With the powertrain back where it belongs, a cold-air induction system is added. Notice the relocated alternator on a Roush-cast bracket. Almost all that's left to do at this point is to reflash the processor with the P-51A-specific calibration. We've skipped about a million steps, but now you have an idea of what it takes to essentially assemble the highest-powered Roush special edition to date. After observing the whole process, we'd love to tuck a P-51A in our hangar.
Performance Assembly Solutions
Though located within the same Plymouth Road Technical Center, engine teardown and assembly for the P-51A is the responsibility of Performance Assembly Solutions, a joint-venture established by Roush Industries as an assembly supplier of niche and specialty powertrain modules. Yet another example of Roush business diversity, PAS is in the business of building engines for a variety of corporate clients, some of which might surprise you. For the P-51A, the same engine that comes out of any factory GT goes back in, only with a much stouter bottom end and a Twin Vortices Series Roushcharger on top.
Disassembly comes first, with the new GT Three-Valve modulars stripped down to their bare blocks. Their pistons, rods, six-bolt cranks, and crank dampers become orphans. | 
Forged Mahle pistons-made to Roush specs with a 16cc dish for about 8.6:1 compression-replace the factory 9.8:1 hypereutectic slugs. Phosphate-coated and with Mahle's Grafal skirt coatings, these are of standard-bore diameter; there's no need to bore or even hone the factory-fresh aluminum blocks. | 
The P-51A's steel H-beam rods, sourced from Manley, are basically clones of those used on the '03-'04 Terminator Cobra, and we know how tough those are. ARP 8740 rod bolts are used, along with Speed-Pro main bearings. |
Likewise, the forged-steel Kellogg cranks are the same eight-bolt units as were installed in the Terminators. There's no sense reinventing the wheel-when you have a crank as proven as this one, use it. | 
Once the long-block is fastidiously reassembled, the icing goes on in the form of a 2.3-liter Eaton TVS Roushcharger. It sits atop a Roush-cast lower intake, which houses the air-to-water 'cooler elements. The setup also gets an application-specific fuel rail and 52-lb/hr injectors, and it breathes through a GT 500's dual-60mm throttle body. | 
The P-51A's new eight-bolt aluminum flywheel is an SFI-approved McLeod piece. An upgraded clutch disc is also part of the deal, though the stock pressure plate remains. |
For use under boost, plugs are gapped down from 0.041 to 0.032 inch. By the way, a welcome running change (that occurred sometime around January) in factory Three-Valve engines is the swap from the hard-to-gap and hard-to-find 14mm closed-electrode plugs (top) to a 12mm plug with a more traditional electrode arrangement. | 
Every P-51A engine assembly is cold-tested to check for leaks and correct oil pressure. Each cylinder is also compression tested. | |