Stock 4.6-liter main caps,...
Stock 4.6-liter main caps, similar to the one on the right, utilize dowel locating pins to speed assembly. Don't confuse these with an extra pair of cap bolts. The Boss main cap on the left is a two-bolt setup that's also cross-bolted like a stock 4.6. It also has machined flats outboard of the main bolts that can easily be drilled should there be a need for four-bolt caps. The folks at Sutton High Performance don't bother with the four-bolt conversion on their EFI Renegade S197.
Aside from its brawn, the Boss 5.0 casting also addresses a slight cooling imbalance evident between the left and right cylinder banks on factory 4.6-liter blocks. Due to coolant routing, a factory modular has better cooling of its driver-side bank than the passenger side. Under extreme conditions, this can impact head-gasket life on the passenger-side bank. The Boss features revised passages that provide a 50/50 coolant split between the banks. Speaking of which, in order to achieve the 3.700-inch bore, the Boss 5.0 is of Siamese-bore design, eliminating the water jackets surrounding the cylinders.
While some might wonder about running Siamese bores on the street, Jesse says, "We've had one of these blocks in Mike Tymensky's street car for more than 30,000 miles, including a trip to Florida and back, so we have a high level of confidence in the block's street application."
FRPP's warehouse has a good supply of Boss 5.0 blocks ready to ship. Cleveland has cast about 1,500 of them, and they're being machined in batches by Roush Industries (see sidebar, The Boss Goes to Finishing School.) If we get a chance to use one for a block-swap tech project, we'll be sure to fill you in on how it does. In the meantime, we give you the details on how this new modular monster earns the honored Boss moniker.
With this clear identification,...
With this clear identification, there is no mistaking a Boss 5.0 block. Yes, it's confusing: FRPP's part number for the block is M-6010-BOSS50, whereas the "6015" on the block indicates a casting or engineering number. This is typical of Ford's numbering protocol.
The Sutton High Performance crew out of Illinois ran a prototype Boss 5.0 iron-block in its e.t. and mph record-setting EFI Renegade S197 during the '07 NMRA season. Previously, they had campaigned both wet- and dry-sleeved 3.700-bore aluminum blocks. Some good reasons for the switch, according to Sutton engine-builder Jerry VanDerLinde, include: "Two different times we actually broke the main webbing out of the aluminum block. No matter which sleeve system we used, they would egg-shape or distort under the power we gave them. We'd then lose compression and power."
But heads-up racers like low weight, right? "The iron-block is 60-70 pounds heavier, but it was more than worth the weight for how much durability we got out of it. The cylinders stayed round all year; the main webbing and the oil pressure were perfect. We've literally had to do no maintenance to the block this year, and we put about 1,240 hp to the crank."
And that's using the two-bolt main caps as issued with the block. Jerry, in fact, opines that this may in fact be stronger than drilling for a four-bolt setup, since that drilling would take structural material from the caps. "The revised cooling system has been a huge improvement to us as well," he says. "There has always been an issue with uneven cooling in the modular motor, and this block addresses that uneven cooling."
Jerry's summation: "If you want to make serious modular-motor power, you absolutely have to use this block."