Before final assembly, all...
Before final assembly, all D.S.S. Racing short-blocks are balanced on a Hines Eliminator computerized spin balancer. The crankshaft is spun at 500 rpm with adjustable bob weights. The bob weights are then made to be the same weight as the specific pistons, rods, rings, and rod bearings for each rotating assembly. The computer senses the heavy and light part of the crankshaft and tells you where to drill or add material to make it balanced. Not only does it tell you in degrees where to remove, but also how deep to drill. There is no guesswork. A final check spin indicates you are balanced to spec and ready to go.
Last Month, we gave you an intimate look at the new Boss 302 engine block from Ford Racing Performance Parts ("Major Management Muscle"), and briefly talked about our plans for the rotating assembly that would eventually propel our proud project car, Stolen Goods. This month, the D.S.S. staff screws together our Super Boss Bullet, and we'll show you exactly what's going in our big-bore 347ci powerplant.
Having set a goal of 400-425 flywheel horsepower, and choosing to go with a 3.250-inch stroke, a 5.315-inch connecting rod, and a 4.125-inch piston, our Boss 347 presented a couple of challenges when it came time to assemble it. While FRPP has 100 or so of these blocks out in the hands of various engine builders, ours was the first that D.S.S. Racing had seen come through its doors, so the machining process would be slow and precise. The big-bore combination has been done before, but since the hunk of iron is an all-new casting with its own characteristics and traits, it would require an entirely new CNC milling program.
Machining the cylinder bores and crankshaft centerline is fairly easy, as the mathematics involved are mostly the same for all engines. However, machining the lifter bores was a task that Tom Naegele at D.S.S. Racing was a bit tentative to complete.
The Boss 302's new casting features big, beefy lifter bores that allow you to run extra-large lifters or offset lifters. Offset lifters allow more radical port designs so you can straighten the ports and drastically increase port volume without a pushrod tube intruding into the port. Larger-diameter lifters are common in circle track, flat-tappet cam designs, as they allow for more radical flat-tappet cam profiles.
As our engine will be using a hydraulic roller camshaft setup, we needed to make sure the lifter retaining cage would apply the proper amount of pressure to the lifters. After mocking up the cage and lifters, Naegele wasn't happy with the tension that he was seeing, so the lifter bosses needed to be machined down for a better fit.
The three-step honing process...
The three-step honing process that D.S.S. uses on all its Level 10 and 20 blocks took years to develop and perfect, and is performed using a Sunnen CV616.
In order to retain the factory...
In order to retain the factory retaining hardware, the Boss block needed to have almost 11/44 inch machined out of the lifter bosses. Ford Racing Performance Parts put plenty of meat in this area so people could modify them for bigger and/or offset lifters.
Here are the machined lifter...
Here are the machined lifter bosses on our Boss 302 block. The machining is standard in D.S.S.' Level 20B race prep. Level 20B is a special CNC program just for Boss blocks, and since the Boss already has screw-in freeze plugs, D.S.S. put its machine time into the lifter bosses instead.
"Usually we obtain a junk block to fine-tune our CNC program on, so I was a little concerned about using this production piece," Naegele says. Though our block was a production piece, they were a bit hard to come by at the time we wrote this, and with deadlines hanging in the balance, we couldn't afford to mess it up. Naegele and the D.S.S. crew handled the job superbly, though-no doubt a result of their vast experience in building engines of all sorts. Keep in mind that this process is not necessary for link bar-style lifters or flat-tappet lifters, just the OEM hydraulic-roller hardware.
One of the other procedures that D.S.S. performs to all of its blocks is torque-plate honing. Head-bolt torque can distort the cylinder bore, hindering ring seal in the process. Proper use of torque plates prestresses the cylinders so that when the head is torqued on, the cylinders will be exceptionally straight and round. "The D.S.S. Level 10 and 20, which feature this process, have been dyno-proven numerous times to be worth 30-40 hp over commonly used performance rebuilding practices," Naegele says. "Attention to detail, not how fast you can get it done, is the key to power and longevity."
The piston-ring package on a small-block Ford stroker engine is extremely important, not only for making power, but for engine longevity as well. On our build, D.S.S. used Speed-Pro severe-duty ductile iron, plasma-moly rings. The rings' end gaps are adjusted to match the intended application, with wider gaps for boosted or nitrous-fed applications and a tighter gap on naturally aspirated combinations. Piston-ring design and choice is directly dependent on piston design, and these again are important to the architecture of a small-block Ford stroker engine.