I should also note it’s impossible to not block the power valve circuitry as this carburetor sits if I’m to drill into the side.
Personally I think I could avoid drilling into the side and instead drill opposite of the float bowl but then it could get in the way of my throttle linkage.
Pointing with the straw is the Power Valve air circuit which detects lower vacuum. Vacuum holds the valve rod up and when you’re at full throttle the rod goes down and opens up the power valve.
I think I don’t need it. Especially considering the secondary wouldn’t be for woodgas anymore.
Consensus: Power Valve Not Necessary!
With proper jet tuning you don’t need that enrichment system, it was made for defeating emissions regulations at idle and low throttle.
@TLC didn’t you say you have a Weber on your car? I will make sure to document this for you.
Modifying this Weber will be for the Mazda, I’m only posting it here for now. When I modify it properly I’ll make a separate topic. But it’s for the same reason I modified the Quadrajet, having my primary be for gasoline and secondary for woodgas, using two throttles but this one is for the Mazda.
I think this will be very handy for people that have the Inline 6 cylinder engines and under, anything bigger than 250 cubic inches you’d want the QJet. Luckily you can buy cheap chinese clones of both of these carburetors. The Weber clones are about 120 bucks, and the QJet clones are roughly 200.
This particular part was me just thinking out loud, Webers have their own special enrichment system to have a lean idle and partial throttle for fuel saving but starts spraying fuel at high throttle. I was worried it was necessary but it’s actually more of a bandaid for poor tuning so with good jetting you don’t need it.
Doing this modification to either the Weber or Quadrajet means you don’t have to worry about soot clogging up gasoline jets, so if you have a failure with your gasifier or run out of wood, you aren’t limping home with a clogged carburetor.
Edit: Mother Earth News used this 2bbl conversion on their 250 cubic inch I6 engine powered sawmill, I’m amazed by that since the woodgas feed pipe is only 1.25".
Ok see what you are working at improving, that 1-1/4’ pipe do seem small,maybe for generator that don’t need much extra power, my dad used to have a 292 strait 6 in his race car, 66 chevelle- it had lots of power with a 4 barrel intake, he must have sold that one years back in the 80,s. Have some good local track roundy rounds fun though.
Is the Webber carb the one with 4 barrels all same size, on the old Chevys.I seen about a 3/4" spacer plate the other day out back like all same size barrels
The Weber is only a 2 barrel, 32mm primary and 36mm secondary. It’s a progressive 2 barrel.
Holley had a license to make these it’s called a Holley 5200. Motorcraft/FoMoCo also had a clone for their Pintos.
But there’s two different kinds of Weber 2bbl, clockwise and counterclockwise. Mine is the DGEV counterclockwise electric choke, Pintos used the DFAV the clockwise water temp choke.
Modification should work for either one.
There’s also the big brother Weber the 38/38, bigger barrels maybe better for something in the 250cui range.
With my Mazda I don’t think I’m gonna have any problems. On charcoal gas I ran it straight through both barrels and even then I didn’t get much more acceleration with both throttles open. On gasoline I barely ever had my foot to the floor, secondary don’t open until about 3/4 throttle normally.
Yeah you plug the jets going to secondary on either carburetor, it’ll no longer have gasoline running through it. JB Weld Gas Tank repair putty works good for that, it’s like plumber’s epoxy putty.
If @Norman89 has a spread bore intake for his 350 I’d be more than happy to make another one of these QJet carbs just so I have an excuse to make another one for a video.
I keep looking at the Quadrajet and I think there’s a way I could put in a double woodgas intake, one pipe per side of the secondary in the 4bbl. There’s zero air circuitry in the back of a Rochester.
I think with this paycheck I’m gonna buy a bigger drill press so I can drill out the holes more cleanly. My little desktop is too small for the job and I had to meticulously drill out the back with a handheld drill and hole saw bit.
THAT sounds like my heat exchanger inlet air pipe, i allmost could not get it from the frame rails and cramed up too close to the clean out fitting on my burn tube exit pipe too the heat exchanger-I loose a little heat before it gets too the heat exchanger- but should be fine other than i probbly
picked up another 50 pounds or so.
Got the QJet on the truck, forgot to do one thing.
I forgot to remove the old secondary throttle mechanism which is actually a sort of one way bearing. Right now the truck is sucking open the secondary butterflies to achieve higher idle. Going to need to take that off and make it a fixed throttle. It’s basically making it’s own air leak right now.
I was thinking of using rod linkage for the woodgas throttle using the column shift, but I can’t remember the name for a pivot point that rotates the linear direction.
Right now the shift column lever moves side to side, from Driver to Passenger, but the secondary has a backwards and forwards direction, from the front to the back of the truck.
Seems like it should work plenty good after the mods-- more to them quaderjet carbs than i really noticed- it will be interesting seeing it hooked too wood gas and gasoline on stand by,!
Thanks Cody. This will be very interesting. I am busy changing from Weber to the original SU carb system as the consensus is the Weber is too small for my set up and that’s why my fuel consumption is so high. I should be getting about 8km/ltr with the SU’s and not the current 3.5 km/ltr that I am getting with the Weber.
Got my woodgas throttle JB welded to the butterfly shaft. Waiting on that to cure.
I found a way to utilize the old shift linkage arm to operate the throttle. I used a 5/16" bolt and a very large washer with a hole big enough to use choke cable. The washer is slightly loose so it can move on the bolt. As the shift arm goes down it will pull the throttle open. I’m using a small pull spring as my return, so with the spring assisting that should get the cable returning just fine.
I’ll take pictures tomorrow after the JB weld has cured enough. It’s pretty simple honestly.
I need to make sure my gasoline side of things is still okay, need to cap off the woodgas inlet to do that, even with the throttle closed it’s sucking in air. I’m not that surprised by that, all throttles let a little air pass through. Last time I tested, it would run super lean at first and then start climbing in RPM to ridiculous levels if I enriched the mixture screws. Almost runaway levels.
