After looking online for a new 6 gang manometer and having no luck finding one. And after looking online at some examples of home made manometers, I decided to build my own. Being the old scavenger and hoarder that I am, there were a few things just laying around here that I could use and that helped to keep the cost down.
Here is my Manometer:
It seemed that every article I read about home made manometers was using some restriction in the vacuum lines to minimize the fluctuation of the fluid. Also, most of the articles had given some thought to the possibility of sucking some of the manometer fluid into the engine. Yikes! That is not a happy thought.
So I began to think of ways to contain the fluid so it would not be possible for it to get into the engine. In the process, I realized a larger volume of air in the line between the intake and the manometer itself would act as a damper to the engine vacuum pulses thereby eliminating the need for restriction in the line. Both problems are solved by the simple addition of a catch chamber in each vacuum line heading to the intakes.
Supplies I used:
# One 2x6x36 - I would not make this any shorter. It was laying here so I used it but 42 long would be better I think.
# ¾ inch PVC about 199 inches of this. Figure 2 joints if you’re buying new
# ¾ inch PVC caps. 13 of these
# ¾ inch PVC elbow just one.
# ¾ inch PVC glue to thread end and PVC threaded plug. One each
# One tubing clamp for PVC
# Some old fishing line too stiff to cast with anymore but still good for tying things
# 5/16 OD x 3/16 ID vinyl tubing 18 ft long. Times 6 so I can leave the manometer on the wall and still hook the tubes to the bike.
# One automotive vacuum gage
# A couple of feet of ¼ by 1 and ½ plastic lath.
The rest of the stuff I used, I would do differently if I was gonna build another one. I am going to list these things here but will make a different suggestion later in this write-up.
# Six rigid acrylic tubes 3/8 OD x 36 long
# Six slip connectors for tubing (threaded on one end)
# About 6 feet of 3/8 OD x ¼ ID vinyl tubing
The work begins:
The board;
I cut 6 notches lengthwise in one side of the 2x6. I cut these 3/16 deep by 3/8 wide so that my vertical tubes would set about half way down in the board and the sides of the tubes would just touch the sides of these notches. I also cut a notch across the end of the 2x6 so that part of the manifold pipe would lay in it and could be secured there. This notch should be half the diameter of the ¾ PVC. I used ¾ PVC for pressure applications and that is a different diameter than PVC for drain applications.
I drilled 3/16 holes between each of the lengthwise notches and on the outside edge of each outside notch. These holes were drilled in three lines. One an inch up from the bottom, one an inch down from the top and one in the middle. The fishing line will go thru these to secure the tubes to the gage board.
With that done, I put a couple of coats of white paint on the board to contrast with the manometer fluid and make it show up well. After the paint dried, I used a square and marked out lines on the board at 1 inch intervals. Most of the lines are just ink pen but every 5th line is magic marker. The lines don’t really mean much but they do help to give reference.
The manifold;
Cut a piece of PVC to lay across the 2x6 with a cap on one side of the board and an elbow on the other side and cut another piece about 11 inches long to go up beside the board. Do not glue this together yet. You will want to drill 6 holes in the short piece to attach the vertical sight tubes.
Here is where I suggest you do different than I did. I used plastic fittings threaded on one end and the other end designed to be pushed onto tubing of almost any sort. They are not PVC so could not be glued to manifold pipe. I drilled and tapped the pipe on my manometer but these fittings just did not want to seal. Big PITA! Also, the rigid acrylic tubes are nice and clear but somewhat pricey.
If I was to do this again, I would just use The 3/8 OD vinyl tubing for the run from the manifold to the accumulators.
I found that drilling an 11/32 hole in the PVC and then forcing the 3/8 OD tubing into it creates a very good seal. No fittings and no extra cost. That is what I would do here on the manifold. Of course that means you will be using 18 feet more of the 3/8 OD vinyl than I did. But you will not be using the rigid acrylic nor the push fittings.
I like the ¼ ID for the vertical sight tubes of the manometer because the larger tubes are easier to see and because the volume of the ¼ ID tube makes a slower response than a smaller ID tube.
