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| Chrysler Engine >> CYLINDER HEAD/VALVE TRAIN CHANGES ON 1985-91 ENGINES
Cylinder Head/Valve Train Changes
Chrysler 5.2 & 5.9L (318 & 360 CID) 1985-1991 Engines
Beginning with the 1985 model year, Chrysler manufactured the 5.2L (318 CID) engines with roller lifters & camshaft. The 1989 model year brought the same design to 5.9L (360 CID) engines. Upon doing so, the size of the push rod socket in the lifter increased to a diameter of .650 (16.51mm). Older non-roller heads have a push rod socket diameter of .500 (12.7mm).
Using older, non-roller cylinder heads on the roller lifter engines can result in push rod to cylinder head contact in that area where the push rod passes through the cylinder head. The 5.2L (318 CID) roller cam cylinder heads are easily identified by the kidney shaped or high swirl port combustion chamber.
Identification of the 5.9L (360 CID) head is more difficult, as both heads share the same 70cc combustion chamber.
The roller cam engine also uses a shorter push rod than the non roller engine. The length of it measures 6.794-6.814 (172.567-173.076mm). Non roller engines use a push rod with a length of 7.505-7.525 (190.627-191.135mm).
In the middle of the 1990 model production year, the push rod was changed from solid to hollow. The hollow push rod provides positive oil flow to the rocker arm socket when used with the later style rocker. The later rocker does not have an oil hole in the push rod socket, whereas all earlier rockers had an oil hole opening in the socket.
Be sure to use the appropriate rocker arm and push rod combination when assembling roller camshaft engines. The solid push rod uses a rocker arm with an oil hole in the push rod socket, while the hollow push rod's rocker arm should not have an oil hole opening in the push rod socket. If the hollow push rod
is matched with the rocker that also has an oil hole in the push rod socket, excess oil will be transported up the push rod, through the rocker's oil hole and into the rocker cover cavity. Excessive oil in this area may lead to engine oil consumption if the valve stem seals are overcome.
Along with push rod and rocker changes, the roller lifters were also modified. The lifters that are used with hollow push rods now have an oil feed hole in the push rod socket. Again, use the lifter with the oil hole on engines with hollow push rods.
Extreme caution must be taken when changing cylinder heads and valve train components on Chrysler built 5.2 & 5.9L (318 & 360 CID) engines. Failure to do so, may result in severe engine damage.
For additional information see AERA bulletins: TB 493 & 712
The AERA Technical Committee
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