D0VE-C and prior castings






The major difference between the C8VE, C9VE, D0VE-C vs. the later D3VE and D8VE castings is the height of the short turn crest. The valve seat is .100" closer to the valve guide in the later castings and this is very  material to good flow.
The short turn crest is too low  in the D0VE-C's and prior years and had a concave shape. Do not lower the center any further. Do however lower and open the corners of the short turn where they meet the port walls. This allows flow to follow the floor rather than be deflected to the port center and causing turbulence.  Since the valve seat is so close to the short turn with the older castings you should avoid rolling the short turn right off the valve seat. Allow some distance before beginning this roll. .100" is about all you will get after the ridge in the bowl is blended back. This applies wether or not the seats have been cut for larger valves. Although the larger the seat diameter, the easier it becomes to have this straight shot off the seat before the short turn roll is begun.
click for the big picture
click for the big picture
As you view the short turn from this angle note the sweep from left to right. also note that there is about .100" distance before the roll to the short turn crest begins. As you look at this pic notice how the whole short turn look a bit like a funnel. I know this is very difficult to envision. There will be sections port pics in the near future.
Note the concave shape of the short turn crest. When rolling the short turn radius do not lower the crest. Stop your roll just before the top of the crest. Note again the gentle radiused sweep from left to right as the crest rolls down to the bowl and seat in this view.
click for the big picture
The distance to water on the right side of the guide is less generous on the early castings vs. the D3's. Follow measurment guides to the letter to avoid breaking through the water jacket. Because the D0VE-C and oprior castings have the valve seat .100" further from the guide / trench area so raising this area isn't quite as critical as with the later castings.
Thes are the primary differences to account for when porting your early castings. Look at page two for the lates update on the D0VE castings...
to page 2
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Follow these instructions carefully this is an important part of a good D0VE exhaust port.