After a career in Ford engine...
After a career in Ford engine development, Modular Performance's John Tymensky has forgotten more about modular engines than many engine builders will ever know. Here he demonstrates the gentle, one-thumb-push he insists is correct for installing modular pistons. Any extra force is too much.
Horse Sense: If big-bore modulars are your desire, the Boss 5.0 block is your best bet. An aluminum big-bore block is unlikely, as the configuration is bulky and there's minimal room for liners.
With a name like Modular Performance, you expect modular V-8 expertise, and you get it. Not only is the father-and-son team of John and Mike Tymensky well-versed in the art of building drag engines, but John is a recently retired Ford engine engineer with tight factory ties. While on active Ford duty, he developed the modular engine at his day job and hot-rodded it at night. John remains one of the most accessible experts on the engineering, manufacturing, and hot-rodding of Ford's modern V-8; it's his family business, after all.
Always dealing with the latest products, Modular Performance is now building engines using the recently arrived Boss 5.0 block from Ford Racing Performance Parts. We detailed this wonder block in our Mar. '08 issue ("Block Party," p. 64), but in case you missed it, the iron Boss 5.0 is the strong block for modular builders going big on power as well as displacement.
Pivotal characteristics of the Boss 5.0 block include a 4.6 deck height, so it fits anywhere a stock 4.6 block does; a 3.700-inch bore for a nominal 5.0-liter displacement; cast-iron material for bridge-abutment strength; reinforced bulkheads and other important architecture; siamesed bores for improved cylinder-wall stabilization; and about a $2,000 street price. In short, the Boss 5.0 block is the last word in modular V-8 strength. It's beneficial starting at 500 hp, and definitely the way to go with big-power turbo, blower, and nitrous cars.
For this story, John ran us through a build using the Boss 5.0 block and a Kellogg custom crankshaft. Kellogg makes Ford's modular crankshafts, so this 3.750-inch stroker shaft shares that comforting OEM look and feel. The resulting displacement is 5.3 liters, a handy thing when the engine packages and looks just like any other 4.6 Mustang mill.
Diamond forgings with a quiet-running...
Diamond forgings with a quiet-running 0.050-inch pin offset are John's choice. The pin offset reduces "flop over" at top dead center, allowing a better ring seal with modern, narrow rings. John specifies a little more barrel to piston skirts going into forced-induction engines such as this one for the same reason. The pin is 22mm in diameter with 0.155-inch-thick H13 material-hard stuff. Because of the nitrous, the piston dome is also thicker at 0.250-inch.
Our subject engine is destined for street/strip duty, with a 200-horse nitrous hit plumbed into its EFI circuitry. The Four-Valve '03-'04 Cobra cylinder heads were supplied already ported and assembled by the owner. The idea was to keep the engine relatively simple and the rpm between 7,200-7,300 because the stroker configuration generates considerable friction. Still, the powerband plateaus at the peak-a Tymensky trademark-so the engine can be routinely driven out the back door at 7,700 rpm while only nosing over 3 hp.
Roughly speaking, the assembly in the photos follows Modular Performance's FRPP Big-Bore Stroker Kit specifications. The Big-Bore Stroker, using Manley rods, lists for $5,757 at Modular Performance. Add $650 for Oliver billet rods for all-out, pure-race short-blocks.
In the photos, we're concentrating on a few highlights of how Modular Performance assembles its engines rather than trying to show every step. It's instructive to see the emphasis John and Mike put on torquing the fasteners, along with the care exercised around the piston rings. As always with the best engine builders, nothing goes unchecked. There are no secrets-only accuracy.
Those charmed by happy endings will enjoy hearing the engine made 490 hp and 375 lb-ft of torque on pump gas with the owner's own tune. Call it 700 hp on the squeeze with a long, happy life in front of it thanks to the heavy-duty block.
Not To Bore You, But...
Small cylinder bores are a modular engine's weakness. The small bore shrouds the intake valve, which reduces breathing. It also promotes poor in-cylinder mixture distribution at times, leading to hot spots.
The higher the valve lift and sharper the tune, the worse the small bore phenomena. FRPP's big-bore block helps with these problems, which is one reason an engine built with the new block should outperform the same displacement engine built using a stock block with more stroke.
Manley 4340 H-beam rods are more than strong enough for the moderate-rpm, moderate-weight pistons found in typical performance modulars. Chevy specs rule the rod world; these measure 5.850 inches center to center, swing on 2.00-inch journals, and clamp with 3/8-inch ARP bolts. Flat-top pistons ensure good flame fronts and reduce the chance of knock while still providing 10.8:1 compression. The intake eyebrow is the only relief on the dome, the result of John's "interesting" software that indicates the piston-to-valve positioning for each degree of crank rotation.