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Horsepower RulesNelson Racings 740-Horse Small-Block From the February, 2009 issue of Chevy High Performance By Bob Mehlhoff Photography by Bob Mehlhoff, Ed Taylor
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 Nelson Racing has found that...  Nelson Racing has found that impressive power numbers rely on the right camshaft and cylinder head combination. So Nelson uses a special street mechanical-roller camshaft with about 250 degrees of duration (@ 0.050-inch lift) and close to 0.600-inch valve lift. Special opening and closing ramps help this engine combination sustain over 500 lb-ft of torque through mid and upper rpm ranges, but he wouldnt tell us more than that.  Since lots of horsepower is...  Since lots of horsepower is all about aerobics, Nelson Racing focuses on the cylinder heads. Tom Nelson starts with a pair of Dart 230cc iron heads and applies a special bowl blend. First he works the valve area to achieve a very thin 45-degree seat to each combustion chamber. Directly below that he blends a radius. To maintain good breathing, he opens up all intake ports to match a Fel-Pro 1206 gasket. The rockers are Crane rollers with 1.6s on the intake, and 1.5s on the exhaust.  To make power with reliability,...  To make power with reliability, Nelson Racing uses a full set of Scat connecting rods, SRP forged blower pistons with Total Seal gapless second rings, and a Cola 4340 forged-steel crankshaft. Before assembly, all reciprocating components are balanced for smooth operation. Because extremely accurate clearances are especially important with over 700 hp, Nelson uses Clevite H-series main and rod bearings. These special bearings use a thinner top layer of tri-metal to provide less material deflection and added fatigue strength.   Roots blowers dont like...  Roots blowers dont like restrictions on the inlet, so Nelson adds two 600-cfm Holleys prepared by the Carb Shop to a Blower Shop 6-71 supercharger. The pulleys run the blower at 15 percent overdrive with 9 pounds of boost. The engines peak dyno number at 7,400 rpm is 740 hp. Peak torque occurs at 5,000 rpm measuring 570 lb-ft. But whats really astounding is that the engine produces over 500 lb-ft of torque from 3,000-7,500 rpm.  To achieve optimum combustion...  To achieve optimum combustion efficiency, the block is machined for zero piston-deck clearance. For blueprinting purposes, the camshaft is degreed to spec and a Cloyes true-roller timing chain is installed. Underneath, Nelson adds ARP fasteners and four-bolt caps for strength. CHP Building engines is a numbers game. Compression ratios, cam specs, clearances, and cylinder-head flow numbers are all part of that equation we call horsepower. Unlike most other performance numbers though, the goal with horsepower is to have the highest number possible. Thats what Nelson Racing has been busy doing. The company applied its magic to a 383ci small-block and pumped out 740 hp. The engine now powers Rick Logstons 55 Chevy pickup around the streets of Bakersfield, California. How did Nelson get that kind of horsepower? Lets take a look.
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Carb Shop
Ontario
CA
9-09/-947-3575
customcarbs.com
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Nelson Racing Engines
9318 Oso Ave.
Chattsworth
CA
91311
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