Panther, I have asked JimV this. He says the Dart Iron Eagles flow the same as the Pro1.

Nice Read !

I don't know if it has already been said. With Aluminum heads if you are going to have serious $ into them at least if they are damaged to some extent they can be welded up and remachined like new.
I am running PRO 1's that were highly worked by Jim V.

Will the real Good BBC head please stand UP!
 

Eddie:

Great to hear you may be able to measure some port velocities, it will be interesting to see what you find. We have been working on a CNC and rework program for the Mercury Racing (Edelbrock) produced head that is used on the HP525EFI's and some of Mercury Racings supercharged offerings.
One thing that really seems to hurt the performance of a lot of big block chevy aluminum and iron heads both is that their seems to be this idea within a lot of standard BBC head manufacturers that they have to stay with the old GM port shapes, bowl designs and combustion chamber shapes. Obviously Brodix , Dart, Profiler and some others have designed their own high port aftermarket heads and some spreadport raised spreadport designs that will really make big flow numbers and big horspower numbers on many higher rpm race engines, blower engines, etc. But when it comes to the standard BBC marine performance normally aspirated, fuel injected or carburated engine that fills the vast majority of most performance boaters engine bays, the architecture, design and execution of these heads tends to be almost antique in terms of what really could be with a good GEN 4,5 or 6 engine head.
When we measured the flow numbers of the Mercury Racing head for example, which was basically brought to market in 2001, we found the numbers for flow anemic, of very low velocity and the combustion chamber dates back to 1967! It seems that with many of these stock replacement aluminum and iron heads that the efficency of port size, shape, bowl design, and such is so lacking that the only way that many engine builders, head shops and and users can make bigger power with these heads is to open the ports to overly big port cc numbers with bigger valves and demonstrate just big CFM numbers from a flow bench that really does not even pull on the incoming air charge like the real engine does and stick domes in the combustion chamber to push compression ratios up for more power.
I don't know the anywhere near all the answers but I do know in some cases just port shape redesign, raising port elevations, recontouring bowls and combustion chambers, which in some cases may make the port and valve diameters smaller, could really make better power and torque for marine usage than some of these aftermarket offerings.
Again, I guess it always comes back to that old addage, that an engine is nothing more than an air pump and as such the real secret of power is an intake, combustion and exhaust design that packs the most air and fuel in the cylinder prior to ignition and gets the most exhaust out the quickest after combustion.

We have discovered thru our narrow GEN 4,5 & 6 BBC head research and development that a better modified aluminum head that fits up to current marine intake and exhaust configurations is really possible, but it actually may require adding material (aluminum ) to the head and not taking it away with porting. Bigger is not always Better. Interesting thought here and the results might surprise many. I wish more of the existing BBC aluminum head manufacturers would take this approach and offer a significantly re-designed head that would fit the older engines and use the newer head performance technology instead of just passing off old designs for major bucks!

Well, just some more of my crazy head design ramblings, I wish we had more capital and time to develop such a head, the market could really use them.
In the mean time at least we will have a modified Mercury head that makes our new HP525EFI to the Raylar HO675 engine exchange program work. Oh Ya and a new modified intake to also make it work. Ya, we been busy!
After developing and manufacturing our own cylinder head for the 496, I can tell you its an expensive, time consuming and sometimes frustrating endeavor. Definitly not for the faint of heart or Wallet!

Eddie, keep up the great work and investigations, nothing ever gets better without the effort!

Best Regards,
Ray @ Raylar

It's about time you put the college degree to work. :eek:
As allways thanks for your free time and effort!! :D
Explain whats a head again. :lolhit:

Ray - Jim V puts wedjes in some of his heads to raise the floor of the intake and increase the port velocity.

It's the purple bulbous thing at the end of the shaft:lolhit:

Thanks Keith. Talk to ya soon.

Ray,
I absolutely see where you are coming from. I am certainly no expert and don't have the answers, but I think there are plenty of places for improvement. I believe everyone's problem is time and capital. They are building heads that people are buying, so why mess with it. It's a crap shoot because people are afraid of what they no nothing about.
Now, correct me if I'm wrong. GM came out with the cathedral port in the LS engines. Now, they have gone back to the rectangle port because they are making more power. Why it that?
Eddie

Thanks Eddie. I was curious of the flow numbers and comparision with the Iron aftermarket heards vs. the more expensive and technologically advanced Alum. aftermarket heads since the aftermarket Iron's are supposed to provide increased flow and power over the stock GM's. :)

No comparison on the advantage of the aluminum heads and wish I had the cash to splash!!! Maybe that'll change in 2010!:coolcowboy:

I just finished refreshing one of my 800's and replaced my old Merlin Iron 345's with a new set of Grumpy Merlin Iron 345's and the biggest upgrade I noticed is they switched from 3/8 valves to 11/32'nds

Hello Again Eddie and Tinkerer:

Yes you are correct. Putting material back on the floor of the intake port in most standard BBC rectangle port heads and making a nice shortside radius into the intake valve actually improves flow in these heads with velocity and a more gradual angle change for the incoming air charge. When you lookat wet flow tests on most standard rectangle port BBC heads you see the air/fuel charge go down the port, hit the backwall of the bowl, riccochet back against the back portion of the intake valve and then weasel its way into the chamber! Kinda like a billiard ball on a pool table! Not very efficient or good for flow or velocity. Obviously air movements and especially air flow in ports or heads is a bit of a black art, but the newer measurement and observation methods are sorting out the problems.
Air does not like to turn corners and every turn, loop, twist and change in direction results in lesser air flow. This is why when you see many new racing head designs in high end race engines you can usually look right down the port and see the entire valve seat area or most of it.
The current majority of BBC heads on the market today are old 1965-1970 port and combustion chamber designs and they are incredibly inefficient.
Well enough of this technical gobblygook!

Yes Eddie, on the original LS1 design heads GM was trying to make a symetrical port flow more efficiently at low lift flow ranges with smaller emmisions type reasons. At the same time they developed the LS7 head and port design for the C5R program and realized it was a much better design, so now GM has switched the LS heads back to a highly raised rectangular entrance high velocity tapered port design that you see now in the later LS3 and L92 design heads. High ports with straighter angles, thats the biggest part of the equation.

Best Regards,
Ray @ Raylar

Panther,
Here are some flow numbers on our JimV reworked Dart IE. The intake ports were 323 cc. Note that the AFR 315 CNC numbers are noted at the bottom (from the AFR website). All the flow work was independently tested in TX. As you can see, the intake flow is very similar the the AFR and JimV exhaust ports are killer. These heads made 800+HP NA with 503 CI. Cast iron can make the same power at a similar cost to aluminum.
Whats the real difference? Cast iron last longer but aluminum is lighter :angry-smiley-038: