All Quadrajets to my knowledge use the second restrictor, usually referred to as the down channel restrictor. In order, the idle circuit should go was follows; main fuel well, idle tube, 1st idle air bleed, down channel restrictor, 2nd idle air bleed, transition slot, idle screw. I am still learning, but to the best of my knowledge, the idle tube acts as the jet for the idle circuit. The 1st air bleed is either in the air horn or main body, but always before the down channel restrictor. These two heavily influence the air fuel mixture to the transition slots. The down channel restriction limits the total amount of mixture that the idle circuit can deliver, so that there is a smooth transition from the transition slots to the main circuit. You don't want the transition slots to run out of mixture before the boosters are flowing, or be overlapping the main circuit too much. The DCR also impacts the mixture, but the idle tube and 1st bleed are the means of changing the mix. Next comes the 2nd air bleed. It mixes more air into the idle and transition fuel mix while the throttle blade is below it, and discharges mixture when the throttle is beyond it. The transition slot is like any other transition slot in it's purpose. It distributes the mixture that has been mixed and limited by all of the items before it. The idle screw just gives you the fuel you need when the blades are all the way closed. In my opinion, getting the idle tube, 1st bleed, and DCR in the right relation to each other is the key to a good street driving Quadrajet since most cruising is done while running off the transfer slots.
,,,,,,Notice the float bowl area at video time :07 ; there are two large cavities directly behind the primary venturi bores...There are two vertical casting support ribs seen at the two center bolt holes , by removing these two ribs will add float bowl capacity about 35 percent..........Back in the mid sixties I had a 327 with a Qjet,,,,,,,,I read Car Craft magazine and found some guy that explained this modification he did for his drag car......Can barely recall how I successfully completed this mod on my own carb as [I was young and just starting my tool collection ] ,,,,hell,,I must have drilled a series of small holes in those ribs and filed out the remaining material [ as it was soft] ....never leaked....Most know the Qjet suffered with a small float bowl capacity.........Today I have a small machine shop and decades of experience.....Three garages , .and thousands of nuts ,washers , tools and equipment......welders.......presses......Another area which needs modification is the small Idle Feed Restriction tubes. ; .Feeding more fuel to the mixture screws of the idle circuit and ..Keeping the primaries out of the transfer slots ..Larger idle tubes can be installed to better Throttle response,,,,,etc....
Hi Scott. I have 76 Eldorado with EFI. Its really giving me hard time. I am thinking to remove all injectors and throttle body and put a carburetor. Do I have to replace the in tank manifold as well? Any recs regarding a carburetor choice? Thanks
@@fadilto if you can find a good quadrajet it will fit a stock cast iron carb intake well .... On the fuel pump just use a bypass regulator set for low pressure that the carb needs
I wouldn't trust random Chinese factory workers to make the bore for the power piston the right size, just a thought, I'd definitely be comparing everything to a genuine Q-jet.
The real question is not how close it is to a old quadrajet but does it run properly on a engine .... Plus if you look back at history the Edelbrock quadrajet was Chinese made and in all likelihood that's where they got the information on the carb
Thank you for your knowledge and videos USA 🇺🇸
thanks for sharing your thoughts on this new aluminum qjet
All Quadrajets to my knowledge use the second restrictor, usually referred to as the down channel restrictor. In order, the idle circuit should go was follows; main fuel well, idle tube, 1st idle air bleed, down channel restrictor, 2nd idle air bleed, transition slot, idle screw. I am still learning, but to the best of my knowledge, the idle tube acts as the jet for the idle circuit. The 1st air bleed is either in the air horn or main body, but always before the down channel restrictor. These two heavily influence the air fuel mixture to the transition slots. The down channel restriction limits the total amount of mixture that the idle circuit can deliver, so that there is a smooth transition from the transition slots to the main circuit. You don't want the transition slots to run out of mixture before the boosters are flowing, or be overlapping the main circuit too much. The DCR also impacts the mixture, but the idle tube and 1st bleed are the means of changing the mix. Next comes the 2nd air bleed. It mixes more air into the idle and transition fuel mix while the throttle blade is below it, and discharges mixture when the throttle is beyond it. The transition slot is like any other transition slot in it's purpose. It distributes the mixture that has been mixed and limited by all of the items before it. The idle screw just gives you the fuel you need when the blades are all the way closed. In my opinion, getting the idle tube, 1st bleed, and DCR in the right relation to each other is the key to a good street driving Quadrajet since most cruising is done while running off the transfer slots.
I can seem to find a link to this carburetor, did you happen to have a link or site to go to ? Thank you !
,,,,,,Notice the float bowl area at video time :07 ; there are two large cavities directly behind the primary venturi bores...There are two vertical casting support ribs seen at the two center bolt holes , by removing these two ribs will add float bowl capacity about 35 percent..........Back in the mid sixties I had a 327 with a Qjet,,,,,,,,I read Car Craft magazine and found some guy that explained this modification he did for his drag car......Can barely recall how I successfully completed this mod on my own carb as [I was young and just starting my tool collection ] ,,,,hell,,I must have drilled a series of small holes in those ribs and filed out the remaining material [ as it was soft] ....never leaked....Most know the Qjet suffered with a small float bowl capacity.........Today I have a small machine shop and decades of experience.....Three garages , .and thousands of nuts ,washers , tools and equipment......welders.......presses......Another area which needs modification is the small Idle Feed Restriction tubes. ; .Feeding more fuel to the mixture screws of the idle circuit and ..Keeping the primaries out of the transfer slots ..Larger idle tubes can be installed to better Throttle response,,,,,etc....
Hi Scott. I have 76 Eldorado with EFI. Its really giving me hard time. I am thinking to remove all injectors and throttle body and put a carburetor. Do I have to replace the in tank manifold as well? Any recs regarding a carburetor choice? Thanks
@@fadilto if you can find a good quadrajet it will fit a stock cast iron carb intake well .... On the fuel pump just use a bypass regulator set for low pressure that the carb needs
@@scotthatch4548 thank you. Sorry I meant to say intake manifold not “tank manifold.”
I wouldn't trust random Chinese factory workers to make the bore for the power piston the right size, just a thought, I'd definitely be comparing everything to a genuine Q-jet.
The real question is not how close it is to a old quadrajet but does it run properly on a engine .... Plus if you look back at history the Edelbrock quadrajet was Chinese made and in all likelihood that's where they got the information on the carb
Why not get an original one and rebuild it? Are they getting hard to find?
@@DocZoidberg549 yes ...Cad Co is now out of electric choke cores to rebuild .... Plus at 50 years old even the rebuilt ones have had issues ...
@@scotthatch4548 Crap. I need to start looking asap. I want to build a old school 350.