In fact, when the F-82 was ordered, the prototypes had Merlins in them. The first prototype flew 26 June 1945. Since the war was ending, Rolls Royce was bumping up the license fee for the Merlin and the US Army Air Corps asked Allison to design a new, higher powered V-1710 for the plane. They undertook to do this and the Allison G series resulted. However, in the Air Corps, the powers that be were MUCH more interested in jets, and cut the anticipated and dangled order for 1,000+ P-82's to under 300 aircraft. In the end they delivered 270 aircraft and the P-82 was the last propeller-driven fighter ordered in "quantity" for the Air Corps / USAF. The Army Air Corps got EXACTLY the spares they ordered.
Allison did not produce engines without orders from a customer and most businesses won't either when the product costs as much as a V-12 engine costs. The powers in the Air Corps / soon-to-be-USAF were not really interested in the P-82 / F-82 and didn't order normal or even close-to-normal spares or even bother to keep up with suggested maintenance, even going so far as to fly the G-series engines well beyond recommended overhaul. Many of the P-82's were grounded for lack of spares that weren't even engine related. Some parts are typically "consumable," but engines usually aren't. Things like seals, O-rings, filters, etc. require changing at regular intervals, much like a car.
The Allison G-series engines we build run just fine and, when operated by the book, give good service. But the Air Corps didn't even keep up with new pilot training. Many P-82/F-82's were flown by people given only a brief "cockpit checkout." I flew radio control for a LONG TIME and one of the people I flew and talked with in Phoenix, Arizona an several events was Col. Robert E. Thacker who holds several P-82 records including one from Hawaii to New York. He said that the P-82 was a bit of a "Stepchild" and was sometimes flown by people with little training in it. It was a propeller fighter in a time of transition to jets and was not exactly lavished with care. Basically, they wanted the props to "go away" and every red-blooded fighter jock wanted to be assigned to jets.
When the spares dry up, the planes sit out in the weather (since the jets were in the hangars) and don't exactly get better or even stay the same. They deteriorate unless they are active, like any machine.
It is incorrect that the Allison G-series engines were the major reason for the P-82's main headaches. They experienced issues because the service didn't want them, didn't order even half the normal spares, didn't do much of the regularly-scheduled maintenance, didn't even pursue piston pilot training past the first couple of classes, and didn't pursue piston mechanic training either since they were being retrained on jets. As fighter piston mechaincs left the service, they were not replaced. They certainly didn't do the normal carburetor overhauls every 2 – 3 years these days, but scheduled every year when in service.
Our Allison V-1710 G-series engines run just great, and I firmly believe the new ones at the time did too, especially since our G-engines are the SAME ones that were produced and used at the time. Sorry, I don't buy the old, tired Allison-bashing based on personal experience with the Allison. They run just fine for years. At least ours do.
Not trying to start anything, but also not going to hear the some old Allison-bashing without a reply. We currently have an order backlong of 20 engines and more than 60 in service in flying aircraft. We have Allisons out there running fine after 12 - 15 years in the plane! Does that sound like an unreliable engine? Our biggest issue with our run-stand left-turn engine for the past 6 years has been keeping the battery charged, not the engine (we don't run an alternator since it is just a display engine). Otherwise, it starts and runs every time, and we use it to train new Allison owners how to start and run their newly-overhauled Allison.