I also want to know whether or not the Pontiac Factory cut the valve seat Boss on the Exhaust Valves, intending using the positive seals, with the two metal straps or was that done after the Engine left the foundry using their meticulous machining process? The reason I ask is to ascertain whether or not the Heads were modified before or after leaving the Factory. Why does the factory use the Umbrella seals? They machined the Heads better from the factory compared to other manufactures, or so I read.
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