Incidentally flight engineers always reckoned that the RR Merlin engines built under licence by Packard had longer working lives than RR produced Merlins.
My late father who was in the RAF always said that the Packard Merlin was superior in terms of ignition system,carburettor & supercharger he worked on them in N.Africa so there was a difference in operating conditions to Britain,BTW the P51(Mustang) only became a good aircraft when the Merlin was fitted