Which Heads For 540 Sci
11-28-2011, 10:10 AM
#21
[QUOTE=Maxumus;3558059]Good post.....I would like some clarification as well.
I have tested just about every manufacturer's BBC cylinder heads on my flow bench and its my opinion the AFR exhaust ports are more efficient than most, and look especially good in the low and mid-lifts which is perfect for cams most performance boats would consider (with any type of longevity in mind).
I will have to disagree with on the efficienticy of the port. If you look at the valve size vrs. how much the port flows it will tell a different story. 255 cfm @ .600 lift with a 1.880 diameter valve really is not that efficient. Again, 255cfm can be obtained with a smaller diameter valve. Given piston position and pressure at different piston positions/speed. I would give up 5% at .100 and .200 in a heart beat to get it at .600. Remember the piston is slowing down and the valve is opening before it gets to top dead center(overlap). The piston is at full speed (most pressure) half way down the bore. Also where the cam is at max lift.And using a pipe for exhaust flow testing isn't "cheating"....it actually lets you see the true curve of the airflow exiting the port. No different than flowing an intake port with a radius plate helps the air enter the intake properly (a task usually handled by the intake manifold), a pipe helps replicate real word results helping the exhaust gas to exit the port properly.
I have never seen a cheater pipe hurt an exhaust port, in every instance it always helped. It will make a bad port look good or a good port look even better, also it will cover up problems up stream in the port. Good for customer satisfaction It doesn't make the port better or worse....just allows the gas to stay in a column just like it does in just about every engine assuming a header or tubular manifold is bolted to it.
Your right it doesen't make the port better. It "appears" to make the port look better.
I have tested alot of heads with and without flow tubes....some pick up a little and some pick up a lot. At the end of the day I could care less what an exhaust port flows without a pipe....what useful purpose does that serve?
It will throw off the I/E ratio numbers if your a believer in that,(not sure if I'm buying into it), possibly making a wrong decision for exhaust lobe choice. Use the same applicable sized flow tube for all your engine family testing, then cc the port to see how large it is for a quick estimate of CSA comparison, and evaluate all the flow curves. Now you have something real world to chew on and compare notes....with most BBC applications (conventional 24-26' stuff) I use a 2.125 pipe which fits most aftermarket (AFR, Brodix, DART, etc.) as well as OEM head options.
If it works for you thats greatIn the video the cheater pipe helped both ports about 15%
Teague Marine seems like a very fussy shop.....I noticed he uses AFR heads on ALL his high powered (high dollar) boosted builds. I would imagine if there was a better or more cost effective option he would likely use something else, not to mention the countless other shops and individuals I have seen good results from from time to time with AFR product.
Could it be his profit margin is better with the AFR's? I don't know the answer to that question. Im' not saying the heads are bad, I got *****es with the Darts. I'm still pissed they knocked down the floors in the newer Pro One heads.Jim V.....start flowing all your exhaust ports with the same flow tube (you will only need to make about 3-4 different sizes depending on what your testing) and I think you will see things you never saw before concerning the shape of the airflow curve and how different brands now compare when not emptying the port into the atmosphere (which doesn't give the short exhaust port an opportunity to work properly like it would in the real word).
Ever notice how most exhaust ports just kind of die past .500 - .600 lift......test the same port with a representatively sized flow tube and watch not only the numbers change but the shape of the curve change dramatically as well (now the port keeps climbing past the liftpoint it started stalling without the pipe)....and once again some heads respond better than others but assuming the same tube and the same bench is used now you have more meaningful information to chew on.
JMHO
No offenice, but if you have a port that dies at .5 to .6 there's a problem in the porting, most likely in the short turn radius. Small block chevys are notorious for that. If you glue two strings at the flange on an older smll chevy head, one at the roof and one on the floor you will see the string on the roof will flow out and the string on the floor will actually get sucked back in the port, your right, you won't see it with a pipe. Modify the short turn, the problem goes away and it picks up the flow accordingly.
I have tested just about every manufacturer's BBC cylinder heads on my flow bench and its my opinion the AFR exhaust ports are more efficient than most, and look especially good in the low and mid-lifts which is perfect for cams most performance boats would consider (with any type of longevity in mind).
I will have to disagree with on the efficienticy of the port. If you look at the valve size vrs. how much the port flows it will tell a different story. 255 cfm @ .600 lift with a 1.880 diameter valve really is not that efficient. Again, 255cfm can be obtained with a smaller diameter valve. Given piston position and pressure at different piston positions/speed. I would give up 5% at .100 and .200 in a heart beat to get it at .600. Remember the piston is slowing down and the valve is opening before it gets to top dead center(overlap). The piston is at full speed (most pressure) half way down the bore. Also where the cam is at max lift.And using a pipe for exhaust flow testing isn't "cheating"....it actually lets you see the true curve of the airflow exiting the port. No different than flowing an intake port with a radius plate helps the air enter the intake properly (a task usually handled by the intake manifold), a pipe helps replicate real word results helping the exhaust gas to exit the port properly.
