SuzukiSavage.com - Print Page

SuzukiSavage.com
/cgi-bin/YaBB.pl
General Category >> Technical Documents/Reference >> Valve & Guide Test - Budget Flow Bench
/cgi-bin/YaBB.pl?num=1538442855

Message started by DragBikeMike on 10/01/18 at 18:14:15

Title: Valve & Guide Test - Budget Flow Bench
Post by DragBikeMike on 10/01/18 at 18:14:15

This is a very long post with lots of pictures. Please hold your comments and questions until I have made the final entry, which will be obvious.

In preparation for future performance upgrades, I decided that I was going to need a better tool to measure improvements in air flow. I want to improve the cylinder head flow. I could always just hack away at the ports, valves & guides, but it seems more prudent to try and see if I can monitor the changes to verify that they are in-fact improving flow. It’s very hard to put the material back on once you grind it off.

Armen was gracious enough to send me a sectioned LS650 cylinder head to play around with. It had been subjected to one of those disconnected cam chains that we keep reading about on the forum. As such, it was toast, so Armen seized the opportunity and cut the thing in half, right smack down the center of the ports. It’s a thing of beauty. You can now really get your eyeballs around the problem areas.

Fast 650 held my hand through the basics of port flow and served as a mentor. He is a fabulous resource and provided a wealth of hard-earned knowledge on the ins & outs of cylinder head mods. He fixed me up with a great article from an outfit named “DTec” that provides all the details for fabrication of an inexpensive flow bench.

Up to this point, I was trying to measure my flow improvements by simply attaching a vacuum cleaner with a u-tube water manometer in-line. It worked OK and I could pretty much see big changes in pressure which indicate a change in flow, but I had no way to keep the test pressure constant, and the resolution on the manometer was poor. Also, changes in atmospheric conditions and variations in line voltage and frequency seemed to make repeatability difficult.

After reading the DTec article on the DIY flow bench three or four times, I felt that I could fabricate a very simple tool that would allow measurement of flow with good resolution so that very small changes (good or bad) would be easy to detect. The tool would also allow me to test each change at exactly the same pressure, so there would be no doubt about other things affecting the results (things like atmospheric pressure, humidity, temperature, electrical voltage & frequency, vacuum cleaner performance, etc.). If you always adjust to the same test pressure, the playing field will be level, and the results should be consistent and accurate.

I used the info in the DTec article to fabricate a smaller and cheaper version of their flow bench. I wanted something that would be very simple, compact for easy storage, provide good resolution to make interpretation fool proof, cheap (of course), and not necessarily accurate. I’m not worried about accuracy in terms of cubic feet per minute (CFM). All I want is a tool that shows me if I made the flow better, or if I made the flow worse. I want the tool to give consistent, repeatable results. The budget flow bench meets those requirements.

Title: Re: Valve & Guide Test - Budget Flow Bench
Post by DragBikeMike on 10/01/18 at 18:15:53

Here is a sketch of the budget flow bench.

Title: Re: Valve & Guide Test - Budget Flow Bench
Post by DragBikeMike on 10/01/18 at 18:17:30

The sketch is pretty crude but I think it will do. The heart of this system is the orifice with an inclined manometer that measure the difference in pressure across the upstream and downstream sides of the orifice. I used the DTec article to provide the various sizes for the orifice and also the details for the scale on the inclined manometer (very important, won’t work without the scale).

The orifice and inclined manometer are a team, and they really don’t care what the test pressure is. They only sense flow. The inclined manometer scale is graduated in a manner that provides an accurate reading of the percentage of flow associated with a given differential. This relationship between percentage of flow and differential pressure remains the same, regardless of orifice size or test pressure.

Title: Re: Valve & Guide Test - Budget Flow Bench
Post by DragBikeMike on 10/01/18 at 18:18:26

Here is a picture of the completed rig.

Title: Re: Valve & Guide Test - Budget Flow Bench
Post by DragBikeMike on 10/01/18 at 18:20:46

I will provide the details about the rig and its construction later in this post. For now, let’s get to the meat of the tests.

I wanted to test valves and guides to see what low hanging fruit might be available. These parts are easily removed and easily replaced. If I perform a mod on a valve or a guide, and I don’t like the results, I can simply throw the part away and install a new one. If I grind on the head and I don’t like the results, it gets expensive real fast. The guides and valves provided good test specimens to play with. They also allowed me to practice and learn more about how to set-up and operate the rig.

