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Good info. Volumetric efficiency is very important to make power. Usually your street rod motors are only in the 80s and maybe 90s if they got it hyped up. A good all out race engine can start in the upper 90s and go in the 110-115 range. Usually takes a pretty big cam 260+ @ .050 a lot of cr 12:1+, good flowing heads 280+ ect to achieve anything over 100. Who also has good info on this is Rehere Morrison Championship Engine Assembly.




Very true, but we're mixing the pews in the church.
High compression ratios's are not necessarily required for high VE. Also, large duration profiles are not the answer either.

Here's an example:

350 cu in engine Cam in the 260 - 270 deg @ 0.050"
Decent flowing head 10:1 static comp
VE at 6000 rpm < VE at 8000 rpm.

Why?



IVC happens ABDC.

Using the general rule of thumb that peak VE occurs at peak torque (again, in general), I'm curious to know how your example engine could be less VE @ 6k than 8k. Cylinder filling tapers off after peak torque...where max filling occurs...

Some have touched on what I've seen...big efficient ports, low overlap...the intake ports don't need the exhausts help. The advantage to this is greater driveability if a street/strip car...which is what I'm mostly familiar w/.

Don't expect to run an off the shelf cam on a head w/ what are thought of as 'big ports'. Conventional thinking...70s/80s ideas of what cam to use...will lead to the torqueless engines people are warning about.

Last edited by Cogito; 01/14/15 03:31 AM.