The hole on the top rear of the head (where your heater supply hose is attached) is used on big trucks to supply flow from the hottest area of the head back to the water pump. Most small truck heads don't even have that hole drilled and tapped. The line on the big trucks was metal, not rubber. That said, this arrangement probably works well and would prevent trapped air at the back of the head.
The valve cover was designed for a PCV equipped truck, not a draft tube equipped engine like yours.
Last edited by Bill Hanlon; 06/06/2025 12:29 AM.
'57 GMC 102, Original 347 V8, HydraMatic, 3.08 rear gear, added A/C, disk front brakes, HEI, AFB carb, '98 Honda Black Currant paint. T-boned and totaled 10/12
'52 GMC 152 Stake Bed, Original 228, SM420, added A/C, HEI, disk front brakes, '67 Chev 3.55 rear gear. Gets used as a real truck.
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