The stock exhaust valves are typical. They are 1.1” diameter and have 7mm stems. I had two old junk Honda valves laying around and they just happened to fit Armen’s head. So, I left one valve with stock geometry and I did a 30 degree back-cut on the other.

Here is a picture of the valves.

Title: Re: Valve & Guide Test - Budget Flow Bench
Post by DragBikeMike on 10/01/18 at 18:22:07

The stock valve guides are crude at best. They are blunt with no attempt made to streamline their profile. Who knows, maybe the stock guides will work the best. Here is a shot of what I refer to as “Blunt Force Trauma”. That gash in the head is definitely blunt force trauma but I’m actually referring to the hot gasses blasting straight into the blunt face of the guide.

Title: Re: Valve & Guide Test - Budget Flow Bench
Post by DragBikeMike on 10/01/18 at 18:24:22

The exhaust gas flows directly at that guide. We might be able to improve things by simply tapering or rounding the guide.

Her is another view looking through the port outlet. See that nasty blunt guide sticking out of the guide boss? We should be able to improve that.

Title: Re: Valve & Guide Test - Budget Flow Bench
Post by DragBikeMike on 10/01/18 at 18:25:29

I removed the stock guide from the head and then I made four dummy guides with various geometries. One was blunt to replicate the stock guide, one was tapered, one was radiused, and one had a half-taper (to simulate leaving the guide in place and simply grinding it a bit to blend into the boss). I intended to use the blunt guide not only to replicate stock conditions, but also to simulate how things would flow if the stock guide were ground flush with the boss. To achieve the flush condition, I simply installed a nylon washer under the spring seat. I personally expected the tapered guide to flow the best. All the test guides had their OD skimmed so they could be easily removed and replaced (no press fit).

Title: Re: Valve & Guide Test - Budget Flow Bench
Post by DragBikeMike on 10/01/18 at 18:27:29

I tested ten combinations, five with the stock valve, and five with the back-cut valve. The inclined manometer reads out in percent. So, if you are using a 100 CFM orifice, and the manometer reads 81, then the flow across the orifice is 81 CFM (.81 x 100 = 81). Keep in mind that the CFM numbers are not accurate. This contraption is not calibrated. However, I believe that the change in CFM from one combination to the next is pretty accurate. Anyway you look at it, the contraption certainly shows that improvements are lurking in the guides and valves.

Here are the results of the first five tests using a valve with stock geometry.

Title: Re: Valve & Guide Test - Budget Flow Bench
Post by DragBikeMike on 10/01/18 at 18:28:49

As you can see, the flush guide performed best with the tapered running second. The half-taper performed worse than the stock guide. Don’t ignore those low lift numbers. They are important to overall performance.

Here are the results of the next five tests using a valve with a 30 degree back-cut.

Title: Re: Valve & Guide Test - Budget Flow Bench
Post by DragBikeMike on 10/01/18 at 18:31:01

Once again, the flush guide performed best. If you calculate the percent of flow to actual CFM, you find that the flush guide with back-cut valve flows about 2 CFM better than stock at low lift and about 1.3 CFM better at max lift. I’m only testing one exhaust valve so if both valves are considered the improvement works out to about 3 to 4 CFM. Not earth shattering but it’s a cumulative process. The final package is the result of many small improvements. As they say, every little bit counts.

I ran some special tests just to fool around. I initially borrowed Armen’s head to see if I could fabricate a removable insert to bridge the gap between the 1.3” opening in the exhaust port and the 1.27” inner pipe in the exhaust header. The intent was to eliminate the immediate & drastic increase/decrease in the cross section between the port and inner header pipe. So, I did one test with a plastic insert that tried to simulate the insert I had in mind. It didn’t work too good but it’s hard to do a proper test with only half-a-port. I also did a test on the half-tapered guide where I reversed its position 180 degrees. That flowed better than when it was installed as intended. Finally, I filled in the threaded hole for the head stud. I used modeling clay to fill the hole and smoothed it flush with the surrounding port material. That flowed the best at high lift.

Here are the results of the special tests.

Title: Re: Valve & Guide Test - Budget Flow Bench
Post by DragBikeMike on 10/01/18 at 18:31:57

Here is a graphical representation of the stock guide & valve vs the two best flowing combinations.

Title: Re: Valve & Guide Test - Budget Flow Bench
Post by DragBikeMike on 10/01/18 at 18:33:36

The Budget Flow Bench is intended to be set up with the cylinder head resting on top. Then you suck through the head to test the intake ports, and you reverse the flow and blow through for the exhaust ports. For the tests I did, I had to suck through the exhaust port (in the normal direction of flow) because I only had half-a-head. I’m pretty sure the results may be a bit different once I test a complete head as intended.

