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Welcome to Camcraft Cams
Important technical info for lift rule classes...
We have had some problems with customers not being able to get enough rpms from low lift profiles. This is usually due to not checking open spring pressure. The spring specs may state a sufficient pressure but it is usually for a much higher valve lift.
...Be sure to check your actual installed spring pressure at both open and closed checking heights that apply to YOUR heads and camshaft. The open pressure is the most important.
On low lift applications it may be necessary to shim the springs to 20 or 30 lbs over the recommended seat pressure to get the right open pressure. Failure to do this may result in valve float and engine damage. DO NOT USE Z-28 SPRINGS! They will have a very short life and not enough pressure. We recommend H-11 tool steel springs, which cost about $160.00 per set. They are cheaper in the long run, especially if they prevent an engine failure. Some of the stock diameter valve springs for .550-.600 lift will work but they will still have a shorter life than the H-11 version. Remember these are race profiles and have very radical valve motion.
Good spring maintenance is very critical. Cams with dwell at Max lift (HDML series) usually have about a 6500 rpm limit.