The first engine for the P-51 was the dependable and very underpowered Allison V-12 1250 hp. V-1710.
[img]http://www.aviation-history.com/engines/v1710-4.jpg[/img]
[url]http://www.unlimitedexcitement.com/Miss%20US/Allison%20V1710%20Engine.htm[/url]
The Brits then took 4 of the Allison powered P-51's and re-engined them with the more powerful Rolls-Royce Merlin engine.
[img]http://www.wpafb.af.mil/museum/engines/eng33.jpg[/img]
The US AAF was impressed with the performance gains and a deal was struck with Packard to manufacture a liscensed copy of the Rolls-Royce Merlin. It was known as the Packard V-1650-7.
It produced 1600 hp and is what made the P-51 the aircraft it is.
The same engine also powered two of Britons best fighters of WWII, the Hurricane and the Spitfire.
[url]http://www.spitfiresociety.demon.co.uk/engines.htm[/url]
If you are really wanting that Allison or Rolls-Royce / Packard Merlin engine you might give these guys a call:
[url]http://www.mysteryaire.com/[/url]
They have a Crankcase and bearings for a Merlin for sale at $25,000.
[img]http://www.mysteryaire.com/images/v12right.jpg[/img]
You might also try the Hydro guys.
On a personal note, where I grew up our next door neighbor used to race the Hydro circuit in the late 50's and early 60's.
He stopped racing in the late 60's, in his garage he kept a complete Rolls-Royce Packard Merlin 100, brand new in the crate, never touched. He died in 1987 and his wife died the next year. My dad was the caretaker of his property untill their next of kin could come by and liquidate the property. My dad was shocked when one of their relatives sold everything in the garage for $15,000. I am talking a complete machine shop, welding shop, tools, a Model-T Ford, that Merlin engine, gone for $15,000.
If you want to build your very own scaled down P-51, here is the web site for you:
[url]http://www.precisionaeroeng.com/[/url]
and:
[url]http://www.kitairplaneforum.com/gal/nhstewart/index.html[/url]
Some general info:
It features two seats, dual controls, all aluminum construction and is powered by a V-8 engine.
There are approximately 50-60 active builders of the S-51D and 13 aircraft are already flying. You can expect to pay around $215,000 for a kit which includes propeller, reduction gear, engine, accessories drive case and all accessories.
The S-51D will be powered by a Sabre V8 engine which is an aluminum block derivative of Donovan Engineering's big block Chevy racing motor.
Sounds like fun!