To be able to test in both directions, I will have to add a bleed valve chamber so that when blowing through a test specimen the bleed valves will be located on the vacuum cleaner exhaust rather than the cannister (which is on the suction side of the impeller). The manometer lines will also have to be reversed.

This sketch shows it configured for blow-thru.

On 1/15/19 I changed the sketch. I had the u-tube hooked up to the wrong side of the orifice. It should be connected between the test specimen and the orifice because the u-tube is supposed to measure the differential across the test specimen.

Title: Re: Valve & Guide Test - Budget Flow Bench
Post by DragBikeMike on 10/01/18 at 18:36:12

If you want to make one of these rigs, I suggest you get on the web and look up www.dtec.net.au. Then go to “technical articles include” and “follow this link to review these articles” and select “Airflow Bench Design – DIY”. The article includes a nice Excel spreadsheet that will calculate the exact measurements for your inclined manometer, conversion charts for various test pressures, and of course the nitty gritty on exactly how their flow bench works, how to use it, construction details, etc. Theirs is a really nice, professional unit.

If you just want a simple and cheap tool to get started, the rig outlined below fits the bill. I would read the DTec article first (several times) to get a good understanding of the operating principles.

The rig is fabricated from 4” ABS pipe. You will need a twelve inch section of pipe (cut it in half so you end up with two six-inch sections), a 4” cap, a 4” coupling, four 3/16” vacuum tees, a 4” closet flange, five or six 4” test plugs, about 15 feet of 3/16” nylon tubing, and a 2” x 1-1/4” PVC bushing (the bushing ID should be enlarged to about 2” and any sharp edges on the ID blended to provide smooth flow).

Here is a picture of the finished PVC bushing.

Title: Re: Valve & Guide Test - Budget Flow Bench
Post by DragBikeMike on 10/01/18 at 18:37:09

Use a hole saw to cut a 2-3/8” hole in a section of the 4” pipe to accept the PVC bushing. Cut the hole with the end cap in place to make sure that the edge of the end cap doesn’t overlap the hole for the bushing. The vacuum cleaner hose will be attached to the bushing.

Title: Re: Valve & Guide Test - Budget Flow Bench
Post by DragBikeMike on 10/01/18 at 18:38:16

The bushing gets inserted from inside the 4” pipe.

Title: Re: Valve & Guide Test - Budget Flow Bench
Post by DragBikeMike on 10/01/18 at 18:39:18

Then a piece of rubber hose is pushed over the bushing. The hose holds the bushing in place and serves as a flexible connector for the vacuum cleaner hose.

Title: Re: Valve & Guide Test - Budget Flow Bench
Post by DragBikeMike on 10/01/18 at 18:40:16

Drill two 5/16” holes in each section of 4” pipe. These holes will be used for installation of the vacuum tees. The holes are located about 2” from the edge of the pipe section. Make sure the edge of the coupling does not overlap the holes when the coupling is fully seated.

Title: Re: Valve & Guide Test - Budget Flow Bench
Post by DragBikeMike on 10/01/18 at 18:41:14

Modify the 3/16” vacuum tees by plugging two of the three holes in each tee with small screws. Then drill four .040” holes (#60 drill bit) in each Tee as shown. Epoxy the vacuum tees into the holes. Be careful not to plug the small .040” holes with epoxy.

Title: Re: Valve & Guide Test - Budget Flow Bench
Post by DragBikeMike on 10/01/18 at 18:42:12

Here’s what the tees look like once epoxied into the pipe. Note the small .040” holes.

Title: Re: Valve & Guide Test - Budget Flow Bench
Post by DragBikeMike on 10/01/18 at 18:43:21

The 4” test plugs will be used to make orifice plates of various sizes to suit the flow requirements of whatever you wish to test. You will select an orifice that can provide a flow that will result in a reading on the inclined manometer that falls somewhere within about 55 – 85 % at the desired test pressure (ideally 15” H2O) read on the u-tube manometer.

Here's a picture of a blank test plug.

Title: Re: Valve & Guide Test - Budget Flow Bench
Post by DragBikeMike on 10/01/18 at 18:44:17

Here is a picture of several orifices made from test plugs.

