Rocker Arm Support - Misalignment
89cadillac13Bulletin No. T-90-15
File in Group 6A
Number 109
Corp. Ref. No. 916108
Date Oct. 1989
Figure 1 - Improperly Machined Rocker Arm Support Bar:
Figure 2 - Properly Machined Rocker Arm Support Bar:
SUBJECT: ROCKER ARM SUPPORT MISALIGNMENT
MODELS AFFECTED: 1989 ALLANTES
Some 1989 Allantes may have been built with improperly machined rocker arm support bars. Refer to Figure 1. These vehicles are equipped with a forged steel support, P/N 1641338, rather than the cast aluminum support used on other 4.5L V-8 engines. A properly machined support bar is shown in Figure 2. Note that in the improperly machined bar, shown in Figure 1, the mounting holes for the rocker arm pivot are close to the edge of the bar. This causes the rocker arm pivot to hang over the edge of the support and can lead to cracks developing in the pivot at this point due to the unequal loading. The properly machined support, shown in Figure 2, provides enough machined surface to completely support the rocker pivot. Cracks in the rocker pivots may lead to eventual failure.
During other engine service work the rocker arm support bar should be inspected for this condition. If misalignment is indicated, the support should be replaced as well as all pivots on that side (PN's 1618819 and 1618820).
All parts are currently available from GMSPO.