Quadrajet Power - Quadrajet idle circuits explained

Quadrajet Idle circuit, main circuit and secondary circuit. Emphasis on idle circuit to help with idle issues.
These carbs need internal modifications to idle correctly when engine is modified with higher lift cam and higher compression. Idle tubes, down channel restrictions and other components need to be modified and then the Quadrajet will idle correctly and deliver the power.
www.quadrajetpower.com
Parts featured in this video
IPT, Idle pickup tubes bit.ly/35Zxic2
DCR, Down channel restrictions bit.ly/33FlbhI
BITPACK, precision drill bit set bit.ly/35WoP9F
New Jets: quadrajetpower.com/jets/
New Primary Rods: quadrajetpower.com/primary-rods/
New Secondary Rods: quadrajetpower.com/secondary-...

[@bobdixon4998]

Your videos are great. I wondered if you could do a video about loss of vacuum in an old carburetor/ vacuum system and how that affects the vacuum advance ignition /carburetion ratios. At start up,the ratios between the choke, fast idle and vacuum advance, and which to tune first. Then to a warm engine and the curb idle adjustment. This is a really cool subject. Keep on, I'm learning a lot. All of the guys who are sweating over their own projects and their friends projects appreciate you very much. Thank You.

[@tmx63]

Great channel. A properly-tuned Q-jet is, imo, the best street carb ever made.

[@b.s.adventures9421]

Great detail. Very helpful on just understanding how this all works.

[@shock-eh3849]

GREAT VIDEO. CLIFF RUGGLES BOOK WAS GREAT AND SEEING THIS VIDEO HELPS EVEN MORE. THANKS

[@angry3055]

Great info, i resolved my issue by restricting the idle bypass hole air my mild BBC. The bypass holes were too big for my application, causing the idle mixtures not to respond very well at idle.

[@george1la]

Between Ruggles book and your videos I am starting to understand how it works and how to fix my problem in the going off idle circuit. I have to richen up the idle circuit. My tubes are stuck pretty tight. I have to try to get them out again or try to drill them from the top and flush out any chips.

[@BruceLee-df5ml]

Great video this might help smooth out my idle with the thumper cam.

[@lionlocks5910]

Thank you for your videos. I will always buy from you guys

[@pjmccoy4216]

Another great video. Thanks.

[@QuadrajetPowerLLC]

Glad you enjoyed it

[@shortgeorge8272]

Thank God for your tutorials, wish I had watched these before I replaced my accelerator pump then installed new gaskets... now it surges at idol...

[@danlaabs5090]

Great video!

[@onsturn]

Great info thx! I’d like to know more about all the different secondary hangers and why I’d have one over the other.

[@kevinclancy.]

facinating videos thanks I'm learning so much. when you say you get a nozzle drip on the primary side, how could one tell? could that be creating raw fuel puddling on the intake manifold plenum? I had to do exactly what you said- crank the idle speed way up with the fast idle solenoid to compensate my bone stock 73 quadrajet on a hot rod 350 with big cam and compression. Can't wait to redo the idle circuit like you describe!

[@piotrpierozek2839]

Great videos. Can You explain fuel circuit, how it is controlled when on idle what is holding the fuel from part throttle and secondary fuel cuirciut from flooding the engine, can You explain what is triggering part throttle system to get in and same for secondaries. Air flaps and linkeages are visible but ilustration what is happening with fuel i think can be interesting and big step for understanding.

[@RattleTrapGarage]

Hey just put a quadrajet on my 78 chevy truck starts good but it idels high I lower the idel and then it won't move so I have to turn it up so I can move the truck around

[@nashvilleoutlaw]

Interesting, makes me wonder if a q-jet set up for a big block would work better for a small block with a cam? Wouldn't a big block carb be set up to release more fuel at idle for the same vacuum?

[@bobdixon4998]

Yep they're great. Build it for your application. Get the 850 cfm model and build it for Max fuel (demand) whatever your engine and cam can process in fuel. These guys have a lot of info on volumetric efficiency with these carbs and the applications for them. Let them know what you want, your application.

[@apol55555]

Hello, i have one 81 olds 307 with quadrajet and TH350c gearbox. I have a problem and i hope that with the necessary i will resolve it. The idle screws are scratched with circle scratches and especially for the right one (if you are in-front of the car) it can’t make the mixture and it’s screwed to the end position. So what kind of parts i have to replace, to make it run well? I had replaced all of the gaskets of the carburettor and the O rings. It’s running almost well, but i have a mixture problems with the right side. The lambda sensors (I’m using outside source with a laptop) Sad that the right mixture is too rich of fuel, the sparks coloured confirmed that.

[@georgesabol459]

Hello, very informative. We Pontiac guy's with larger stock cams, also drill a hole in the primary flaps [ shutters ] this seems to work on Pontiac. I will always defer to someone else's expertise. Great video!!!!! With a little patience these carburetors are true performer's. Please think twice before throwing on another brand carburetor.

[@sepasgozar]

Great video👍👍 I really appreciate it. So in another word, we should NOT see any fuel at idle when we look from the top, am I right??

[@QuadrajetPowerLLC]

Correct, fuel should not drip from primaries at idle.

[@Nathan-bz8zt]

Great video!! I'm running a 350 with 2.02 , 1.60 valves and a bigger cam and have been having issues with idle. I'm pulling about 17 inches of vacuum at idle do you think I need bigger idle tubes? Or is this enough vacuum to make the stock ones work properly?

[@BP-ju8bc]

17 inches is about stock. A big cam will go down to 10 inches

[@lennycoluccio9129]

Hi how much for olds 455 one with cam calibration

[@onlyactingup]

Hi Mate That main body seems to be like mine, I need to know more about these two brass screws that sit vertical inside the chamber to the front sides and look like adjustable (flathead blade top) screws. They look like adjustable mixure screws and I have no idea what they are for or do and how to set them. 1976 GMH non APJ 170 number.

[@MySonMarlon]

They keep the Airhorn to the Body with other 7 screws. they are not mixture screws !!!!

[@onlyactingup]

@@MySonMarlon Thanks.

[@johnteague756]

I believe he is asking about the discharge nozzles in the first venturi rings. Those are "brass", and have a screw driver slot with a hole in the middle, but there are no brass screws for holding the air horn to the body.

[@robrobster9148]

Hello, i have a 1969 Riviera with numbers matching engine and carb all stock no modifications. I have set the idle mixture screws and it makes about 19" of vacuum. It runs very smooth. Throttle response is great too. When i am in front of my engine i noticed that the left idle mixture screw did not really effect the vacuum reading. The engine runs perfect. Should i do something about that idle mixture screw? Thank you, Rob

[@QuadrajetPowerLLC]

If it runs perfect, I wouldn’t worry about it.

[@robrobster9148]

@@QuadrajetPowerLLC Thank you.

[@everettpangle1861]

Hello I just put a new carburetor kit in my quadrajet and for some reason I lost vacuum on the tube that pulls vacuum for the timing? What if I used the wrong gasket on the top side would that cause it to happen? Thanks Sir

[@QuadrajetPowerLLC]

You possibly used the incorrect throttle body gasket, between base and body. Order your kit from us and we will get you taken care of. www.quadrajetpower.com

[@ramfootballstud707]

What is your contact info sir?