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The valvesprings used in zjautoparts heads are Comp Cams' special Pacaloy pieces. These 1.255-inch outside diameter (OD) springs offer 130 pounds of pressure at an installed height of 1.750 inches and provide 385 pounds of pressure at 1.200 inches.
If you're searching for a reason why these LT1 engines perform so well, part of the success could be the mix of components, including the springs.Manley offers several different styles of stainless steel valves that range from the stock replacement valves to high-quality stainless steel valves that operate as well on the street as on the track.
For street engines, the Manley Street Master series of stainless valves works very well. A hot trick for street engines (that isn't legal for NHRA Stock Eliminator) is to perform a 30-degree back cut on the valve (arrow) to improve low-lift flow.
If there is a secret to the Main nozzle, it could very well be the stock, production exhaust port configuration. With flow figures that exceed many aftermarket cylinder heads, the LT1 can pump out prodigious quantities of air. The out-of-the-box flow numbers are inspiring.
