Edelbrock heads vs Indy

The AMC dog leg can be made to flow astonishingly well. It is quite a bit larger than the Edelbrock in csa although both have quite a variation through the port length. If you port the iron head right (and it is simple but not necessarily intuitive) you can keep the flow attached to the SSR and get truly astonishing flow numbers. The phenomena is a fairly advanced aerodynamic trick that I'll bet the AMC engineers had no clue about 50 years ago. Blind luck is great. The Edelbrock cannot get even remotely close. For that matter an iron can outflow an Indy. When you get a bunch of various heads across the bench over the years you get to realize just how good the dog leg is flow wise.

However, one thing to remember is flow bench conditions are unrelated to a running engine. In the blowdown phase the exhaust flow is sonic, and the temp is in the 1400 F range. Name a flowbench that can do that. Many (me included) consider a flowbench fairly useless for developing exhaust. I do not care what the flow is. I do care what the port size and shape is.

So is the amazingly good dog leg exhaust port flow (with the right porting) a good thing? Does the fact that you can keep the flow attached to the SSR at flowbench conditions matter?

I don't know.

So here's my question... Take a running and driving mild performance build with untouched iron heads and replace with Edelbrock out of the box heads (for sake of argument, cc's are the same and compression remains the same). What kind of performance difference will be felt? Noticeable? Little? I understand the weight savings of alum and ability to build for higher CR with same octane fuel is also part of the reason to go with aluminum heads- just trying to compare apples to apples.

Interesting discussion. KingsX, I am very pleased with my setup and the Edelbrock heads work just fine. The largest problem that I have is getting traction. You will have none on the streets guaranteed regardless of which head you choose. So, unless you are trying to be as comptetive as possible the Eddy heads are a great bolt on that require little to no work. If you were near me I would take you for a spin and let you see for yourself. The thing is quite extreme and scares me everytime I stomp the long skinny pedal.

Interesting that all out drag race high compression high speed stuff has gone for smaller and smaller exhaust valves and ports. Apparently that technology is considered too small for Nascar - exhaust system maybe? And newer factory stuff seems to have fairly small exhaust ports.

But what is also interesting is I do not see more recent race designs that are closer to stock port locations using the perhaps inadvertent AMC Aerodynamic trick. I've never seen ANYTHING with a factory type port location touch what an AMC exhaust can flow, and I've had a lot of stuff across the bench.

I will say that the upside for Kings application and selecting an aluminum head is going to be the additional heat dispersion inherrent in aluminum heads. Since he is running on the street and running boost, that is one thing that makes them worth buying. I also don't think the guy who spends 4-6k on a supoercharger is going to be too concerned with spending 2k on a set of aluminum heads especially if it means he has better detonation resistance which in a supercharged vehicle I will take every fractional bit of help I can to avoid.