360 head porting for big power (500HP ?)
Now the exhaust side. This is where the 308 shines. From what I've read over the years is that the 308 ex. port was inspired by the W-2. The port is a drastic departure from the older designs. The floor is raised up into a proper shape, yielding an excellent broad short side. Even though the port exit looks small it flat out works. I can tell you from personal experience that opening up the port at the exit to gasket size will kill the flow.
.......ex1.......ex2
.050--21.........21
.100--46.........45
.150--73.........70
.200--92.........87
.250--117.......108
.300--137.......126
.350--156.......139
.400--169.......150
.450--178.......159
.500--182.......162
.550--184.......163
.600--184.......164
ex1-out of the box with OEM valve flowed with 1.75 pipe
ex2-out of the box with OEM valve flowed with out pipe
guide ground flush with roof
Now the exhaust side. This is where the 308 shines. From what I've read over the years is that the 308 ex. port was inspired by the W-2. The port is a drastic departure from the older designs. The floor is raised up into a proper shape, yielding an excellent broad short side. Even though the port exit looks small it flat out works. I can tell you from personal experience that opening up the port at the exit to gasket size will kill the flow.
.......ex1.......ex2
.050--21.........21
.100--46.........45
.150--73.........70
.200--92.........87
.250--117.......108
.300--137.......126
.350--156.......139
.400--169.......150
.450--178.......159
.500--182.......162
.550--184.......163
.600--184.......164
ex1-out of the box with OEM valve flowed with 1.75 pipe
ex2-out of the box with OEM valve flowed with out pipe
guide ground flush with roof
