Sorry about the picture of the inclined manometer.  For some reason it got rotated 90 degrees and I don't know how to rotate it back.

Here's a closer look at the scale.

I found that the snubber valve was pretty much useless.  I think you can leave it out.  The incline is 14” long and set to 30 degrees.   You need the syringe body to act as a reservoir.  The water column moves down and to the right as the flow increases.  This results in the syringe filling with water.  The distance between the graduations is critical but the spread sheet makes it very easy to mark off the scale.  Its not linear, so you must use the spread sheet data, but it really is simply plug & play.   The action is smoother and resolution greater than the u-tube.  

The u-tube is just a yardstick with nylon tubing wired to it.

Ooops! Another auto-rotate.

Normally the contraption would sit upright with the base of the cylinder head situated on top. There's a picture of that configuration in one of the earlier entries.  The head will be sealed with a foam gasket and I will utilize an appropriate plastic cylinder sized to simulate the actual cylinder that the head is intended to be used on (94mm, 95mm or 97mm).  The cylinder insert will be fabricated from a 3” x 4” ABS bushing inserted into the closet flange.

Operation is simple.

-Zero out the inclined manometer by raising or lowering the syringe body.

-Zero out the u-tube manometer by adjusting fluid level.

-Select and install a trial orifice that you think will be close.

-Assemble the rig and mount the test specimen.

-If you are testing a cylinder head, set the valve to the desired position.

-Make sure all the bleeds are full open.

-Fire up the vacuum cleaner and start closing the bleed valve/s until you reach the desired test pressure on the u-tube.  Remember, the reading is the difference between the two columns.  If the left side moves down 3”, and the right side moves up 3”, the reading on the u-tube is 6” H2O.  If you are testing at 15” H2O, one side must move down 7.5”, and the other side must move up 7.5”, for a total of 15”.

-Read the percentage of flow off the inclined scale.  If that percentage doesn’t fall within the range of about 55 to 85 percent, its probably best to resize the orifice.  For instance, if the reading is 50% or less you probably need a smaller orifice.  If the percent is 95% or more, you probably need a larger orifice.

-If you are trying to test over a range of valve positions like I did, you need to fiddle with the orifice size until you find a size that lets you stay on the graduated scale for the whole test.  I ended up using a 66.7 CFM orifice to allow me to remain within to 50 to 100% range of the scale.  Anything under 50% or over 100% becomes a guess because there are no fine graduations in those zones.

-Each time you take a reading you must readjust to your desired test pressure first, then take the reading.  For instance, if testing flow for increasing valve open positions (say from .100” to .400” in .050” increments) start at .100”.  Adjust the bleed valve/s to achieve test pressure as read on the u-tube (15” H2O worked good for me).  At steady test pressure, read the inclined manometer and record the reading.  Proceed to the next increment (.150”).  You will note that the test pressure drops off.  Readjust the bleeds to the desired test pressure before you take your reading for .150”.  Once test pressure is steady, read the inclined manometer and record the reading.  Continue in this manner, always reestablishing test pressure before you take the reading.

I also want to mention that while I was working on this project I stumbled across a new book by David Vizard.  I have several of his books and this latest one, “How to Port & Flow Test Cylinder Heads”, discusses the advantages of using a “Floating Pressure-Drop” method of testing.  This method essentially recognizes that a typical port/valve is subjected to high pressure differentials at low lift and progressively decreasing pressure differentials as the valve opens farther.  Hence, just sucking on it with a vacuum cleaner, letting the test pressure degrade, and not reestablishing test pressure before taking a reading, more closely replicates real world conditions.  I agree with that concept.  But in my opinion, having the ability to always test at the same pressure allows me to more closely monitor and evaluate my progress (or lack of progress).  It certainly is an interesting argument and I intend to explore it further.  

This is well worth the tech section.

Awesome!