355 Bypass rattle repaired

Discussion in '348/355' started by kenneyd, Jan 9, 2020.

  1. kenneyd

    kenneyd Formula 3
    Silver Subscribed

    Sep 30, 2014
    NE FL
    Full Name:
    Like many of you, my bypass valve would rattle at idle. I tried adjusting the preload tension, but to no avail.
    I ended up installing a capristo twin sound for a while. While the twin sound was on my car, I figured I'd cut into my bypass since i considered in junk anyway.
    I had seen another valve cut open up here, it used a single ball bearing to center the shaft, mine was different, The cap contains a spring that holds a ceramic cone that centers the shaft.
    I initially tried to copy the capristo design, I bought 10 ceramic bearings and used the spring and a washer to press against them. This worked for a little while, but ended up seizing.
    So i gave up on modifying it and installed cleaned it up really good. I used some light sandpaper to remove carbon buildup so the ceramic cone fit in the valve housing better. I then used graphite dust to lube it thoroughly and reinstalled.

    I've been using it for 3 months now, no rattles.

    Might be worth a shot before buying a new one.

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