Papitto: The pros of modular engines are that they're a modern design and, up to a point, are actually less expensive to build than a pushrod 5.0. It's no secret that the stock 5.0 blocks and cranks fall apart just past 500 hp. The modular engines can be pushed far beyond 500 hp using a production block, crank, and heads. Some examples are the supercharged Two-Valve pump-gas engine that makes 700 hp and the supercharged Three-Valves that make more than 800 hp with a cast stock crankshaft. The Three-Valve engine did fail after a year-it broke the nose off the stock cast crank due to the extreme loads put on the front of the crankshaft by the drivebelt spinning an F1R ProCharger. Another example of a Four-Valve is a turbo-charged 5.4 Navigator-based engine that put out more than 1,000 hp. All of these examples used stock Ford blocks, cranks, and cylinder-head castings. An extreme example is a twin-turbo 5.4 Ford GT that is street driven and puts out more than 1,400 hp.
The overhead-cam design allows for a light and strong valvetrain. My own 5.4 has been running for two years at speeds over 8,800 rpm without any sort of valvetrain problem. The Four-Valve cylinder heads have great airflow potential to go along with the tough valvetrain. To get anywhere near these numbers with a 5.0 would just about require the engine to be totally built with aftermarket parts.
The cons are at some point the production parts are not strong enough to make really big power numbers, and there are almost no aftermarket blocks, cranks and heads for the modular engines. Also, the modular engine series is displacement limited by its small bore centers.
MM&FF: How did you come to specialize in modular engines?
Papitto: After 20 years of drag racing motorcycles, including four years of Pro Stock Bike, I had a lot of experience with overhead cam, multivalve engines. When I stopped racing Pro Stock bikes, I started playing around with my '97 Cobra that I owned for about a year. The first modular engine that I built was a 5.4 Navigator-based engine-it produced over 420 hp on UPR's dyno. I had fun building that engine; the big Four-Valve heads had a strong resemblance to the Four-Valve Suzuki engines that I had raced for years. After that, the phone started ringing-people were interested in Four-Valve engines. I took the car to Dave King's Modular Shootout in Maryland, and it won the Four-Valve naturally aspirated class. I beat on that Navigator engine for over a year, and a failed oil pump eventually killed it.
MM&FF: What are the most common misconceptions that people have regarding modular engines?
Papitto: That the engines are weak and too complex.
MM&FF: What are the weakest parts of the 4.6 and 5.4 engines, and at what power level do they become an issue?
Papitto: The stock connecting rods, pistons and, in some cases, the stock oil pump. [Regard-ing the second part of your question], I would say around 450 hp. There are some cases where I've seen stock early Cobras make over 550 with no problems. The '03 and '04 Cobras, by virtue of having Manley H-beam rods and forged pistons, do quite well at 550 hp or so. Much beyond that level, the main caps on the two-bolt main iron block begin to move around enough to transfer metal from the caps to the block.
MM&FF: Boring and stroking the modular motor-is one better than the other? Why?
All of the GT blocks are hand...
All of the GT blocks are hand signed by the builder at Ford.
Where the stock GT rods are...
Where the stock GT rods are an H-beam design, Boss 330 uses Manley's forged Pro Light I-beam design. "They're basically the same in strength," Papitto says, "however, our connecting rod uses ARP 71/416-inch rod bolts instead of the smaller, stock 31/48-inch 8740 fasteners." Also shown is the Boss 330/Mod Max piston, the stock Ford GT piston from Mahle, along with the stock wristpin, and the Boss 330 180-wall, tool steel wristpin.
There are a couple of things...
There are a couple of things to note in this picture. The first is the corroded, stock Ford GT rod on the right. Papitto told us that what you see on the connecting rod is just a small sample of the corrosion that had occurred in the engine due to the extended use of high-octane, leaded race fuel. Frequent oil changes can somewhat quell this situation and should be mandatory when using that type of fuel. The spindly connecting rod and piston on the left is a stock Shelby GT500 unit. Papitto says that while the rod is plenty strong, they still use the cracked cap design, which isn't the best in a high-performance application.
Here, you can see how Boss...
Here, you can see how Boss 330 moves the top piston ring down to avoid the intense heat in the combustion chamber. This is a modification particular to the boosted modular engine. Normally aspirated engines actually work better with a higher ring location. For this buildup, religious use of 116-octane fuel allows Boss 330 to equip the pistons with a smaller dish to elevate compression to 9.0, from the stock 8.4:1.
Part of the 5.5 buildup includes...
Part of the 5.5 buildup includes new valvesprings and valves. The stock spring is a single-spring design that offers 65 pounds of seat pressure closed. The Boss 330 spring is a double design that bumps up seat pressure to 95 pounds.
If you hang around long enough...
If you hang around long enough at the Boss 330 digs like we did, you're likely to find some interesting modular components laying around. This is Papitto's first crack at a 5.4/Four-Valve intake manifold. The lid is a prototype piece, while the runners are four pairs of the Lincoln Navigator's stock rear runners.