su carbs

SU's are some of the best carbs in history. There are smaller jets avail...I've been out of the scene for a long time. I'm a Datsun 240Z freak and worked on a lot of SU's. If you get the perfect solution to tuning the SU's for HHO with smaller jets or whatever you do, please please please post.

sorry for typos. fingers an thumbs a little sore after not looking at the soldering iron when going to pick it up OUCH!!!!!!!!!!

been a long time since i played with SU's, but you could look for smaller ones, IE: twin SU setup off a mini 1100 or something. could be an easy fix.
other wise i think your looking at a re-jet.

on a slightly different note, using an old brittish engine is going to be key i think, they were so over engineered they should hold up to anything hho wants to throw at it.
I have a mini 995 in the shed for my hho only prototype.

the old british engines are solid. took 28psi of boost to deliberately kill my last one so they are well suited to the to the extreme rise in combustion pressure hho introduces. for this project i'm not aiming for lots of power (like usual) instead just extreme economy. i'm aiming for 2000k's to 70 litres of fuel and user friendly engine charecteristics. be interesting to see how much water it will take to do the 2000 k's of normal driving. i'll still be using some petrol with a bit of canola oil to stop the engines valves from drying out. i think its very achievable with a bit of work and some outside of the square thinking.

Jetting

You should not have to worry about the jetting that much. An EFI engine fights to defeat the gains by adding fuel as seen needed from the O2 reading. That being the added O2 in your system from your HHO booster. You will not have that problem. On a carb engine the extra O2 is a plus. You wont need to jet down as much as you think or not at all. The savings in fuel simply comes from the throttle blades not being cracked as much and the additional hydrogen from your HHO cell. You will be getting a ratio of about 66% hydrogen and 33% extra oxygen added to the mix. The hydrogen is adding the fuel and the oxygen is leaning out your A/F mixture at the same time. Hence your savings. Now, you did say Maximum fuel mileage! This may be one solution. For that, jetting down or simply adjusting your powervalve assemby in your carb by the spring rate to open later or high vacuum. Or a height adjustment by bending the mechanism if that is an option. I'm not sure what powervalve or enrichment valve type this carb you're using has. I prefer the spring rate myself, sometimes stretching it some is all it takes. (I'm taking it that the jets are not easily obtainable.) I have used this method for 20+ years to tune the famous Q-jet for max mileage. Best of all, all the fuel you need is still on demand when you get in the throttle a bit more. Given the size of engine you are dealing with, the HHO amount wont have to be over 2 L/M making easier tuning. One thing to watch for on these small engines is the way they backfire from being lean just coming off idle. You will complicate this as you take more main jet away. Just be sure to add some fuel with the accelerator pump and this would avoid the hydrogen in the intake at the time from being ignited. I have a friend with a 468 ci big block Chevy that is concerned with fuel mileage lately for some reason or another. We are going to place a system just like you have described and see what comes of it. His tuning is a lot simpler with the power valves and numerous jets in hand. My results have yet to be proven fully but the theory sounds as if will work. I will post as soon as real world testing is completed.

Missed something

Sorry. I missed the part about the air bypass, That was main reason I was stating the other facts of tuning. Could you use an EGR valve with a fabicated type of opening rate? I don't know if this engine had an EGR system on them. But the carb engine in my friends does and that will be the route we use to start with. There are many vacuum type EGR's that can be fabricated to flow air as needed based on engine vacuum. Wide open throttle would release vacuum and close the valve to prevent an overly lean burn, and at high vacuum cruising, start cycling the extra air into your intake. This would be a way to compensate. If it was all vacuum operated, then once you have the right amount of air going in, you would only have to check or adjust occasionally. I still don't think much air would be needed, but someone has to try it to find out. It sounds as if you have the ability to fab something like this up since you have dealt with turbos and I've never seen a "bolt on turbo kit".