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| With a bit of imagination you can make out the seats for the exhaust valves - the intakes (both seats and valves) were fine. Conventional wisdom has it that on these heads you don't need seats to handle unleaded gas, but in my case one or two of them were recessed anyway so I had new ones installed. Since I needed new exhaust valves too, I upgraded to the stellite-faced (harder) version. If you look at the fourth pushrod tube from the left you can make out where its end is flared - they're all like that but it's hard to see in the picture. Also visible are the bottom of the new guides; the original ones were cast iron and were well worn. See how the bottoms of the exhaust guides are more or less flush with the surface, yet the intakes hang down quite a bit. In this picture you can see how the combustion gases are compressed toward the spark plug as the piston nears the top of the cylinder - they kind of get squished over there since there is basically no combustion chamber on the port side. Head tuners recommend taking off the flat area with its sharp edge and tapering it instead; I guess the gases flow over toward the plug and valves in a more efficient manner. This picture also shows some ragged looking edges on the curved water jacket slots. I thought about opening those up a bit but the head gasket only has a small hole that lines up with the centre of each of the slots, so it's either open up the head gasket too or leave both alone. |