primer84z

how much duration or lift is required to get that badass lopeing, lumpy sound from a 305. around 500?

Sitting Bull

It's overlap that causes the lope at idle and it isn't even a desireable thing, except that people have associated it with high performance from back in the 60s.

It came from the time when it required 300 degrees of duration or more for the lobes on the cam to support the amount of lift used to generate that extra hp. That meant that both valves were being held open at the same time, thus the "lope" as the exhaust gases returned through the intake valve and on into the intake manifold in extreme cases. Since modern cams have a great deal more science backing them up--stiffer springs, computer designed lobe profiles, etc.--loping at idle is simply not as pronounced as it once was.

My advice is to simply contact your cam manufacturer, explain what you want for performance and take their advice. If you get a lope out of it, consider it icing on the cake. Knowledgeable engine builders know a lope is not necessarily the sign of a wicked motor. Oftentimes it only signals an engine with very poor low rpm performance

87-ZMAN

it doesn't take that much for a 305. I have an slp roller 214/224 duration and it has a decent lope. it sounds even better with headers and free flow exhaust, which you should have anyway before installing a high performance cam.

rx7speed

a lumpy idle doesn't mean better

you might even go slower