Home Made Manometer

I'm still working my way through all the details of tuning my 1300. On
Saturday I finally got my home made manometer to start working. It's
not perfect but works well enough.



Next step will be to replace the vacuum gage with a more sensitive
unit. The mason jar with the custom lid worked fine at damping out the
pulses.

I was able to identify that the 1_2 carb was a bit behind the other
two, it had a slightly higher reading. I opened it a bit and all three
started reading the same.

KZCSI

The danger with using a single gauge set up is that the throttle butterflies affect each other on CV carbs and the slide actuators affect each other on mechanical slide carbs. When you loosen up one, the others may drop down... Also, when you sync four cylinder CV carbs, you do them as follows:

sync 1 & 2 to each other

sync 3 & 4 to each other

sync 1&2 to 3&4

That is why there are only three sync adjusters on a four cylinder. How many on a 6 cylinder? Are there five? If I had a six, I think I would just buy two manometers of the same type and use 1.5 of them. Hope t his works for you...

Hi George,
I guess I don't understand the problem. I've got a tube connected to each intake, the engine is warm and idling. I open one valve at a time and I can see the vacuum in that tract. I work my way across the engine. If there's any differences in the vacuum from cylinder to cylinder I see them. The value of using one gauge is that I'm able to connect the same gauge to each cylinder without doing anything more than opening and closing a tiny pair of valves.

KZCSI

one guage is not going to be the best way to set the carbs, you want to balance all of them at the same time, and I have seen it when you adj one carb it might affect the rest of them just a tad.
I built one out of 4 gauges years ago, it didnt work as well as the mercury stick

The problem is that you have to assume that all four channels are the same. That's a big assumption. With the four sticks, you can see all of them at the same time and that allows you to calibrate the gauge. There is no way to check all four of your channels at the same time in order to compare and calibrate your gauge.

If you've ever calibrated a gauge then you know how far off calibration they are when they come from the store. They have to be normalized so that equal vacuum pulses give equal readings. There is no way to do that in your single-gauge setup.

If the vacuum was a pure steady vacuum, then your rig would be fine. But vacuum in pulses is affected by the restrictions (and capacity of tubing) in the path.

Are your readings the same because you have equal engine vacuums? Or are they the same because the restrictions in your gauge paths are making them appear the same? You can't answer these questions on your single rig. But 4 gauges, simultaneously, will answer those questions (through the normalization process).

Hi Guys,
Thanks for your input and this thing is still a work in progress but:

The single gage has pluses and minuses. For one the single gage need not be calibrated, it only needs to read the same every time it's exposed to a vacuum of the same pressure. The four or six individual gages might well not agree with each other and thus might send the user hunting for a difference in pressure that doesn't exist. Another plus is that this setup works on my six. On the minus side I have to close a valve and open another to read the vacuum at a different cylinder so I can't look at more than one at a time.

At first I didn't have the mason jar at all and I had to depend on minute openings of the valves to damp the oscillations. Next I added the mason jar but it was just "Teed" into the system. Finally I realized that if I routed the vacuum into the mason jar and then read the vacuum off of it it would serve to damp out the oscillations, which it does just fine.

By the way the tubes are insignificant as once the air flow stabilizes the pressure becomes even throughout the system.

KZCSI

I'm going to play around with it this evening to see if I hook the gage up directly to the intake, with a metering valve, and see if the length of the tubing affects the reading.

Thanks

KZCSI

KZCSI wrote:

I'm still working my way through all the details of tuning my 1300. On
Saturday I finally got my home made manometer to start working. It's
not perfect but works well enough.

Next step will be to replace the vacuum gage with a more sensitive
unit. The mason jar with the custom lid worked fine at damping out the
pulses.

I was able to identify that the 1_2 carb was a bit behind the other
two, it had a slightly higher reading. I opened it a bit and all three
started reading the same.

KZCSI

Bill, thats a hell of a jelly maker you got there.:woohoo:

the more I look at I think hes got a still working there:woohoo:

I'm not saying the single gauge needs to be calibrated.

I'm saying the tubing, valves, resrtictors, and connectors need to be calibrated so they all produce the same reading, given the same vacuum. They are not all identical, so will not react the same to vacuum pulses. But, because you only have one gauge, you can't calibrate the tubing, valves, resrtictors, and connectors simultaneously, for all four channels.