THE BIG-BLOCK FROM HELL cont’d
Lunati supplied the Pro Series BB421KN forged steel crankshaft. This crank features a 4.375-inch stroke, and
standard 2.750-inch main and 2,200-inch rod journals. The crank was balanced at Paul Pfaff Racing using bobweight
data specified by DNE. If you look closely, you’ll notice that there are two oil pan bolt patterns drilled in
the rail, and one of them has been plugged. This is because we picked up an oil pan that was originally destined for
a Donovan C-500 block for a song and had to drill that pattern into our block in order for the pan to work. We got a
great deal on the pan, so the extra labor was worth it.
The 55mm roller cam bearings are from Timkin. Unlike other blocks, Brodix provides spiral steel locks to keep
the bearings from moving after installation. We test-fit the locks before deburring the block, and they were actually
quite easy to install, even in the No. 2 and 3 journals, which are difficult to access.
The camshaft is a very aggressive mechanical roller, spec’d out by DNE and ground by LSM, that features
the popular LS firing order swap, which alters the firing order of No. 2 and 3 cylinders and also No. 4 and 7
cylinders. According to Ebbert, who checked the camshaft after it arrived at the shop, the swap can make aditional
power with the right intake manifold and header combination. Dave had the camshaft custom-ground for this application
and was remiss to mention the specifics. But, he did say lift at the valve measured more than 0.800 inch for both
the intake and exhaust, and that the duration for the intake side was 270-plus and exhaust 280-plus degrees. The
lobe separation is at 116 degrees.
The other half of our rotating assembly is comprised of parts from CP, Lunati, and WPC. The forged CP pistons
feature lateral gas ports, a 1.300-inch compression height, and -0.180-inch dish. The ring grooves measure 0.043-inch
up top and 1.5 mm for the second groove. The piston skirt also received an anti-friction coating from Embee. The forged
Lunati Pro Billet connecting rods measure 6.700 inches long, and the small bushed ends swing on Western Wristpin 4340
chromemoly wristpins. The 0.990-inch-diameter wristpins have a 0.180-inch tapered wall. The wristpins also feature a
proprietary metal treatment process that, according to Ebbert, does increase the strength of the metal, considerably.
Akerly & Childs moly rings make up the pack. The narrow top groove is filled with a 0.170-inch radial wall
ring. Groove No. 2 received a Napier hook groove ring with a 0.165 radial wall.
The machine work on these rods is incredible, and they only needed a minor touch-up on a polishing wheel to
bring them into near-perfect balance. The small ends are bronze bushed, and the big ends are held together with
7/16-inch hardware from Lunati. The rod bolts were tighened, and the stretch was measured against Lunati’s specs
rather than relying on a torque spec.
A crankshaft scraper was employed to keep oil off of the crankshaft as it rotates, which will reduce windage
and increase horsepower. It’s held snugly in place, via the oil pan mounting bolts. The scraper was designed
by DNE and Jordan Woods and is laser-cut from 0.040-inch stainless steel.
A Titan Speed Engineering Sportsman wet-sump oil pump is coupled with an MSD oil pump drive unit (12a). The
Titan pump is a gerotor design that virtually eliminates high-speed cavitation, is fully rebuildable, and incorporates
a large built-in pickup. The MSD part was necessary to connect the oil pump to the cam gear, because we’ll be
installing a Jesel front mount distributor, rather than a traditional distributor.
Dave had to machine some material off of the oil pump’s case to provide adequate clearance for the No. 5
crankshaft counterweight. Once he was through making aluminum chips, the pump fit perfectly (12b).
Stef’s Fabrication Specialties crafted the 14-quart, kick-out-style oil pan from 0.090-inch-thick
aluminum that we’ll use to seal up the bottom end of this motor. The pan features a Teflon-coated, uni-directional
windscreen, designed to allow oil to flow into the sump area but not splash back up out of it toward the crankshaft.
The pan also contains a pair of trap doors that keep the oil in the sump area during hard acceleration. A generous
amount of gray silicone sealant was used to mate the oil pan to the block, rather than a traditional gasket. Care
was taken, here, to make sure not only that oil wouldn’t leak out but that the crankcase was completely sealed off
to allow the vacuum pump to do its job.
—courtesy Sport Truck magazine; Photography: Mike Finnegan
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