I am working on some testing using some big block heads. The castings I am using is a 906. I am using a SuperFlow 600, and 25" H2O. I started out with a stock flow of about 172 IN and 142 EX. Modifications I have done, testing after each one include 3 angle grind, 5 angle Serdi grind, polished the chamber and blended the seat area, then worked on the bowl and short side radius using the porting tempates. I then flowed it with backcut valves After all of that I was expecting a decent amount of CFM. The final Numbers were 181.5 IN and 156.5 EX. I did pick some low lift flow numbers. I would like to achieve arounnd 230 CFM of flow to achieve 500 Horse. What am I doing wrong, Let me know if you need any more info and or numbers. Thanks!

a couple of things...First, it seems most of the porters here test at lower vaccum, but convert the findings to 28" specs...This may be while you're a little lower than what is read here. Second, what type of valves are you testing? For lower lift flow, you should be using nail head performance style, not the stock tulip type. Also, many times when you do work in the bowls, the guide area and pushrod pinch should also be touched a little, otherwise it's a choke point. You may want to post in the race forum..See if Curtis or Dwayne can shed light here.

its really difficult to try and compare flow from one bench to another.

basically, you need to test somekind of heads thats a known quantity on that bench to get a baseline.

the 172 you're getting from the stock intake port would only be 182 @ 28", which is still way below(by about 30cfm) the norm.

what size bore adapter are you testing on?

what are you using for a port entry radius?

go to mopar muscles's website. there's a 3 or 5 part series on BB head flow done by steve dulcich, with a lot of good info. IIRC, he achied close to 230cfm of flow using the MP porting templates.

What lift were those flow numbers achieved at? Have you checked to be sure you operated and read the bench correctly? Have you tested more than one set of ports?

I believe that the main problems I had with the flow numbers is that th bore adapter i use is actually somewhat small. The valves open completley, but I feel there is some shrouding going on. Another concern is getting the head exactly centered. I am not using dowels t oensure exact location. I am sure of the bench calibration. I am using a 600 with Flow Com. So basically you cant mess it up there. My leakages werent real bad (about 2CFM) I read the article on Mopar Muscles site. It is good and very helpful. I perfomed a back cut on the valve and really picked up some flow, with a minor mod like that. I am going to finish my bowl work and possibly enlarge the valves, the build my own adapter and do some more testing. Thanks for all your help.

Also I have heard some conflicting info on the short side radius of these heads. Should you leave it alone or smooth its transition out? What about snad blasting an intake port after your port work? I have been told this gets the right texture for a good atomization. Is this true? Thanks

i'd test on a 4.250 bore minimum.
if you use that size, its best to shift the head so the side of the chamber your testing(intake valve or exhaust valve)is adjacent to the wall of the bore adapter.

you didnt say whether or not you were using a radiused port entry. this is a must.

if you're looking for "the big number", intake short turn work is absolutely mandatory.

its a "make or break" part of the job.
done correctly the head will come alive at high lifts....done incorrectly, the port will die at .450-.500 lift(on a 906 head).

I am not using a inlet radius. Will this affect numbers much? Also what should I avoid on the short side radius? Also will I see any major gains using the larger valves? I do not have hardened seats either, should I use these? The engine will not be drove a whole lot, just on weekends and some nice day drives Thanks

Without a radiused entry to the port the air with not enter smoothly and it will break up. You can tell the difference in sound with and without a radius.My bench is home made.I've had very little time to mess with it since I got it built due to work but I got today off and I think I'll fool around with it.I've been trying to figure out a good baseline in which to test my heads.I think what I'm going to do is drill a nice size hole for an orifice plate. One that I know will flow a good bit more than a stock 906 intake port but not way more than.Then I'm going to just figure that the port flows about 210cfm at .500 lift. This may be a bit conservative but I would rather be conservative than to think my heads are going to flow like B1's. From there I'm going to read the percentage scale and whatever it reads I will assume that to be 210 cfm of whatever the orifice plate is. Then I'll be able to exact a figure for the maximum cfm for the orifice plate.I'll do all this at 28 inches of water.

I would also like to add something about the orifice plates. Once I give one plate a cfm figure I should be able to guage other orifice sizes by flowing them against it.That way I can flow ports to the nearest sized orifice plate that flows slightly higher than the port.That way I can get closer to 100% and be more accurate than if I used an orifice plate that outflows the port considerably higher.

I have done much research and testing on the flowbench. Have you ever tested a newer style stock production head? I have flowed many without an inlet radius, and I have also flowed them with them on. I know that when comparing numbers to other benches, a radius inlet must be used. I also understand that the guid e can allow for much more CFM. I would like to see what I get without the radius and then compare it with the guide, and see how much CFM it makes a difference of. Also flowing on 28" compared to 25". I know there is CFM here as well. Thanks

You MUST use some sort of radiused entry!!!! You see if the air goes turbuelent as it enters the port, then any data collected is no good! It must enter the port smoothly, and yes the numbers will go up becuase the turbulence is gone. This is a must, not to get false high numbers but to get CORRECT numbers! I use clay, and stick to a shape on every head so that helps to keep all tests evenly comparable.
Brian

IMO, if you're not using a radius entry, the numbers are meaningless.

the jist of your original post is, why are the numbers on your 906 head so low?
the answer is the test procedure is being done incorrectly.

For before and after comparison I do not think that the radius inlet is needed. However yes, my post asks why it is low compared to other findings. In that case I do feel that is essential for bench to bench data comparison. So I can see your point. Thanks a lot guys.

I agree with Fast68. A radius inlet will affect some ports more than others due to various factors, but one point is the better the port flows for the cross section, the more likely tests will show it with a radiused entry incorporated. In other words, a radius inlet will allow you to acurately see any actual improvements. That's because as the velocity gets higher (more flow for a given cross section), the turbulence gets more pronounced at the sharp inlet. When a port is kind of “lazy”, the velocity along the port walls can be pretty low. But as the flow increases, much of the additional flow will be closer to the port walls.

Most successful porting increases the flow while keeping the cross section increase minimal.