I found some info on the factory camshaft for my 283, the chart has a duration including ramps of 300 degrees and 250 degrees excluding ramps. I assume the 300 degrees would equal advertised duration and the 250 degrees would be at 0.05 lift. Please someone correct me if I am wrong. The chart does not state what including or excluding ramps actually means. I first thought 300 degrees was a little excessive but then I remembered that the 283 is a short stroke high revving motor so that probably isn’t that excessive.