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Valve & Guide Test - Budget Flow Bench (Read 212 times)
DragBikeMike
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Re: Valve & Guide Test - Budget Flow Bench
Reply #45 - 01/26/19 at 19:27:02
 
1/26/19 Update
I had the good fortune of getting a test mule cylinder head from Fast650.  His generous gift will allow us to learn a lot more about how the budget flow bench works and also to do some preliminary work on the ports prior to removing metal from a good head.  I call the test mule “The Hammer Head”.  As you can see, the name is appropriate.
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DragBikeMike
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Re: Valve & Guide Test - Budget Flow Bench
Reply #46 - 01/26/19 at 19:28:27
 
With a little epoxy and some work with a die grinder the old girl cleaned up fairly well.  She’ll never run again but she’s good enough to use as a test mule.
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Re: Valve & Guide Test - Budget Flow Bench
Reply #47 - 01/26/19 at 19:31:22
 
I wanted to test the Hammer Head and compare the results to my good used head which I will refer to as my “Performance Head”.  If the baseline results are close, then the mule will be a valid tool to show how various modifications work.  Here’s how the mule looked set up on the flow bench for intake port testing.  Note that the exhaust port is sealed off to eliminate any concern over leaking valves.
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Re: Valve & Guide Test - Budget Flow Bench
Reply #48 - 01/26/19 at 19:32:25
 
I made a decent jack to position the valves and an air horn to smooth out the airflow.
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Re: Valve & Guide Test - Budget Flow Bench
Reply #49 - 01/26/19 at 19:33:53
 
For exhaust tests, I fabricated a fitting that matches the geometry of the stock header pipe and gasket.
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Re: Valve & Guide Test - Budget Flow Bench
Reply #50 - 01/26/19 at 19:34:57
 
I wanted to blow through the cylinder head for the exhaust tests so I fabricated a bleed valve chamber from some 4” ABS.
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Re: Valve & Guide Test - Budget Flow Bench
Reply #51 - 01/26/19 at 19:39:28
 
I decided that I would use 10” H2O as my test pressure for all tests.  The rig isn’t robust enough to pull big numbers so 10” seemed like a happy medium.  The plan is to pull the highest pressure I can achieve and then convert to 10” using the DTec conversion tables.  If I can’t pull at least 10”, I will pull what I can achieve and then convert to 10”.  That way, all final results will be expressed at 10” H2O.  

After hours of testing at varying test pressures, I confirmed that I get essentially the same results when I convert to 10”.  For instance, when I test an item at 15” and get 84 CFM, and then test the same item at 6” and get 53 CFM, and I use the conversion tables to convert both results to 10” I end up with 68 CFM @ 10” H2O.  Science, it works every time.

My intent is to check flow at .025” increments to allow matching head modifications to particular camshafts, the idea being that cams that open the valves quickly but have relatively low lift will benefit more from mods that improve flow at the lower lifts.  In addition, the currently available cams lift the valves in the range of .018” to .083” during the overlap period, so having test data in small increments at the low lift positions seems beneficial.

I started with the intake port.  Opening both valves, it was apparent that I would not be able to maintain at least 10” H2O over a complete valve cycle.  I decided to use declining test pressures from low lift to high lift, similar to a floating pressure drop test.  However, I didn’t just allow the test pressure to float, I lowered the pressure using the bleed valves to allow testing at a predetermined pressure for various lift positions.  That way, I would always be testing at the same pressures.  For instance, at low lifts I used 15” H2O test pressure, and will continue to use 15” at low lifts to evaluate mods.  As the lifts increased, I had to use lower test pressures, and will continue to use those exact test pressures at each valve position to evaluate mods.

Opening a single valve, I was able to maintain 15” H2O through a complete valve cycle from .025” through .400” lift.  I decided to test the individual port runners using a fixed test pressure of 15” H2O.

On the intake port, the flow bench performed very well.  It was consistent throughout the testing.  I could walk away from the project for several hours or even overnight and get exactly the same results when I did cross checks later on.
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Re: Valve & Guide Test - Budget Flow Bench
Reply #52 - 01/26/19 at 19:44:40
 
The following graphs provide the results of the baseline testing on the intake port.  An anomaly was noted during the single runner tests on the right runner at the .300” lift point.  Flow decreased significantly from .275” to .300” lift.   Test pressure was consistent.  I repeated the test three times over two-days.  The results were always exactly the same.  The anomaly was noted on both cylinder heads.  I conclude that the converging flows tend to straighten each other out but when only one runner is flowing the turbulence created at the convergence point upsets flow at the .300” through .400” lift points.
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Re: Valve & Guide Test - Budget Flow Bench
Reply #53 - 01/26/19 at 19:45:47
 
Here's the intake data on the good head.  Pretty close.
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Re: Valve & Guide Test - Budget Flow Bench
Reply #54 - 01/26/19 at 19:48:19
 
I switched to the blow through setup for the exhaust port.  I blanked the intake port to eliminate any concern over leaking valves.  It didn’t take long for me to figure out that my sketch for the blow through setup was wrong.  I had the U-Tube hooked up to the wrong side of the orifice.  It belongs between the orifice and the combustion chamber.  I fixed that and also corrected the sketch in this post.
 
On the exhaust port, I was only able to achieve 6” H2O with the blow through setup.  I suspect that a good portion of the air flow is directed over the motor for cooling, which greatly reduces the volume available for the blow through test.  The data was clean and consistent, but the pressure was so low that I wasn’t happy.  I decided to try and suck through the exhaust and then compare the data to the blow through results.  I set up a suck through rig.
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Re: Valve & Guide Test - Budget Flow Bench
Reply #55 - 01/26/19 at 19:49:52
 
Here is an illustration of how the suck through setup is configured.
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Re: Valve & Guide Test - Budget Flow Bench
Reply #56 - 01/26/19 at 19:53:03
 
With the suck through rig I was able to pull 15” for all the exhaust port testing.  When I compared the suck through flow data converted to 10” H2O to the blow through data converted to 10” H2O, the results were very close, with the suck through flow being slightly lower by just a few CFM.  I felt that was reasonable because the resistance increases as the test pressure is increased.  Things looked good.  The following graphs provide the flow data on the exhaust port.
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Re: Valve & Guide Test - Budget Flow Bench
Reply #57 - 01/26/19 at 19:53:50
 
Here's the graph on the good head.  Pretty close again.
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Re: Valve & Guide Test - Budget Flow Bench
Reply #58 - 01/26/19 at 19:56:05
 
So I think we have some good baseline data to use as we move forward.  The Hammer Head flowed 146 CFM on the intake and 94 CFM on the exhaust with a flow bias of 64.3%.  The Performance Head flowed 150 CFM on the intake and 93 CFM on the exhaust with a flow bias of 62.0%.  I think that’s close enough to show that we have a good test mule.  The data has been measured in .025” lift increments so we can look at modifications that might possibly improve the low lift flow without killing velocity.

As I try various modification, I will test them and post the results here.  I will try to group the mods in categories. For instance, simple low-impact mods that don’t risk damage to the head like cleaning up dingle berries or blending seats to the port wall, mods that involve replaceable parts like cutting back valve guides or back-cutting valves, mods that involve filling in stud holes or the dipsy-doodle in the exhaust port, and last, mods that risk the head like installing larger valves and opening up ports.

A BIG shout out to Fast650 for donating the Hammer Head for this project.  I hope I’m up to the job.

Best regards, Mike
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