with VCT on the exhaust camshaft do not require exhaust gas recirculation (EGR) as retarding the exhaust cam timing achieves the same ...
The first known automobile engine to use a timing belt was the American 1954 Devin-Panhard racing car, used an engine converted from pushrods to overhead camshafts through the use of a toothed belt made by the Gilmer Company. [18] [19] This car won the Sports Car Club of America (SCCA) National Championship in 1956. [20]
Hydraulic lifters were nearly universal on cars designed in the 1980s, but some newer cars have reverted to bucket-and-shim mechanical lifters. Although these do not run as quietly and are not maintenance-free, they are cheaper. [citation needed] Nearly all modern non-hydraulic lifter arrangements are on overhead cam engines. [citation needed]