Title: Re: Valve & Guide Test - Budget Flow Bench
Post by DragBikeMike on 10/01/18 at 18:46:12

Orifice sizes and their associated flow are as follows:

51.85 mm = 209.5 CFM
42.38 mm = 139.5 CFM
29.98 mm = 70.4 CFM
21.16 mm = 35.5 CFM
9.92 mm = 7.8 CFM

You can make orifice plates with several sizes of holes and combine the flows to get a desired total flow. For instance, if you use a plate with one 21.16 mm hole and one 9.92 mm hole, the orifice plate flow rating will be 43.3 CFM (21.16 + 7.8 = 43.3). When you do a test, if you want to get a feel for how much air you are moving simply read the percentage indicated on your inclined manometer and multiply the orifice flow rating by the percentage. Keep in mind that the contraption isn’t calibrated. I also did not follow all the specifics outlined in the DTec article. It’s intended primarily to show whether mods result in improved flow, and to be able to do meaningful comparisons. If you are looking to capture precise flow numbers, this ain’t the tool for you.

The orifice plate gets installed next. The size will depend on what you are testing. More on that later.

Title: Re: Valve & Guide Test - Budget Flow Bench
Post by DragBikeMike on 10/01/18 at 18:47:10

Then install the 4” coupling.

Title: Re: Valve & Guide Test - Budget Flow Bench
Post by DragBikeMike on 10/01/18 at 18:48:15

Next install the upper section of 4” ABS pipe.

Title: Re: Valve & Guide Test - Budget Flow Bench
Post by DragBikeMike on 10/01/18 at 18:49:09

And then either the closet flange,

Title: Re: Valve & Guide Test - Budget Flow Bench
Post by DragBikeMike on 10/01/18 at 18:50:00

or adapters to suit whatever you are testing.

Title: Re: Valve & Guide Test - Budget Flow Bench
Post by DragBikeMike on 10/01/18 at 18:51:05

The flow source for the rig is a ShopVac. Most of us have one of these. To have fine control over the test pressure you will have to drill a few holes in the vacuum and install bleed valves.

Title: Re: Valve & Guide Test - Budget Flow Bench
Post by DragBikeMike on 10/01/18 at 18:52:03

Don’t worry, the holes are easy to plug. If you don’t want to spring the big bucks for the valves, you can make inexpensive bleed valves from PVC pipe and fittings.

Title: Re: Valve & Guide Test - Budget Flow Bench
Post by DragBikeMike on 10/01/18 at 18:52:58

Use a short section of pipe with a coupling slipped over. Sand out the bore in the coupling until it slips easily over the pipe. It needs to rotate freely. Then drill big holes through the pipe and coupling. When you rotate the coupling, you close off the hole.

Title: Re: Valve & Guide Test - Budget Flow Bench
Post by DragBikeMike on 10/01/18 at 18:56:10

For the budget bleed valves, use appropriate PVC adapters and caps to suite your application. Lubricate the rotating coupling with silicone grease to make it smooth and easy to turn. The hose clamp is used as a lever or handle to grab when you want to open or close the hole.

Use the DTec article and the Excel spread sheet to fabricate your inclined manometer. Its simply a slab of plywood, some 3/16” nylon hose, a free syringe body from the drugstore, and a 14” strip of aluminum angle.

Title: Re: Valve & Guide Test - Budget Flow Bench
Post by DragBikeMike on 10/01/18 at 18:58:31

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.

Title: Re: Valve & Guide Test - Budget Flow Bench
Post by DragBikeMike on 10/01/18 at 19:01:03

Same problem. It auto rotates. Just turn it 90 degrees CCW in your head. I'm sure you'll get the idea.

Here's a shot of the reservoir (syringe). Hope it doesn't turn.

Title: Re: Valve & Guide Test - Budget Flow Bench
Post by DragBikeMike on 10/01/18 at 19:02:44

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.

Title: Re: Valve & Guide Test - Budget Flow Bench
Post by DragBikeMike on 10/01/18 at 19:03:43

When everything is set up it looks crazy, but it works pretty good.

Title: Re: Valve & Guide Test - Budget Flow Bench
Post by DragBikeMike on 10/01/18 at 19:06:14

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.

Title: Re: Valve & Guide Test - Budget Flow Bench
Post by DragBikeMike on 10/01/18 at 19:07:11

For testing with the valve open at different increments, a soft checking spring needs to be installed along with a simple jack tool. I used it with a dial indicator to position the valve exactly. It uses a ¼”-20 UNC screw. If you don’t have a dial indicator you can count turns. Every turn equals .050”.

Title: Re: Valve & Guide Test - Budget Flow Bench
Post by DragBikeMike on 10/01/18 at 19:12:48

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.

Title: Re: Valve & Guide Test - Budget Flow Bench
Post by DragBikeMike on 10/01/18 at 19:15:59

Like most things done on a budget, this thing has limitations.

