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I bought a cast set (not CNC) of Z1 58mm upgraded throttle bodies, matte finish, and the passenger side is a little fubarred, in my unprofessional opinion. Prior to swapping over the OEM return springs and idle adjustment screws, the passenger side butterfly valve would not close completely and would also stick with only a mild twisting force from my thumb and fore finger. The driver's side would shut closed fully, as if it were hitting a solid stop, almost like a snap, just like the OEM feel. The passenger side felt mushy when it reached it's closed position and even sounded different. I tried all sorts of minor adjustment and repositioning of the butterfly valve itself, even swapped parts with the driver's side (which showed no issues). The problem was always with the passenger side, indicating to me, there was a problem with the inner bore, perhaps misaligned or from core shift, but beyond my pay grade anyways. I contacted Z1 about the issue several months ago to see if they had encountered this problem before and they insisted they had not. Because I bought these second hand, albeit new, they could do nothing for me. I figured it would be an easy fix with a little sanding/polishing and put off the project until last weekend when I finally had time to install them on my plenum. After attempting to reshape the inner bore with a combination of sandpaper and a wire wheel and drill, I've improved the amount the butterfly will close, but it still sticks, perhaps even more so. Now that the return springs are in place and the throttle bodies are installed on the plenum, snapping the valves shut by rolling the throttle open with my thumb, then releasing, results in a stuck butterfly valve that requires quite a lot of pressure to open again. Yes, the travel limit screw could be run in to keep the valve from reaching the point where it sticks, but at what cost to the idle? The amount of light that passes between the butterfly valve and inner bore is significantly more than on the driver's side, which closes fine with no stick. The OEM's seal completely, allowing no light to pass through, but do have the grove cut in the bore at 6 o'clock, so I don't know if my seal argument carries any merit. I wasn't sure if this gap on the passenger side would cause me idle problems, until Evan (Wright Ca) posted that he had similar problems with his Z1 throttle bodies which had in turn caused him idle issues. After Evan chimed in, Ztuner spoke up. Anyone else?
WARNING: I lack industry backing
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11:28:16 05/10/11
