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 Big-Block 502 ci 1. COMP 1.7:1...  Big-Block 502 ci 1. COMP 1.7:1 Ultra Gold roller rockers are CNC-machined to withstand extremely aggressive spring pressures and maintain accurate rocker arm ratios. 2. KB flat-top hypereutectic pistons for 4.500-inch bores are lightweight with rigid-rib skirt designs, which stabilize the piston in the bore. The pistons are also 390 alloy and heat-treated to T6 standards. 3. Proform-fabricated (clear) aluminum valve covers weigh just less than 1.5 pounds each and include recessed Bow Tie and Chevrolet emblems inlaid with classic Chevy Red. 4. The Weiand Stealth (oval port) dual-plane intake manifold has long separated runners for increased torque and makes power from idle up to 6,000 rpm. 5. The MSD 6AL-2 ignition box includes a new housing with digital controls. Rev control adjustments are made via four rotary dials in 100-rpm increments. It also offers higher output, with up to 135mJ and 535 V.  Big-Block 540 ci 1. SRP inverted...  Big-Block 540 ci 1. SRP inverted dome forged pistons. 2. The 8-inch TCI harmonic balancers are SFI approved to 12,000 rpm. They include a superstrong billet steel inertia ring for longer life, and a high-quality bonded runner eliminates outer ring movement. 3. Proform-fabricated (black) valve covers offer welded billet mounting rails for leak resistance and are 45 percent lighter than comparable stamped-steel die-cast covers. 4. The Weiand Stealth (rectangular port) dual-plane intake manifold offers good bottom-end torque with a special runner design and larger plenum for extra flow. 5. Fel-Pro 1075 MLS gaskets feature a solid-steel core to minimize gasket blowout. For extra sealing force, a preflattened steel-wire ring combustion seat with stainless steel “armor” is added around the combustion chambers.  Using a 4.500-inch piston...  Using a 4.500-inch piston ring compressor, Rode made his rounds and plugged each bore with the completed rod and piston set. Each rod was attached to the crank journal using a 7/16-inch ARP cap bolt.  Back at JMS for round two,...  Back at JMS for round two, we hooked up the new stroked mill to the dyno; this time with more cubic inches under its belt. To compare just what the mill would produce with only the addition of the 540 stroker kit, we’ve left the crate ZZ502 aluminum cylinder heads up top with the same roller camshaft, lifters, and 1.7:1 roller rockers. Our efforts were worth 553 hp at 4,800 rpm and 648 lb-ft and 3,200 rpm.  By The Numbers Cylinder Heads: Bow Tie 502 For baseline runs of the freshened 502ci mill and stroked 540ci engine, we utilized a set of GM ZZ502 cylinder heads (PN 12363392). They come with 290cc oval intake ports and 110cc exhaust ports with equal-sized combustion chambers. While they can be purchased complete as off-the-shelf pieces from GM, JMS Racing performed a small valve job by installing larger, 2.250/1.900-inch intake/exhaust valves and heavier-duty COMP dual valvesprings. Cylinder Heads: Dart Pro 1 While we got our set from Dart Pro 1 cylinder heads as a bare set, Aerohead Racing Components performed the custom assembly for our 540ci stroker build. Race-proven features and affordable pricing make these Dart Pro 1 355-T6 aluminum cylinder heads one of the biggest values in racing. The Pro 1 cylinder heads feature 119cc combustion chambers and larger, 325cc intake runners with 129cc exhaust runners. Aerohead’s team added 2.300/1.880-inch intake/exhaust stainless steel valves, Aerohead spring cups, hydraulic roller 1.550-inch dual valvesprings (354 lb/in), and 10-degree split locks with Viton seals. ARP 7/16-inch rocker studs were also installed along with Dart adjustable guideplates.  Round three at JMS involved...  Round three at JMS involved swapping out the factory crate engine cylinder heads in favor of the more efficient flowing Dart Pro 1 heads with the Weiand intake (rectangular port). Everything else, including the COMP valvetrain remained the same. We’ve even left the same Holley 950-cfm carburetor. Although our gains were minimal, it was clear that the current camshaft was too small to take advantage of the heavier-breathing Dart Pro 1. On JMS’ dyno, we peaked at 558 hp at 4,800 rpm with 641 lb-ft at 3,900 rpm.  It was obvious our stroker...  It was obvious our stroker 540 was running out of breathing room with the smaller camshaft from the 502 testing. To take full advantage of the Dart Pro 1 superior flow, we swapped in a higher lift cam with more duration. Our new Extreme Energy camshaft (XR294HR) came as a complete kit with timing set and even included new retrofit hydraulic roller lifters. The lifters not only decrease friction over flat-tappet designs, but these will accept much more aggressive cam profiles. Our camshaft spec’d out with a duration of 242/248 intake/exhaust at 0.050 inch with 0.540/0.560-inch intake/exhaust lift and was good to 6,200 rpm.  Our final round with the 540...  Our final round with the 540 at JMS proved to be well worth the effort, considering this is where we made the most gains across the board. The choice to swap out camshafts maximized the flow of the Dart Pro 1 cylinder heads, and the engine picked up 100 hp and nearly 80 lb-ft from initial baseline testing. On JMS’ dyno, the stroker 540 produced 592 hp at 5,000 rpm and 648 lb-ft at 4,500 rpm.  The Parts List Holley’s HP-Series carburetors include updates to their traditional line of 4150-style pumpers. These updates include cast main bodies without choke horns and smoothed venture transitions for increased airflow. Since they’re aimed directly at optimizing power and performance for racing applications, other important modifications include screw-in air bleeds, stainless steel throttle plates, and notched floats. Holley also has Dominator-style fuel bowls to allow fuel line plumbing from either side. All of our 502ci and 540ci testing used the 950 HP for dyno pulls at JMS. CHP
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