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Short Block
Like snotty-nosed shop apprentices, engines start at the bottom. The bottom for the 580 is a good one—a World Products Merlin III iron block. The tall deck (10.200”) block is CNC-machined with your choice of 4.290” or 4.490” as-cast bores; they can be finish-bored up to 4.625”. Combine that with a 4.375” stroke crankshaft and you’re talking 632 cubic inches, bunkie. The Merlin III block also features priority-main oiling (main bearing bores get oil before the upper engine), 4-bolt nodular iron main caps, blind-tapped head bolt holes for extra deck integrity, and larger water jackets for improved cylinder cooling. World even taps the vacuum scavenge lines for dry sump oiling systems. Here, the block gets a couple swipes with the milling machine to clean up the decks and make sure they are both even and parallel. This will ensure head gasket sealing—very important when you’re stuffing big boost into an engine.

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The milling machine is set with a dial indicator indexed to a fixture bolted to the front of the block. Kevin took .010” off each deck to get them nice and equal.

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The block is bored to 4.530” with torque plates installed. The plates simulate the torque applied to the block by the cylinder heads, ensuring the cylinders are bored so they will be nice and round when the heads are bolted on. If you don’t use torque plates during the boring process, the bores will distort (become out of round) when the heads are bolted on the block.

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The reciprocating assembly—Lunati Pro Blower Series billet steel crank, Manley Series I-beam rods, and JE forged pistons—was carefully weight-matched and balanced. Here, the small end of a rod gets weighed; each end of every rod is weighed to help determine the proper amount of bob weight needed for the balancing process. The Manley Pro-Series rods are machined from aircraft quality 4340 alloy forgings, are fully shot-peened, Magnafluxed, and weight-matched, and are fitted with super-strong ARP cap screw bolts.

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The JE forged pistons were also checked to make sure they all weigh the same; they were right on. Kevin custom-ordered the forged slugs with a 28cc dish. Combined with the 122cc chambers in the Trick Flow PowerPort cylinder heads, the pistons yield a forced induction-friendly 8.5:1 compression ratio.

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The Lunati Pro Blower Series crankshaft gets drilled for slugs of Mallory metal to help internally balance the reciprocating assembly. The Lunati crank is whittled from 4340 steel alloy and features cross-drilled mains for improved oiling, dual keyways in the snout (to better retain the crank pulley on a blower application), 7/8” lightening holes in the #2, #3, and #4 rod journals, and .140” radii on rod and main journals to reduce chances of fatigue cracking. The Pro Series crank requires narrow, chamfered main and rod bearings; Kevin sourced them from Clevite.

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The Lunati crankshaft and the bob weights after a spin on the balancing machine. Kevin ended up using three slugs of Mallory metal to balance the assembly.

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This shot gives you a good look at the crankshaft counterweights. Lunati calls the counterweight design the Contoured Wing; basically, the leading edges of the counterweights are shaped to direct air and oil to the main journals rather than the connecting rods. This helps reduce oil aeration and windage, which costs valuable horsepower.

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With the bottom end buttoned up, Kevin installed and degreed in the solid roller camshaft, custom ground by Steve Morris Racing Engines on a Comp Cams blank. Sorry, specs are top secret.

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Piston ring gap is critical on supercharged, turbocharged, and nitrous-urged engines. You want to open up the gap to create a controlled leakage of the incredible cylinder pressure caused by forced induction. If the rings are gapped too tightly, the increased cylinder pressure will literally bend or break the rings, causing very bad things like massive blowby, gouged cylinder walls, and possible engine failure. Kevin gapped the Total Seal rings at .032”(top) and .026” (secondary).

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