It seams that nearly every off the shelf cam comes with a ground-in 4 degrees of advance. Every single engine combintation that I have simulated on Desk-top-Dyno shows best power with 0 degrees of advance (about 20-40 hp better than with 4 degrees of advance). The dyno curves also show very very little low end loss at 0 degrees of advance.

So what gives? If Desk top dyno has any accuracy, why are all the cam manufactures recommending installing them 4 degrees advanced? Am I missing something here? Is it not done because of a reduction in idle quality?

 

the cam grinders don't recommend you install a cam advanced, or retarded any more than straight up. they grind 4* advance into a cam to make more torque. i'd install the cam straight up with the 4* advance ground into it. you'll make the most HP with the cam installed at 4* retard. DD isn't known for being greatly reliabler either, more of a good guess sort of thing.

 

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Cam grinders design their cams to be installed with the intake lobe centerline at a particular angle with respect to the crank rotation. It is pointless to get all worked up about whether the specific angular relationship the mfr calls for happens to be "advanced", "straight up", or "retarded" from the stock angle.

In other words, use the right timing set, put the cam in using the timing set's "0" mark, and the cam will come out where it was designed to come out. It's a waste of time trying to pick apart whether that's "advanced" or whatever, compared to where some other cam was designed to go. It's meaningless. So: if the cam was designed to go in with the intake center at 106°, then put it in at 106°, and don't bother whether it's "advanced" or whatever.

 

If DD2000 is showing a big difference by advancing or retarding the cam 4* either way, you either have too big of a cam, or too small of a cam for the rest of the combo, be it heads, intake, carb, exhaust, etc.

David Vizard points this out in many of his books, including one about dynomometer simulation software.

You should worry more about choosing the right cam, not making the wrong cam work better.