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In checking with the Tech's at the Lexus dealership where I work, his statement is absolutly correct. The reason there is increased HP for the GS over the LS and SC is due to the increased flow. The LS is designed to be a quiet/smooth riding car. If Lexus did not put noise surpression into the exhaust it would be too loud, and this causes it to loose HP. My understanding of the SC is that it runs a tighter stock exhaust then the GS. It si shorter and more conjested.
There are companies that will take a stock camshaft and make it bigger either by welding or grinding a smaller base circle (both have long term wear problems) and if someone could overcome the stock rev limiter, fix the flow to tolerate higher valve lifts and do the other suggestions we could see an engine that will increase power to 7000+rpm. All in all more work for less than supercharging or turbocharging.
Going to have to disagree with you on this one. There is an old mistrust with regrinded cores that comes from the old detroit steel days.
When the good ole boys ran a regrinded camshaft in their big block they were noticing that they would flatten out a lobe sooner than they would with a new core cam. This was due to their cam springs being around 500lb VS. the overhead cam designed springs (roughly 200-300 lb).
Havent seen flow charts on the 2JZ GE head yet, but I am very interested to see the results. Upgrading springs and retainers when increasing lift is always a necessity and will help keep your head healthy when you exceed the 7K mark. I have never heard of a case where increasing lift decreased the total flow of air. I would be very interested in seeing something on this, where did you get this info?