Anybody here think about this and try anything to improve atomization , especially in secondary side. I have drilled the pickup tubes like some of the Rochester books recommend. Funny thing I found another book that says don't do this. I have done it many times and never noticed much difference either way. I was thinking maby a screen in the discharge tubes, they seem rather crude. There is no booster in the secondary side, so it seems like a big fuel dump to me. It might be interesting to try to fit some sort of booster to the metal divider just under the notches for the discharge tubes. On the primary side the double booster is probably good enough, grinding a small step in the top of the booster should make an improvement.
Personally, I think those Rochester Quad guys were way smarter than me on about anything related to fuel and I try to not mess with it too much. There are plenty of horror stories of making a car slow down by "fixing" perceived deficiencies of the Qjet. I generally stick to changing jets, rods, hangers or float levels, fixing what's broken and leaving the rest alone. Your mileage may vary, literally.
the smaller emulsion tubes restriction can be opened up a bit to aid in aeration. if theyre originally about .025" open them to .028" or .035". some early secondary plenum divider plates had little boxes spotwelded onto them below the 2nd nozzles, maybe something could be added there? Edelbrock cut tabs onto the 2nd air flaps to help at WOT. check out a 1910 Qjet, it has little tabe bent on the back of the air flaps. just a few ideas.
I have seen the holes you are referring to in some I have pulled apart. I don't do this modification based on my understanding of the purpose of that fuel shot and with the holes, your sucking air, not fuel. It is basically a pump shot of fuel when secondaries open, and the wells will have only a small amount of fuel in them. I have also seen some modifications to the divider plates, but I have not heard of any testing to verify change.
When viewed from the side/cutaway, the air valve (flapper) creates it's own semi venture (booster) due to the shape. This mimics a cutaway of an airplane wing. The low pressure area created by accelerating the air causes fuel to flow from the discharge nozzle. Your ideas may work, but require expensive dyno testing or a/f meter. You can view the qjet design on the attached link, which is quite technical, but to download it costs $25. Good luck. http://papers.sae.org/660127/
I have taken apart a few turbo 4 barrel carbs, the sec discharge nozzles have a hole in about the middle , this would be before the divider, I m thinkin the purpose was for eariler delivery.
Add heavy x marks on the back of the air flap with the corner of a file. The fuel from the nozzles, blasts against the cross hatch scratches and helps fuel atomize. There will not be wet fuel just sliding off that flap! Figure at least 2 minutes labor time
Well, just scratch up it's bottom side where the pee hits it and nobody will see it. Keep the shiny side up, er up side shiny. LOL
I'm surprised some enterprising soul hasn't tried to market an atomizer nozzle to replace/afix to the thing. Personally, I've always been of the opinion that when feeding a liquid diet to a big beast, best to use a fire hose instead of a squirt gun. Hmm, I have a 7mm inspection camera. Perhaps I should record a full throttle blast with it pointing down the back barrels and again poked up into the intake from one of the vacuum taps on the back. Could be interesting information.
Brake specific fuel consumption: fuel volume required per horsepower produced. Maybe some dyno guys could tell about the fuel efficiency of a Qjet compared to the other carbs. I'm curious now I thought about it.
Adding holes to the emulsion tubes in no way cuts the sifon of fuel, The draw placed on it from a Buick 455 will overcome the four holes that some carb books describe. In fact they get sucked dry rather instantly either way, its your secondary accelerator pump. After thinking and reading all the good input from everyone here , the placement of the secondary discharge tube , the length that it sits past the divider, is important. When you drive them in , you can go all the way to the tube hanging in the middle, that would be max. Or the other way.. ... Its hard to say what depth give the most draw, I figure find this out , then just cut the other end just past the divider. I think the suction is sucking so hard that it barley even hits the butterfly. If your brave enough to stick your face over your carb and open her up, i think you can see it. I use the off to the side approach though.:idea2:
Something like an airaiter on your kitchen faucet. Just dont create restriction or less volume. If thats possible
I have one of these inspection cameras with a 45 mirror attachment that would be easy to snake into the breather and watch what happens when the quad opens up. I've used it down a push rod hole to make sure the lifters were oiling and down a spark plug hole to see if a motor had large or small valve heads. It is long enough to look at a whole host of things. For $26, you can perform your experiment with the laptop or android phone in the passenger's seat recording the run. http://www.amazon.com/gp/product/B0...camera 720P&qid=1447207655&ref_=sr_1_9&sr=8-9
that would be great but im still in the collecting parts stage of build, thats why i have the time to go through and maximise every part of the motor. I have run this carb with most of the mods done and it works kick ass. I have since opened it up a little more, made bigger primary blades , now im noticing some things not considered before . Like the placemint of the secondary discharge tubes, this looks like something that can really make gains if fully understood and placed in the best position. I m working on pics . but most should be able to know what im talking about.
Any body ever notice that the sec discharge nozzles end up rite under neath the sec butterfly shaft ? We'll they do . Has any one cut them to end up inmiddle of the space between the divider and the shaft . It would seem to be a better place. My car is not running Or I would have done this. I do not subscribe to the idea that GM did everything optimal to this carburetor.
It wouldn't actually take a running engine to produce the necessary data. Just a flow bench (or a shop dust collector) mated to the plate the quad mounts to then turn up the flow through the open rear barrels.
Allrighty then.. So what im going to do is use a shop vac , bolt the carb on a b4b , tape off all but one manifold port, fill the carb with gas. put the shnozzle to the untaped port and see how it looks going down the carb. On the carb i grinded away the sec butterfly airhorn shaft that the tube sits under, on one side only. The other side i left as it is. Basically I took about the width of my thumb and half of the diameter of the shaft off just above the tube. I have many spares so i can go back to untouched shaft if need be. Im going try shaft grind , compare to no grind, Then shorter tube on grinded shaft. And shorter tube on no grind shaft. I may end up with the shop vac straight to the carb if its not strong enough to pull through the intake. I will be looking at pattern of spray, and how long it takes to drain the float bowl. Im thinking which ever way drains the bowl the fastest will probably be the best.
I hope those little sparkles from your vac electric engine won't ignite mixture...:error: But what do i know... Peace,
Agreed, I'd try it with an isolated air suction source, like over a big sealed barrel with the air being drafted out from the side so the fuel lands at the bottom and not sucked out the vac. You could probably start with a less flammable fluid (diesel fuel) to get close before switching to actual gas. Is there anything with the same density as gasoline but less hazardous? Kerosene, paint thinner?