As I’ve already mentioned, it’s not going to provide accurate flow data in CFM. It will provide conclusive performance info related to changes you make, and that information will allow you to consistently see how your changes perform (better, worse, no change, etc.). It will allow you to collect numerical data that can be compared from one test to the other. It will allow you to display your data graphically to permit better interpretation. It will allow you to take measurements under identical conditions which ensures repeatable results. If you have a yearning for accurate data, you can take your orifice plates to an establishment that has a known accurate flow bench and have them test your orifice plates. The DTec article has additional info regarding orifice calibration.

The vacuum cleaner limits flow capacity. Best as I can figure, its only going to pull around 100 CFM and that’s with only 0.75” H2O test pressure. With the test rig open ended (4” to 2” reducer installed with no test specimen, end of reducer fully open), an orifice rated at 139.5 CFM, test pressure on the u-tube at only 0.75”, and all bleed valves closed (i.e that’s all she’s got), the inclined manometer read 71%. That works out to around 99 CFM. Testing at only ¾” H2O would result in velocities that are way too low to replicate real world conditions. So, I’m thinking that testing at valve lifts of more than .150” will have to be done on a single valve rather than both at the same time. That method will not test the flow characteristics when the two flows converge. I will cross that bridge when I come to it.

Title: Re: Valve & Guide Test - Budget Flow Bench
Post by DragBikeMike on 10/01/18 at 19:17:48

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.

Title: Re: Valve & Guide Test - Budget Flow Bench
Post by DragBikeMike on 10/01/18 at 19:18:39

I want to thank Armen and Fast 650 for all their help. Without their assistance I could never have come up with my contraption. It’s been a great learning experience and now I have a cool tool to help me better understand what’s going on in my engine. This thing has the potential to test all sorts of components.

I hope you find this report beneficial.

Title: Re: Valve & Guide Test - Budget Flow Bench
Post by verslagen1 on 10/01/18 at 21:24:42

This is well worth the tech section.

Title: Re: Valve & Guide Test - Budget Flow Bench
Post by Dave on 10/02/18 at 04:24:38

As usual......great research and analysis.

Early engines had blunt valve guides, at some point Suzuki changed that and the guides got a taper on later models.

The valves heads are very thin at the outer edges and have a hardened surface - and the valve wearing surfaces cannot be refreshed by grinding. I wonder if the back cut for improved flow is permissible - will the exhaust valve still be reliable? (The failures I have seen on the Savage are from the head coming off the stem.....not from any burning of the valve edges).

Title: Re: Valve & Guide Test - Budget Flow Bench
Post by Armen on 10/02/18 at 17:51:07

Awesome!

Title: Re: Valve & Guide Test - Budget Flow Bench
Post by sparktfxr on 10/09/18 at 03:11:53

Fantastic effort!...well done

Title: Re: Valve & Guide Test - Budget Flow Bench
Post by DragBikeMike on 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.

Title: Re: Valve & Guide Test - Budget Flow Bench
Post by DragBikeMike on 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.

Title: Re: Valve & Guide Test - Budget Flow Bench
Post by DragBikeMike on 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.

Title: Re: Valve & Guide Test - Budget Flow Bench
Post by DragBikeMike on 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.

Title: Re: Valve & Guide Test - Budget Flow Bench
Post by DragBikeMike on 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.

Title: Re: Valve & Guide Test - Budget Flow Bench
Post by DragBikeMike on 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.

Title: Re: Valve & Guide Test - Budget Flow Bench
Post by DragBikeMike on 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.

Title: Re: Valve & Guide Test - Budget Flow Bench
Post by DragBikeMike on 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.

Title: Re: Valve & Guide Test - Budget Flow Bench
Post by DragBikeMike on 01/26/19 at 19:45:47

Here's the intake data on the good head. Pretty close.

Title: Re: Valve & Guide Test - Budget Flow Bench
Post by DragBikeMike on 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.

Title: Re: Valve & Guide Test - Budget Flow Bench
Post by DragBikeMike on 01/26/19 at 19:49:52

Here is an illustration of how the suck through setup is configured.

Title: Re: Valve & Guide Test - Budget Flow Bench
Post by DragBikeMike on 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.

Title: Re: Valve & Guide Test - Budget Flow Bench
Post by DragBikeMike on 01/26/19 at 19:53:50

Here's the graph on the good head. Pretty close again.

Title: Re: Valve & Guide Test - Budget Flow Bench
Post by DragBikeMike on 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