<BLOCKQUOTE>quote:</font><HR>Originally posted by TJS69:
Eric 68 - I agree with what you are saying about advancing/retarding a cam but here is some food for thought. Suppose the XE-256 was designed for a 350 and not a 327. The stock 350HP 327 cam was retarded 4* at grinding. If the XE-256 was not, wouldn't retarding it in a 327 be beneficial? Desktop Dyno shows improvement, anyone with real life experience on this?
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OK, there's a lot of things that could be changed with a grind to make it better for one size engine. If you have to change around the cam timing to make a cam work with a particular combo, there is probably another cam that will make even more power without messing with timing. Look at the XE 262 or XE 268 with your 327 example. Retarding a cam to make more peak horsepower has serious consequences - look closely at what happens to your torque down low. As you start retarding a cam significantly you'll also see torque fall, dip and look "not so smooth" below say 3000 RPM.
If you keep making more power by retarding a cam you should probably look at a couple cams with more duration. More duration will open the intake valve sooner and keep it open longer so you can fill the cylinders better. When you retard a cam you are not keeping the intake valve open any longer, you are just delaying its opening and closing points. It's OK to change cam timing around a little (4* or less IMO) but you had better know why you are doing it and the consequences it will have on TQ.
Another example, Lobe Separation Angle is the angle between the centerline of the intake and exhaust lobes. You were talking before about advancing and retarding the entire cam before, but if you get a cam with a wider LSA (say 112 degrees instead of 110 degrees) you are effectively changing just the exhaust valve timing if the cam is installed on the same intake center line (not advanced or retarded). A narrower LSA will open the exhaust valve sooner and create more overlap with the same duration. This generally creates a narrower power band slightly higher in the RPM band. I mention this because longer stroke engines (you mentioned going from a 327 to a 350) generally like a tighter LSA where shorter stroke engines work well with a wider LSA. A wider Lobe Separation Angle generally creates less peak power but creates a wider RPM band that fits well with smaller cube engines.
As you can see there is a lot to picking the right cam.
[This message has been edited by Eric68 (edited 01-25-2002).]
