B767-300 air carrier powerplant line engineer reported finding the wrong hardware installed on a B767 engine mount.

Narrative

I am a senior powerplant line engineer and during my on-call shift; I received a call to assist Line Maintenance with a discrepancy with the findings of the engine mount bolt threads as installed. Maintenance reported that they had installed bolt BACB30PN14-25 in lieu of bolt BACB30PN14-30M which were called out in Task card XX-XXXX-X-XXXX step XX. I reviewed the task card step XX (which was already signed off); the AMM (Aircraft Maintenance Manual); and AIPC (Aircraft Illustrated Parts Catalog). Bolt P/N BACB30PN14-30M or -30 is not present in the AIPC and BACB30PN14-25 which was listed in IPC section 71-21-01-03 Item 15. I researched further and found AMM section 71-00-02-420-802 which lists the different engine mount configurations that can be installed and directly states that the BACB30PN14-30 bolts are to be installed on main mount assembly 310T4020-16; -24; -3 or as identified as P/N 310T4020-600U2 (Recoverable Assembly Kit). With the Aircraft in ZZZ; I walked down to the aircraft and notified on sight maintenance to determine the P/N of the installed engine mount assembly. A Technician was able to read the P/N of the engine mount as the P/N 310T4020-600U2. I directed them to AMM section 71-00-02-420-802 Table 1 (Mount Identification) while at the aircraft and directed them to remove the installed bolts (P/N BACB30PN14-25) and install bolt P/N BACB30PN14-30. I left the area following their agreement and came back later to see QC and the technicians in the process of installing new bolts. The Engine Mount Bolts are one of the most important parts for securing the engine to the aircraft Pylon; if this was not caught; it could lead to inflight failure of the aft mount bolts and the engine coming off wing. This could easily cause loss of aircraft control and catastrophic loss of life. I cannot stress the importance enough of the serious potential risk to life if this was not caught. Please review and personally let me know what comes of this as it is personally unsettling.