Very informative thread, Thx Eddie
It is this interaction with everyone and his honesty that put me on his door step last winter. I am thrilled with my 572's with aluminum heads from Eddie.
Very informative thread, Thx Eddie
Very nice job of providing numbers from your work and great comparisons of cfm flows at various lifts.
Question? Do you have a velocity probe on your flow bench?
When we worked with Darrin Morgan and developed our Raylar 496 BigPower aluminum heads we found that looking at flow numbers was important , but not the whole story. We found out that port velocity of the air flow was also of major importance.
It also seems to sometimes hold true that some supposedly smaller air flow heads make more power on the dyno or in the boat. I suspicion the reason is air flow balanced with good port velocities as well as some air charge direction into the combustion chamber and tumble, things we had to learn before we could really get an exceptional head and make good marine performance power.
As a good comparison on our standard Stage 1 Raylar head we have only a 318CC intake port and just a 2.20" intake valve and yet at .600 lift we develope 365 cfm.
How did that happen - VELOCITY OF THE AIR! This is also a very important factor as you already know in developing low and midrange power and torque which are very important as we all know in performance boating.
I guess what I am leaning towards here is the fact that bigger flow numbers are not always the real answer or final point for selection of a good marine performance head, especially on normally aspirated engines.
We also with this air velocity measurements at various places in the intake and exhaust port found out amazing things, like on the exit floor of most BBC ports the area about 1/8" to 3/16" up off of the floor had almost NO AIR FLOWING! while the rest of the port was screaming! Good reason for straightened-raised exhaust ports. the bends and negative sections in ports really help destroy flow and velocity.
Just some info here, do not want to hijack your work and post! I really appreciate it when knowledgeable people and shops like yourself share their knowledge and expertise.
Eddie, it would be nice to make these velocity measurements and compare the differences between these heads you are comparing and I think from what we've seen its pretty easy to rig a simple velocity probe on your flow bench. If you have a SuperFlow, I think they can get you setup for that probe. Might show some interesting info that will help in head selection.
Hope Raylar's head development work can help all our fellow OSO'ers in their head changes and modifications.
Ray @ Raylar
Last edited by Raylar; 01-18-2010 at 12:11 PM.
Thanks for the info Ray. At the time, I did not have a velocity probe. I am working on it now and will have it set up the next time. All of these heads were going on SC engines so I wasn't that concerned about losing much velocity. The other thing is that you would be surprised at how little I did. They actually did not require much.
The Brodix heads had a few holidays where the cnc bit did not even cut, especially around the guides. They also did not meet up where they cut from both sides. On both the Brodix and the AFR's there is over 1/16" step where the cutters met in the middle. They both also left a sharp turn on the short side radius of the exhaust port. This is where I did the majority of the work.
I didn't have to do the Brodix heads. I could have used them like they were and made the power that I was after. I sold the customer a complete package, so I essentially did the heads for free. I did not get any extra money for doing it. I just saw an opportunity to try a few things to see if I could improve it.
What about aftermarket iron heads vs. the aluminum you selected? Such as Grumpy Jenkins and Iron Eagles vs. the others?
I rarely use cast iron heads. I'm sure there are several good flowing heads out there. I usually stick to the alum. for the head dissipation qualities.
I would love to flow a set to see what they do. I don't really count on published numbers because they are all trying to make their heads look better than the others. That is why I did this. I wanted a direct comparison without the variables of different flow benches, different operators, with or without a pipe, etc.
I am not trying to sell port work. I absolutely despise porting heads and if I never have to do another set, then that will be fine with me. You can never get enough money for the time it takes. I wanted to see if they could be improved on and how they compare with each other.
I will definitely do more in the future. I will be glad to post the results. Thanks.
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