Yes, I was thinking of experimenting with the 66 mustang/289. Carbs are easier to work with than fuel injection. I've been doing a lot of tests and experiments this week with vacuum. Mostly for best timing, but also for things like HHO and Water Injection.
Manifold pressure is definitely highest at idle. It doesn't ever really reach "0" at higher RPM's however. It would however not be enough vacuum for say water injection that requires enough vacuum to suck air through and create the air bubbles and the water mist. However, it looks like manifold vacuum would be OK for an HHO setup. The HHO setup doesn't use air to create the hydrogen. It is created with electrolosys. So, even with a low level of vacuum, it would be enough to pull the hydrogen into the intake.
Using timed/ported vacuum (Side of carb usually going to distributor) is a catch-22. It depends on the type of
distributor you are using and to what extent you use vacuum advance. There are basically 2 types of timing advance. (Doesn't matter if it's a traditional points
distributor or a newer HEI style). You can have a lot of mechanical/centrifugal advance in the weights of the distributor; e.g. 15L each which is 30 degrees of advance; plus your static/initial timing of say 6 degrees BTDC; giving you the 36 degrees total timing you want; in my case with my 289 engine. Then, you would probably use the manifold vacuum for that
distributor because at idle, the weights haven't kicked in yet, and as you excellerate, the vacuum assists advancing timing until high enough rpms where vacuum decreases and the weights in the mechanical/centrifugal take over. This would free up the timed/ported to be used for the HHO and everyone would be happy.
However, if you had a stock
distributor with vacuum advance, or a new HEI like I have, then you need to use the ported/timed vacuum. That's because the mechanical/centrifugal advance is only about 20 degrees. Plus the 6 degrees btdc for static/initial. Your vacuum advance is either a fixed amount of about 10 degrees, or if it's adjustable like mine, I adjust the vacuum advance for about 10-12 degrees. This way, as you accelerate, you get full vacuum, and your total advance goes to about 36-38 degrees which is what I want. As I drive, the ported/timed vacuum maintains vacuum and I maintain my timing advance for the car to run most efficiently.
If however I tap into this vacuum line, I would have to regulate the amount of vacuum that I would allow to be used by the HHO. It shouldn't be a problem, but definitely has to be factored in. For instance. My manifold produces a max vacuum of approximtely 17 hg. For my vacuum advance, set to 10-12 degrees to function properly, I need approximately 12-13 hg of vacuum minimum. So, that means I have about 4 hg of vacuum left. If that's enough for the HHO to be brought into the intake, (WHICH I THINK IT IS), then that's fine. But, you would have to regulate it with a small regulator like used in a fish tank to regulate the air circuilator. If you don't regulate it, then the vacuum with equalize pressure between the HHO Browns generator and the distributor's vacuum advance. The HHO generator would be fine, but I wouldn't have enough vacuum to advance my
distributor far enough, and would totally defeat the purpose of the HHO because I would be running the car to far retarded. Without regulating the vacuum to the HHO, the equalized balance would be about 8 hg to each of the HHO and the distributor. Experimenting showed that 8 hg of vacuum on my vacuum advance, even if adjusted to the most forgiving, would only provide about 3 degrees of advance.
Without regulating the vacuum, I would either have to change my
distributor weights and go with manifold vacuum and use the ported/timed for the HHO; or, I would have to change the weights in the
distributor and take in account of only about 3-4 degrees of vacuum advance. This would be counter productive. The whole purpose of vacuum advance is to produce more advance during acceleration, loads, hills, etc... and thus giving a much better fuel economy. Not too much of a problem if you live in Kansas or Nebraska living in the flat lands. But, a simple $2 adjustable air valve for a fish tank in line between the HHO output and the vacuum line is simple to do. All you have to do is to get a vacuum gauge, open the
distributor cap, manually pull vacuum on the vacuum advance and measure how much vacuum is required to make the vacuum advance open 100% of whatever it's set at. (It will stop moving). Then read the amount. Then, take the vacuum line that normally goes to the vacuum assist and with the
engine running, measure the max amount of vacuum at high rpm. If it's considerable MORE than what was required to activate the vacuum advance; the us a adjustable valve on the HHO side to allow more than enough to the
distributor and the remainder to the HHO generator. Good luck.... Mike.....
