LS1 Heads and Cam Info - Blackcamaro.com
| Following is info I've found in my search for a Heads and
Cam. It is my understanding based on a lot of research, can't
guarantee every tidbit of info is 100% correct but hopefully it helps. Heads: Stage 1, 2 and 3 doesn't mean much. Sometimes they relate to valve sizes, sometimes they relate to double springs, you get something more than the previous stage, that's all. They typically all include a 3 angle valve milling job for better flow. Valves: 2.00 or 2.02 intake and 1.57 exhaust is typically Stage 1, but others have this on stage 2 and even 3. This is the size (diameter) of the holes for the respective valves. Basically means you can push more air through your engine, this is where the power comes from. 2.055/1.60 is typically Stage 2 but again no real relation. Even bigger valves means you can push even more air through. Larger valve seats are required, the factory ones won't take this size, so that is part of the additional cost. 2.08/1.60 is even bigger on the intake, but this seems too big for stock bore engines, better flow on the bench but can cause problems on the car. Doesn't seem to line up well with the stock bore diameter. Again larger seats would be required for this. Higher stages typically buy you new hardened valve seats (instead of stock-ish ones), maybe valve seals, bronze valve guides, better quality valves, better springs, etc. Camshaft: Duration (2xx/2xx) means how long the valves are open with each rev of the camshaft. Longer valve opening time usually means more power to a certain extent but you can go overboard. Duration also will increase emissions. There are split cams where the second number (exhaust valve duration) is bigger, this is usually for super/turbo/nitrous, since your intake is now more efficient than your exhaust, so it keeps the exhaust valve open longer. Reverse split is becoming popular for naturally aspirated, since our cars typically have very good flowing exhausts and the intake needs some extra help to keep up. The first number (intake) is larger on this type. Duration seems to affect the width of the powerband. Duration is a measure of degrees but I can't figure out exactly how it is measured. But one way to look at it is the width of the lobe. Lift (.5xx/.5xx or .6xx/.6xx if you're nuts) seems to be the point where the most power is available. Doesn't seem to affect emissions much but allows more air to go in and out in the same period of time. Higher lift necessitates better springs, since they are moving a lot more in the same amount of time and compressing a lot more. Broken springs can ruin your engine, so duals are a very safe bet. Lift seems to push the middle 80% of your HP/torque curve upwards. Lift is measured in inches, the height from the core of the cam to the top of the lobe. LSA is the angle between the intake and exhaust lobes. This determines the time between when the intake valve closes and the exhaust opens. Too small and you get overlap, where they are both open at the same time and you can get fresh air and exhaust mixing (that's bad). Duration and LSA coupled together cause this. Lower LSA typically moves your power down a tad in the RPM range, higher moves it up. ID is timing ground into the cam. Personally I'd rather let my adjustable timing chain do this job, but many order theirs with -2 or -4 timing, if you don't have an adjustable timing chain this can gain you some extra power, and -2 and -4 don't seem to cause any problems with the car that I've read about, in fact -2 seems to be what a lot of people order by default. Like I said, the adjustable chain makes it a lot more flexible and less permanent. LSA and Lift affect the "sound" and idle quality of the car. 112 LSA even with a moderate lift can cause stalling or sputtering, especially on an A4 car. Camshaft Basics: -Lobes are the bumps on the cam that indirectly push the valves open
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