We have done two of these this year so they must be failing elsewhere also.
Vehicle : Chrysler 300C 3.5L V6 engine fitted from11/2005 on
Problem: Engine still running but with collapsed lifters on one bank.
Cause: The camshaft operates the valves via a twin rocker shaft and alloy rockers for each bank. Lifters are hydraulic. Four valve chambers. The oil feed system comes up through the head and across to the rocker shafts through the rocker shaft posts. The method of holding these rocker shafts from turning is traditional with the exhaust shaft as it uses the rocker pedestal bolts to secure them. However, with the inlet shaft, a hardened roll pin has been used. The fit of this pin in the rocker shaft is very loose and allows radial movement of the rocker shaft within the pedestals and this fatigues the roll pins and each one eventually shears off and drops inside the rocker shaft. The shaft then rotates and blocks off the oil feed to the rocker shafts, rockers and to the hydraulic lifters. Note that the oil feed comes through the hole in the roll pin.
Only one bank will fail. Both banks are modified in the repair.
Cure: We are stripping the assembly down and supplying larger, made to order, alignment dowels that securely hold the rocker shafts from rotating or fretting within the rocker posts. Caution: Take care to reassemble with all oil feed holes aligned correctly through the rocker shafts to each post. Do not get them 180 degrees out. Also take care not to damage or lose the feet off the tips of the lifters.
We are currently looking at a more simple modification for the next one. But the above works for now,.
Hedley James
Ph 03 9372 3111
www.engineaction.com