Technical SBC factory ram horns 2" vs 2.5"

At what HP range would see the greatest benefit to use the 2.5" vs the 2" ram horn manifolds on a SBC? (and corresponding sized exhaust pipes)

 

2" ~290-300hp.
2-1/2" ~475-490hp.
For perspective:
3" ~680-740hp.

 

The diameter of the pipe also effects the speed of the exhaust gases and therefore sound. Higher velocity exiting the tailpipe, or whatever the end of your system is, will tend to sound higher tone. Larger diam and slower speed tends to be lower tone. Note this does not mean volume necessarily.

I generally would default to slightly larger, although I prefer lower rumble. Too big will have detrimental effect on lower end torque though, you need some exhaust velocity to get strong low-end.

 

any more thoughts?

 

Some Corvettes in the seventies used the 2-inch rams horn manifolds but the exhaust pipes stepped up immediately to 2.5. I suspect there is not much loss in the short run of 2-inch.

 

The 2.5" rams cam on the bigger HP small block corvette. Like say 315 and up HP.

The size of your exhaust should be in direct relation to the volume of spent g***es the engine puts out. if you have a small block even a smaller displacement small block that takes a pretty deep breath it will benefit greatly from the larger exhaust manifolds.

Now there is a trick on exhaust (intake as well) that many people don't use or even understand. You can start out smaller and go bigger to increase velocity. On the exhaust side this would be thought of more in scavenging effect. If your exhaust ports dump into a smallish manifold then the manifold dumps into a larger exhaust pipe it becomes very efficient in the way that it scavenges or pulls the spent g***es out. Stepped headers work on this principal.

OK too much info. Stay with the smaller manifolds on a stockish small displacement engine and go with the larger on a well built larger displacement engine.