1hot12c: What I was woried about when I made that statement about not putting the rockers into an LS2 was loss of control of the valves at high rpm, and the effects of long term stress when using the higher ratio rockers to further radicalize an already hot cam. The LS2 spins up to 6500 rpm! I hate it when someone comes to me and says "you said (or implied) I could do this and it would be no problem".
The part that particularly scares me is that valve springs for example will handle an over-stress for a while, (like during an initial dyno pull after the install) but then begin to allow float after visitng those revs a certain number of times. Once you float at 6500 rpm, bad things can happen pretty quickly, and unplanned inertia loads appear. It is inertia loads that cause failure in modern engines.
I am not surprised that several different combinations apaprently led to similar results. Usuall, that means that there is a "cork" somewhere in the system other than the components being swapped, so as long as any specific combination of components exceeds the flow capability of that cork, ANY combination will be fine - until you find the cork and pop it out, at which point the individual combinations get a chance to strut their effectiveness.
This is precisely what happened on my LM4. The initial dyno tune, less the artificial loss due to stiffer gearing (inertia effect - see earlier psotings or my book) gave me 8 to 18 hp depending on which dyno run you believed. The headers were good for mid range, and so was the dual exhaust, but since the cam was stifling the engine above 4000 rpm, we picked up only 20 hp at peak. Once we popped the cork (the cam in my case), we picked up 58 more horsepower instantly. Since that cam is normally only good for 32 to 33 hp at rear wheels when done alone, we proved the cam was the cork.
The Z06 cam grind and Z06 valvetrain in my LM4 is the same one I ran on my factory stock 2002 Z06, and so I knew it was dependable before trying it on the LM4. My SSR is NOT my weekend / good weather toy: it is my ONLY transportation (my wife drives our Mazda Tribute SUV daily). My choice of mods and components therefore reflects a strange combination of 38 years of aggressive hop-ups coupled with the knowledge that going just a bit too far can leave me stranded halfway across the country on the way to a consulting assignment, and having to explain to my wife why the blown up engine is not covered under Chevy warranty.
In this specific case of my SSR, I knew I was duplicating my Z06 except with inferior heads and very slightly inferior manifold, but better exhaust (headers AND true dual), plus I had read Will Handzel's book, so I knew I was on safe ground. As it turns out, the 5.3 liter displacement and this particular set of mods is one of those “magical combinations” that performs better than it “should”. At 6000 rpm and above, the gains in horsepower over stock exceeded 100, and at 6500 rpm, the gain was 123 horsepower. If you know how correction factors "work", getting 331 hp at the rear wheels is a miracle when the temperature is 95 degrees, the humidity is so high it is RAINING, and the barometric pressure is the lowest I had ever dynoed at.
I haven't yet looked at that link you posted, but will do so tonight! I am always looking for more knowledge! And, I like it when it is someone ELSE's money and engine finding that knowledge!!
Jim G
