Keep in mind that these are what I recommend for racing engines, but the
oil clearance you use depends on
oil viscosity. With that said, main-bearing
oil clearance should be about 0.0026 in. However, if a low-viscosity oil such as 0-20W is used to reduce pumping losses--not recommended for the street or long engine life--oil clearance should be on the tight side, or about 0.0018 in. But don’t be surprised with low oil pressures at speed. Ten 10 psi is typical on the high banks. Likewise, zero oil pressure has been observed in the lights with drag cars. In both cases, coated bearings allow the crankshafts and bearings to survive.