I’m working on a pair of cylinder heads of unknown history. One head has channels (on both intake and exhaust) milled into the bottom leading up to the rocker bearing bores as well as material machined away (to form a trench) from the side to encourage oil to flow into the channel. The trench on the intake is on the rearward side of the bore and the trench on the exhaust is on the forward side. The other head, bottom photo only has the machining done to the intake side. They are both front heads. I also have a NOS head that just has the machining done on the intake side. It was done at the factory before the the guide was installed. Does anyone know for sure what the last batch of heads looked like? Did the factory eventually put the drainage on both intake and exhaust? Front head as well as rear?
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