I have never seen a cheater pipe hurt an exhaust port, in every instance it always helped. It will make a bad port look good or a good port look even better, also it will cover up problems up stream in the port. Good for customer satisfaction It doesn't make the port better or worse....just allows the gas to stay in a column just like it does in just about every engine assuming a header or tubular manifold is bolted to it.
Your right it doesen't make the port better. It "appears" to make the port look better.
I have tested alot of heads with and without flow tubes....some pick up a little and some pick up a lot. At the end of the day I could care less what an exhaust port flows without a pipe....what useful purpose does that serve?
It will throw off the I/E ratio numbers if your a believer in that,(not sure if I'm buying into it), possibly making a wrong decision for exhaust lobe choice. Use the same applicable sized flow tube for all your engine family testing, then cc the port to see how large it is for a quick estimate of CSA comparison, and evaluate all the flow curves. Now you have something real world to chew on and compare notes....with most BBC applications (conventional 24-26' stuff) I use a 2.125 pipe which fits most aftermarket (AFR, Brodix, DART, etc.) as well as OEM head options.
If it works for you thats greatIn the video the cheater pipe helped both ports about 15%
Teague Marine seems like a very fussy shop.....I noticed he uses AFR heads on ALL his high powered (high dollar) boosted builds. I would imagine if there was a better or more cost effective option he would likely use something else, not to mention the countless other shops and individuals I have seen good results from from time to time with AFR product.
Could it be his profit margin is better with the AFR's? I don't know the answer to that question. Im' not saying the heads are bad, I got *****es with the Darts. I'm still pissed they knocked down the floors in the newer Pro One heads.Jim V.....start flowing all your exhaust ports with the same flow tube (you will only need to make about 3-4 different sizes depending on what your testing) and I think you will see things you never saw before concerning the shape of the airflow curve and how different brands now compare when not emptying the port into the atmosphere (which doesn't give the short exhaust port an opportunity to work properly like it would in the real word).
Ever notice how most exhaust ports just kind of die past .500 - .600 lift......test the same port with a representatively sized flow tube and watch not only the numbers change but the shape of the curve change dramatically as well (now the port keeps climbing past the liftpoint it started stalling without the pipe)....and once again some heads respond better than others but assuming the same tube and the same bench is used now you have more meaningful information to chew on.
JMHO
No offenice, but if you have a port that dies at .5 to .6 there's a problem in the porting, most likely in the short turn radius. Small block chevys are notorious for that. If you glue two strings at the flange on an older smll chevy head, one at the roof and one on the floor you will see the string on the roof will flow out and the string on the floor will actually get sucked back in the port, your right, you won't see it with a pipe. Modify the short turn, the problem goes away and it picks up the flow accordingly.
Last edited by JimV; 11-28-2011 at 02:21 PM.
11-28-2011, 11:06 AM
#22
Haxbyspeed, Maxumus, JimV, interested parties....
All sound like good arguments, and this seems to have been going on for the last several years now---big well known performance head manufacturer with state of the art machinery, engineering & research equipment vs little one man porting shop. Why don't you guys get together and put this argument to rest....at least for a little while.
Correct me if I am wrong, but AFR seems to be saying that their latest and greatest port design cannot be improved upon at least for now without sacrifices in other areas, whereas JimV says he can take AFR's best CNC'd port straight from the AFR factory and improve it with his own porting technique/research.
Why don't ya'll get together and have a well documented, highly publicized flow bench faceoff of some sorts.....maybe even a dyno test to see the actual power differences if any....yeah?
All sound like good arguments, and this seems to have been going on for the last several years now---big well known performance head manufacturer with state of the art machinery, engineering & research equipment vs little one man porting shop. Why don't you guys get together and put this argument to rest....at least for a little while.
Correct me if I am wrong, but AFR seems to be saying that their latest and greatest port design cannot be improved upon at least for now without sacrifices in other areas, whereas JimV says he can take AFR's best CNC'd port straight from the AFR factory and improve it with his own porting technique/research.
Why don't ya'll get together and have a well documented, highly publicized flow bench faceoff of some sorts.....maybe even a dyno test to see the actual power differences if any....yeah?
Last edited by KAAMA; 11-28-2011 at 11:08 AM.
11-28-2011, 12:16 PM
#23
So in summary... As a reputable business man you feel comfortable stating as a fact: All cnc'd AFR heads need their exhaust ports fixed.
