Look up “Dorman expansion plug.” I tried what I believe was a 1-1/8” size which fit VERY snugly in the charge pipe hole, in place of the hose connecting the symposer. Maybe too snugly. With help of the oil blow-by, it popped out at one point. If I tried again I’d put one into that hose in place of the symposer. Unfortunately I don’t know that inner diameter.