Be sure to get all 6 holes lined up straight in this pipe so it will fit to the board right. If you lay it on the bench and put one side up against a box or some other stop to hold it steady and then just lay a pencil on the bench and draw it along the pipe, you will have a straight line for the holes and will only have to measure lengthwise to space the holes to line up with the notches in the board. Do not forget to allow enough room for the cap on one end and the elbow on the other. Dry fit the PVC pieces to the board and when you have it lined up, put a mark on the elbow and the manifold tube to line up when you glue the pieces together. The 11 inch piece of ¾ PVC goes in the other end of the elbow and will stand along the edge of the 2x6 and be clamped at the upper end to the 2x6. The glue on threaded fitting goes on the top of that tube to be used as a fill point for the system. I drilled a 9/32 hole thru the plug that threads into the top of that fitting and forced a short piece of 5/16 OD by 3/16 ID vinyl tubing into it. The other end of this piece of tubing is connected to my old vacuum gage which had been laying around in my toolbox since sometime in the sixties. If your fittings and drilled holes all line up with the board right then go ahead and glue that and put it aside.
The accumulators:
Pretty simple here. Just cut 6 pieces of the ¾ PVC 30 inches long and glue a cap on one end. Drill a 9/32 hole about an inch in from the other end (just far enough in that it will not be covered at all be the cap to be glued on this end). Drill an 11/32hole in the 6 remaining ¾ PVC caps. Glue them on the pipes.
Miscellaneous brackets:
I used some plastic lath ¼ thick by 1 and ½ wide to make a hanger for the top of the manometer. Just drill a nice sized hole in one end to hook it on a nail or something and then 2 small holes for screws to screw it to the 2x6.
I cut 4 pieces 9 and 1/2 inch long to screw to the back of the 2x6 and hold/contain the accumulator tubes. 2 of these pieces go against the board and the other 2 work as clamp bars to sandwich the accumulators between. I drilled holes for 2 screws in the middle of these pieces and one hole in each end that I put wire ties thru to clamp the accumulators in.
I put a piece of the plastic in the vise and used a propane torch (very carefully so as not to burn) to heat it along a line and bend it 90 degrees. I drilled a couple of holes to attach one side to the 2x6 and I drilled one hole in the other side of this plastic bracket to stick the end of my vacuum gage thru. It makes a nice holder for this gage.
Assembling it all:
Lay out the position for the screw holes in the back of the 2x6 for attaching the plastic hanger hook you made and for the plastic pieces that will hold the accumulators. Be careful that none of the screws end up running into the vinyl tubing on the front of the board.
Cut 6 pieces of 3/8 OD vinyl tubing 4 feet 4 inches long. Put a mark on the vinyl tubing about 4 inches back from one end. Then push that end into the drilled end cap of one of the accumulators (30 inch pipes with caps) push it in to the mark. If any fluid gets sucked into this pipe, it will exit the vinyl tubing a few inches below the vacuum line going to the intakes. That should keep any accidental splash from entering the line to the intakes.
Note: if these drilled holes are cleaned up with a good deburr tool, the top of the holes should be rounded a little and this will help a lot when pushing the tubing in.
Push the other end of these vinyl tubes into the manifold pipe. Place the manifold pipe on the 2x6 and line up the vinyl tubing. Put the clamp on the upright part of the manifold assembly and screw it to the 2x6 and tie the vinyl tubing into their respective slots. Hang the accumulator pipes on the back of the 2x6. You may prefer to push the long 5/16 OD vinyl tubing pieces into the holes on the side of these accumulator pipes before putting the pipes in place and clamping them down. I found it easier to deal with one pipe at a time while pushing these tubes in. This 5/16 tubing just needs to go far enough into the pipe that it will seal and not be prone to back out.
When you have it all together, pour the fluid of your choice into the system thru the threaded plug. Lean the system a little to the side so you will get all the air out of the bottom of the manifold. Fill it to the top of this pipe and then install the plug. I put the hole here and ran a tube to my vacuum gage so I could get an overall vacuum reading on my engine and that just lets me keep some idea of engine wear over the years or maybe point out major problems in the works. I used ethylene glycol simply because it is the highest specific gravity of liquid after mercury and I had several gallons on hand. It has worked well for me but I would probably be just as happy with trans fluid.
This system is very touchy. Adjust carbs slowly and cautiously. A big turn on one screw can send fluid into an accumulator. If you do that often, you are going to want to put drain fittings in the bottom of the accumulator pipes.
Well that is about all I can think of. You have seen the pics of mine. You have heard my suggestions for a cheaper version that will also be much easier to build.
There are probably hundreds of ways to make one of these. Use your imagination and whatever you have on hand. Or not. If you have gotten any ideas from what I have done then that is why I took the time to write this up. Well, some people did ask.
If I did not explain something clearly enough, just ask or send me a PM. You folks have helped me a lot and I am happy to return the favor.
Wolf