If I were a busniess man I would be rich selling product that made me the most money on the sale without doing the investigation on that product to know if that product is what the manifacture claims it is. No, I am saying the AFR big block chevy cnc'd ports do not flow as good as the Dart Pro one ports, ported. I am saying the AFR exhaust ports can be improved (62 cfm @ .700 according to the video).
This conclusion was drawn from testing a head that you believe was a 325, even though the 325 is an "as cast" head, and you think it is probably the current design, and you think all AFR heads share the same exhaust port.
No, Please reread my post. The only conclusion that I drew was what I found flowing the AFR cnc'd exhaust port: step one, out of the box cnc, document, step two, modify the port, document, step three port dart head and compare numbers.
You also like to use the term "cheater pipe". Could you explain the benefit of designing an exhaust port that achieves optimum flow without a pipe attached?
Absolutly. The port starts in the combustion chamber and moves out, the ports are most sensitive around the valve, venturii, and at the bends. In these particular ports the airstream is relatively straight at the flange and pressure is relatively equil. The port has enough lenth and is far enough from the valve to where small changes in the pipe will be minimal. Again reference the video: both the Dart port and the AFR port gained 15% with the cheater pipe Would those magic ports be used on an engine without an exhaust manifold or header? Have you ever seen an engine run without an exhaust manifold or header attached?
Maybe we should start flowing them with a header and exhaust system. Now your talking tuning, not nesessarly airflow. Try this on your port, put an obstruction in the venturii, flow it, put the same obstruction in the pipe. Check results and get back to me with an apoligy
Who cares what a raw port flows, might as well see what it flows without valves in it too.
Funny you brought that up. Did that years ago on a small block ford at Roush's the port flowed more air with the valve in the port than without it. It was an intake port, please don't ask me for the spec's on that one it's been 25 years.
I do not think any of these general statements you have made are facts based on the amount of times you stated "I think", or "I believe". My kid "thinks" the tooth fairy left $2 under his pillow this weekend.. If you're going to make claims please have the facts to back them up, or state that it is "your opinion". That is my opinion..
If I were a busniess man I would be rich selling product that made me the most money on the sale without doing the investigation on that product to know if that product is what the manifacture claims it is. No, I am saying the AFR big block chevy cnc'd ports do not flow as good as the Dart Pro one ports, ported. I am saying the AFR exhaust ports can be improved (62 cfm @ .700 according to the video).
This conclusion was drawn from testing a head that you believe was a 325, even though the 325 is an "as cast" head, and you think it is probably the current design, and you think all AFR heads share the same exhaust port.
No, Please reread my post. The only conclusion that I drew was what I found flowing the AFR cnc'd exhaust port: step one, out of the box cnc, document, step two, modify the port, document, step three port dart head and compare numbers.
You also like to use the term "cheater pipe". Could you explain the benefit of designing an exhaust port that achieves optimum flow without a pipe attached?
Absolutly. The port starts in the combustion chamber and moves out, the ports are most sensitive around the valve, venturii, and at the bends. In these particular ports the airstream is relatively straight at the flange and pressure is relatively equil. The port has enough lenth and is far enough from the valve to where small changes in the pipe will be minimal. Again reference the video: both the Dart port and the AFR port gained 15% with the cheater pipe Would those magic ports be used on an engine without an exhaust manifold or header? Have you ever seen an engine run without an exhaust manifold or header attached?
Maybe we should start flowing them with a header and exhaust system. Now your talking tuning, not nesessarly airflow. Try this on your port, put an obstruction in the venturii, flow it, put the same obstruction in the pipe. Check results and get back to me with an apoligy
Who cares what a raw port flows, might as well see what it flows without valves in it too.
Funny you brought that up. Did that years ago on a small block ford at Roush's the port flowed more air with the valve in the port than without it. It was an intake port, please don't ask me for the spec's on that one it's been 25 years.
I do not think any of these general statements you have made are facts based on the amount of times you stated "I think", or "I believe". My kid "thinks" the tooth fairy left $2 under his pillow this weekend.. If you're going to make claims please have the facts to back them up, or state that it is "your opinion". That is my opinion..
Last edited by JimV; 11-28-2011 at 02:19 PM.
11-28-2011, 12:28 PM
#24
Haxbyspeed, Maxumus, JimV, interested parties....
All sound like good arguments, and this seems to have been going on for the last several years now---big well known performance head manufacturer with state of the art machinery, engineering & research equipment vs little one man porting shop. Why don't you guys get together and put this argument to rest....at least for a little while.
Correct me if I am wrong, but AFR seems to be saying that their latest and greatest port design cannot be improved upon at least for now without sacrifices in other areas, whereas JimV says he can take AFR's best CNC'd port straight from the AFR factory and improve it with his own porting technique/research.
