GT40 intake VS Edelbrock 5.0 performer

ninety15.0 is correct, there is some math, but there are many other considerations. The inner radius around bends can not be too steep or the flow will separate causing reductions in flow, the diameter should be chosen correctly to maintain the correct port velocity for the engine speed and displacement characteristics, and attention should be paid to the transitions at any adjoining surfaces as these also cause flow separation. Fluid dynamics only goes so far, as an IC engine is an Nth order polynomial. The intake is an open and closed reed system with a throttling valve and usually one accumulator chamber. The flow driving mechanism is a dynamic system involving temperature, changing velocity & pressure, as well as what is called the "Gulp Factor." These factors are why people with a lot of porting experience, trial and error research, and lots and lots of flow testing are more effective than using math to model an intake design.

Walls

Exactly Walls...Calculus/mathematical modeling will only take you so far. If I have learned anything as an Engineer its that you learn to deal with error. what I mean by that is theoretical formulae will only get you so close...and correction factors are tacked onto every calculation I make. Closed form equations are easier..and get you as close as you need to be most of the time. With cylinder heads...testing is what takes you from theoretical calculations to actual peak flow values.

You could spend hours calculating Theoretical Max radii, port dimensions, runner length to satisfy a particular engine combination. And that will just give you a place to start...from there you must fine tune and test....and then retest. Again i guarantee that head porters dont sit down and calculate non-linear differential equations to describe fluid compressibility/viscosity....mach and reynolds numbers? (yikes i hate saying chit like that) The fluid dynamics inside a cylinder head are no easy model. Think about how cylinder heads are tested? I dont know a whole lot about test flow benches but i would assume that they use constant flow rates (maybe more than one test point) and constant vacuum? So this means they are testing a static scenario. Now how do you model fluid flow when you toss a valve in that port...one that opens and closes rapidly? And then an intake manifold...then a throttle body and exhaust headers...see what i mean?!

Just some food for thought...i think this is a interesting topic. Tmoss share you opinions on how much mathematical modeling you do?!

if you go to the sites where the head porters live, you'll find they spend an immense amount of time testing velocity and velocity profiles through the inlet side. Yes, they know what port sizes and run ner lengths are good starting points but they always get refined.

hate to thread jack but ive got several questions about my gt40 motor if anyone is still on the subject???

well since you woke everyone up you may as well ask. sheesh.

Someone has a edelbrock rpm performer in a big city over from me (200 miles in texas lol) for a good deal i think, $250. I might have to go grab it this weekend. My car has a e cam, and ill throw on some gt40 3 bar heads when i do the intake. Will upgrade springs and valves. Should i run 1.7 or 1.6 rocker w/ that? I want 1.7's based on some quick research. Not a biggie either way sounds like, other than 1.7's might not clear valve covers w/o removing baffle.