You have to think an O-ring receiver groove is the first machining step when running 52 pounds of boost. It's followed by full chamber polishing, plus the porting, guide, and seat work. The seats and guides are the usual silicone bronze parts, but they are carefully installed using nitrogen chilling and diamond honing of the guides, which are held to 0.0001-inch accuracy.
Accufab does its own porting, starting with a CNC program and finishing by hand. The intake ports are not radically changed. The floor of the port is simply cleaned, while the roof and bowl are opened around the backside of the bowl. This makes more of an oval shape relatively deep in the intake port to keep the cross-sectional area the same throughout the port.
The exhaust ports are more rationalized than anything else, with a slight D-shape visible in the runner. Looking at this already-run head, it shows that port matching is clearly no big deal on the exhaust. It's also interesting how the square intake port's guide has been trimmed or set flush with the runner roof, but the oval port shows some guide to the intake wind.
At 52 pounds of boost, the head gaskets squeeze out no matter what, spraying water outward and downward--perfect for lubricating the rear slicks at 200 mph. As the catch pan under the engine can't capture this pressurized water, and even John can't drive on watered slicks at a football field-per-second speed, something had to done. For a while they thought trick gaskets, more torque, and dowel pins were the solution, but the gaskets still forcibly leaked.
The fix was to eliminate the water entirely at the block/head interface by blocking all coolant holes and routing the water externally using hoses at the rear of the block and heads. Here the blocking process is captured in mid-job, the passage at left having already been CNC'd to shape, and the passage to the right has its CNC'd plug nitrogen-chilled and installed. When all the plugs are in, the head is milled flat again. The same process is employed on the block deck, too, so even if the head gaskets give some--and they always do at 2,300 hp--they won't leak water.
In the beginning, John bought and ran other tuner's gear, but as he searched for more power, he's moved more and more to his own parts. The intake valve is one example: Considerable power was found by narrowing the lower stem and altering the transition to the head, so now Manley makes these valves for John. Interestingly no power was gained by fiddling with the exhaust valves.
Custom camming is obviously part of John's program. Comp Cams does the grinding, with the intakes measuring 256 at 0.050-inch lift and a total of 0.495 valve lift. It doesn't sound like much, but with all that boost pushing and a Four-Valve head, it doesn't take radical valve grinds to move literally tons of air. Fred says the cams feature easy ramps to keep the rocker arms alive. Like the stockers, there aren't any keyways retaining the cam sprockets to the cam, just 160 lb-ft of torque on Accufab-specific ARP retention bolts.
What's trick about the cams are their undercut lobes. This is done to dynamically balance the camshafts, as John tore the car apart to find a vibration at 6.500 rpm and higher. The parts-breaking buzz turned out to be the cams, which are now balanced in-house at Accufab by John. The actual cutting is done on old manual mills and is a real pain, according to John, but the results are worth it as the engine is now Lincoln-smooth and more powerful. We've never seen balanced cams before, but with four weighty shafts; large, heavy lobes; and high rpm, it's clear the cams could act like imbalance shafts.
Two Hogan Racing Manifolds have been used on the Accufab 4.6-liter recently. The first was named Anna Nicole, but it has since been replaced by this as-yet-unnamed second-generation intake, which flows an additional 20 cfm. Note that two injectors per runner are used, and the fuel is ingested from both ends of the fuel rail and balances in the middle. The injectors are placed as close to the combustion chamber as possible.
Ford has used large (common) and small (Cobra R, Ford GT, and GT500) lash adjusters. The older "B" head John uses employs the large lash adjusters, which he often grinds shorter on the bottom to put the lash adjustment where he wants it. The valvetrain is adjusted by way of valve-stem height, with each valve requiring individual adjustment, otherwise cylinder-to-cylinder breathing variations occur, says Fred, and getting the lash adjusters spot-on is part of the process. They've found these adjusters super sensitive to clearances, oil weights, and oil additive packages.