Why don't ya'll get together and have a well documented, highly publicized flow bench faceoff of some sorts.....maybe even a dyno test to see the actual power differences if any....yeah?
All sound like good arguments, and this seems to have been going on for the last several years now---big well known performance head manufacturer with state of the art machinery, engineering & research equipment vs little one man porting shop. Why don't you guys get together and put this argument to rest....at least for a little while.
Correct me if I am wrong, but AFR seems to be saying that their latest and greatest port design cannot be improved upon at least for now without sacrifices in other areas, whereas JimV says he can take AFR's best CNC'd port straight from the AFR factory and improve it with his own porting technique/research.
Why don't ya'll get together and have a well documented, highly publicized flow bench faceoff of some sorts.....maybe even a dyno test to see the actual power differences if any....yeah?
I'm waiting on the plane ticket
11-28-2011, 12:46 PM
#25
Registered
Platinum MemberJoin Date: Mar 2008
Location: Vancouver BC
Posts: 1,181
Likes: 0
Received 0 Likes
on
0 Posts
I am sorry someone blew enough smoke your azz that you believed it.
I am saying the AFR big block chevy cnc'd ports do not flow as good as the Dart Pro one ports, ported.
No, Please reread my post. The only conclusion that I drew was what I found flowing the AFR cnc'd exhaust port: step one, out of the box cnc, document, step two, modify the port, document, step three port dart head and compare numbers.
I am saying the AFR big block chevy cnc'd ports do not flow as good as the Dart Pro one ports, ported.
No, Please reread my post. The only conclusion that I drew was what I found flowing the AFR cnc'd exhaust port: step one, out of the box cnc, document, step two, modify the port, document, step three port dart head and compare numbers.
11-28-2011, 12:55 PM
#26
Yes, but what's happening is the pipe is covering up a flaw in the head. If you were to fix the turbulance in the head first, the airflow will be there or close to it.. Adding the pipe will make it flow even more air. It's tough to improve on a port that is already to big, plus those valve angles make it worse.
11-28-2011, 01:16 PM
#27
I think that is a little different then what you were first claiming.. Also, are you stating that the well used AFR head with peeling paint and corrosion is "out of the box"? Is it possible that the valve job could have been done at some point and caused a flow problem? Anyway, my point is your "tests" are anything but scientific or valid. Good luck, Alex.
I have had at least 10 sets of those heads in my shop all results are the same, new or used. The ports simply don't have enough volume to justify the valve size. I can't see how chipped paint on the outside of the head has anything to do with it. The ports are clean.
11-28-2011, 01:34 PM
#28
Geronimo36
Gold Member
So what would be the best out-of-the box head to run on a 580 cubic inch blower motor currently making 838 hp and 832 ft. lbs of torque?
Engines are 580 cu. in., Merlin Iron 345CC with 119cc chambers, 8.3:1 compression ratio, blown with 7 lbs boost. Max Tq is @ 4500 (834 tq) and max HP is @ 5800 (838). Cam is a solid roller; 254/262 @ 50, 304/312 advertised duration, .636 lift but on a 112.
I'm not looking to make more peak power as much as I'm looking to improve safety/detonation, maintain mid-range and and reduce boat weight.
Engines are 580 cu. in., Merlin Iron 345CC with 119cc chambers, 8.3:1 compression ratio, blown with 7 lbs boost. Max Tq is @ 4500 (834 tq) and max HP is @ 5800 (838). Cam is a solid roller; 254/262 @ 50, 304/312 advertised duration, .636 lift but on a 112.
I'm not looking to make more peak power as much as I'm looking to improve safety/detonation, maintain mid-range and and reduce boat weight.
11-28-2011, 05:37 PM
#29
Of these heads, all Dart Pro 1's - 325 CC, 335 CNC or 345 CC would you use on a 540 SCI running a max 5500 RPM. 871 blower EFI. Cam is 248/256 duration .637 lift. I'm getting mixed reports, one say use 325CC to keep flow velocity up, others say go with 345 cc for more air. Many say 335 CNC ported because they move the most air. Cruise performance is most important with an occasional run to 5500 RPM. Again heads are Dart because i have access to these three styles. Thanks,
11-28-2011, 08:56 PM
#30
Registered
Platinum MemberThread Starter
iTrader: (3)
Join Date: Jan 2010
Location: North Bend Ohio
Posts: 297
Likes: 0
Received 0 Likes
on
0 Posts
Called Bob last week. He is working on a cam profile as soon as i get flow numbers. 325 CC's are going to Michigan to Total Flow. He has a very good CNC profile for 325's that will get me as good or better than the 335 CNC Dart Pro 1's. Talked to AFR also. They to were helpful. Off the record said port what i have since a good program has been done on the 325's.
