I had an idea to modify a D series engine to perform more like a atkinson engine where the valves close a little bit after the piston travels from BDC towards the top. I also read that people have noticed fuel economy improvements from simply advancing their cam timing, but I think this could only apply to city driving since more fuel in the combustion chamber wouldn't help with cruising at highway speeds, unless someone can point out how it still would. Either way, my idea would be to know how a cam could be machined so that the valves stay open longer, effectively advancing the intake valve opening while retarding the valve's closing as well.

Anyone know of the type of a machine shop I would go/call, how I'd get them to do it and how much it should cost? I know nothing about this sort of thing but am interested in it.

Is this the same thing as running an aggressive cam like they do on race cars? It sounds like it but at the same time, from what I read you have intake and exhaust valve overlap, leading more emissions but possibly more power.


Modified by imzjustplayin at 12:11 AM 7/12/2008