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Been trying to figure out the dip at 6600 in my dyno graphs. So I went Friday and did a test on the 1.85s and swapped back to stock rockers on the dyno (it was hot) and here are the results. Red is yellaterra 1.85 and blue is stock. I have PSI1511 springs and titanium retainers on it. Mods are in signature.
That gain above 6k with the 1.85's is pretty good, until 6600. Too much rocker weight to control them properly at that rpm with those springs?
Thats the best we can come up with. These rockers are only good to 400lbs open spring pressure. I have heard they do fin up to 450lbs. I am currently looking for the ideal spring to swap and keep for a cam change. Need a decent amount of seat pressure but not to much to pop the head of a valve off lol
Thats the best we can come up with. These rockers are only good to 400lbs open spring pressure. I have heard they do fin up to 450lbs. I am currently looking for the ideal spring to swap and keep for a cam change. Need a decent amount of seat pressure but not to much to pop the head of a valve off lol
I gotcha. It's interesting that it looks like the stocker's made more power down low, but the 1.85's gained ~15whp up top.
Considering I am never below 5k I dont know how the rockers would not be faster on track. The gain up top is a solid 10-12 until 6600.
Maybe I wasn't too clear - I meant that with the new short runner fast you're going to run you'll want to be shifting 7500-ish. This thing is taking a nose dive above 6600. Stable valvetrain and the short runner intake would probably run better on track than the 1.85's keeping it out of valvefloat. The fast intake makes less power until ~6000 rpm on an ls3.
I know you probably dont want to spend this kind of money, but to gain back the stability that you lost, your going to have to lighten up the intake valves and valve springs if you dont want to find lighter rockers. the weight of the springs themselves actually makes a difference. I'm sure you already have titanium retainers, if not then definitely get some. the little things add up. Before pulling the heads, try the external things.
That’s clearly a loss of valvetrain control up top. But what are your cam specs? Higher ratio rockers do increase actual valve duration slightly - I wonder if extra overlap is what’s causing that power loss - and that is a significant power loss.
09-17-2018, 07:22 AM
LS3 1.85 Rocker Test 
