Rolls Royce Merlin vs Rolls Royce Packard

[Jag34]

Here is a question I have wanted answered for some time. What is the difference between the Rolls Royce Merlin and the Rolls Royce Packard? I know there were built in the U.S. during the war (under contract). Was there a big difference in them? Could the parts from a British Merlin be placed on a Packard Merlin?

I wait for your answers.
 

[GScholz]

The motors were more or less identical, but with different reduction gearing to better suit the American planes they were to power.

Merlin 28 ~ Packard V-1650-1   P-40
Merlin 63 ~ Packard V-1650-3   P-51B
Merlin 66 ~ Packard V-1650-7   P-51D
Merlin 100 ~ Packard V-1650-9   P-51H

[Greebo]

The differences between RR and Packard-built Merlins were things like having different engagement splines for the propeller and different carburettors. Not too important in terms of performance but the sort of thing mechanics need to know.

Packard built two main types of Merlin engine. The first was a version of the Merlin 20 series which had a two-speed single-stage supercharger. These were mostly used on British aircraft like the early Mosquitoes and the Lancaster. The only US aircraft I can think of that used it was the P-40F. Later Packard built variants of the Merlin 60 series which had a two-speed two-stage supercharger. This gave much better altitude performance and was used on the P-51 as well as some Mosquitoes and Spitfires.

[SirNuke]

there is an engine out there that was both built in metric and imperial units iirc...

[GScholz]

Who used the metric units Merlin?

[Chalenge]

No one uses 'metric.' Both Packard and Rolls-Royce use the Imperial system.

You know, Ford in Manchester, England helped in war production of Merlins at the same time that Packard built them in America. Both Ford and Packard were held to Rolls to change nothing in the design. So, even before they could begin making the hand-built engine (soon to be mass-produced in America) they had to redraw all of the plans to suit their own manufacturing standards. As the Merlin was updated in the Rolls factory those details needed to be updated in the new plans. It took nearly a year for everything to reach completion. Packard created their own Imperial fasteners, because in America there simply were none.

Ford and Packard both requested that tolerances be reduced, because the Merlin was incredibly loose by their racing standards. They were denied because every component needed to be interchangeable with any standard Rolls Merlin.

Packard did share material changes with Rolls that allowed the bearings (using Indium) in the engine to last longer which increased service life. When the Germans discovered the Indium in captured aircraft they assumed it was an impurity from inferior American designs.

If you had a Packard built Merlin in the 1960s your parts were still covered by Rolls under their warranty and their claim that their parts 'do not fail.' Something to note in today's world.