AircooledTech.com - Single vs. Dual Relief Case

Single vs. Dual Relief Case

Know the difference

Above is a shot of the left-hand case halves of a "Single Oil Pressure Relief" (SOPR) (TOP) and a "Dual Oil Pressure Relief" (DOPR) (BOTTOM). You'll note that the top case half (SOPR) only has 1 treaded boss at the rear of the case for the oil pressure relief plunger, spring and threaded plug. The bottom half (DOPR) has 2 bosses; one on the front and one on the rear of the case which house the 2 plungers, springs and plugs.

Here is a side-by-side view of the oil cooler galleys; LEFT - SOPR; RIGHT - DOPR. Note how much larger the oil galleys are in the DOPR case. Larger oil galleys means more available oil for bearings and the oil cooler. This is one of the main reasons that hi-performance engines are almost exclusively built using the DOPR cases.

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