sure you could have 3psi of pressure on the back side of the intake valve,, depends on the combo, rpm range, really just about everything that has to do with the engine. really when you get to looking at a depression, and trying to effectively filling a cylinder,, it takes a free or good flowing head which is usually larger in cross section therefore you need to try to evenly pull on the port with how the piston comes off tdc. alot of guys think the rod connects the crank to the piston, but it will dictate the rate of accleration the piston will decend till the mid point of the cylinder, which is the same for any rod. usually this is a rod ratio of 1.65-1.7, dependning on the storke respective to the port cross section again, that can be changed to help an rpm range thats desired to run, or able to be run, we all want to run it as high as you can without the valve train blowing up.

another thought with sheet metal manifolds,,, its common knowledge that you should contain your swept volume at whatever efficiency your engine will run at,, i usually say 115%,,, in the runner so that your complete mixture that will end up in the cylinder has the initial inertia of being in the runner when the valve first opens to get maximum pressure effecting on the cylinder. by working on volumes in manifolds like that its crazy how much power you can gain,, for every degree of intake valve timing that i can hold it open longer ill get about 7hp. but for an engine like a pro stock, its closer to 12hp,, when you consider how much piston movement 1 degree is you understand how tempermental the pressures are and how a little bit,, can be a whole lot.

did i run on??,, i had a late night


jeff