This was a good thread and those are some nice videos. I thought I would contribute these two links, they expand a little further on some of the stuff discussed above. http://rehermorrison.com/tech-talk-70-airflow-fallacies-avoiding-the-pitfalls-of-the-flow-bench/ http://www.superchevy.com/how-to/exhaust/0505phr-exh/ This second article is a lengthy read and the portion of the article related to cylinder heads is about in the middle. The concept of the 5th cycle on a racing engine (or any engine relying on a camshaft with fairly heavy valve overlap) is really interesting. Like mentioned above small displacement import engines have varied valve timing, minuiplated valve overlap and utilized relatively low lifts to minimize the effects of revision with great results.
487, Thanks for that Vizard link. That guy putting long known OEM engineering knowledge into the hands of the enthusiasts has been one of the greatest gifts to the hobby of hot rodding. I get a bit frustrated seeing posts stating stuff like, "headers are only worth 5hp on (??? whatever engine)... not worth it", without any consideration to the compatibility of components, or the big picture. Vizard's articles are meant to be universal in principles, but he'll often give you just enough math to apply it to your own projects. One can certainly go much deeper into this with education, but with the advent of today's info sharing and online resources it's no longer a lifetime's investment to it. To me...this stuff used to be called "competitive advantage". Once a person gets a good grip on how this stuff works, I guarantee you'll chuckle every time you flip through a Hot Rod or Car Craft dyno test. The hobbyist today has one major advantage over a shop...they can spend as long as they need on something to achieve the results they want. I've met some very humble people with only modest equipment match or beat some of the most well known names in the business. That's saying something. Some are even on this board. If people want more that what mass produced stuff will get you, utilize the info sharing available and commit to making it happen. These ARE Nailheads were talking about here, not a lot being made for them.
