stringfellow
Active Member
Amongs the parts I forgot to order while rebuilding my IO-540-C4B5 was new oil pressure relief valve parts. This is comprised of a steel ball and a spring, and shim washers.
In the Lycoming IO-540 narrow deck IPC, it lists 5 part numbers for the spring (page 1-5.) It's bears an asterisk, for which the footnote says:
"Select spring to give minimum of three threads exposed on adjusting screw to allow field adjustment. Reference SSP-1776 for spring identification"
Ok, so referencing the service table of limits lists the dimension and other specs for the 5 springs. I have the old spring, and I think it's 68668 based solely on the free length (spec says 2.04, I measure 2.06.) It bears no color dye mark.
What really determines which one you need? Without all five at your disposal, how should you choose? Who knows if the core 540 I bought even had the original.
Thanks.
In the Lycoming IO-540 narrow deck IPC, it lists 5 part numbers for the spring (page 1-5.) It's bears an asterisk, for which the footnote says:
"Select spring to give minimum of three threads exposed on adjusting screw to allow field adjustment. Reference SSP-1776 for spring identification"
Ok, so referencing the service table of limits lists the dimension and other specs for the 5 springs. I have the old spring, and I think it's 68668 based solely on the free length (spec says 2.04, I measure 2.06.) It bears no color dye mark.
What really determines which one you need? Without all five at your disposal, how should you choose? Who knows if the core 540 I bought even had the original.
Thanks.