How to understand and diagnose Quadrajet secondary problems
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- Опубліковано 7 вер 2024
- If your Quadrajet has no functioning secondaries, or runs poorly when the secondaries are engaged, this video will help explain how to understand and fix those problems.
Great video. I just put on a rebuilt quadrajet. Worked great at idle, set primaries to maximum vacuum, drove thru town, working beautifully. Got outta town and stomped, sounded horrible all throughout WOT. Spent hours setting secondary airflow, pulled it off once. Still sounded like he'll. Then watched your video on those tubes in the secondaries. Might be another day or two, but that's gotta be the problem. THANKS
These videos have been very helpful. I did the unthinkable and fit a quadrajet (81-86 year) onto a Ford 390. Some call it sacrilege but I think the quadrajet is the most efficient carb out there. I completely rebuilt it because the bowl was rather dirty. It runs great. Just disappointed in the mileage because it's actually getting worse gas mileage than the new edelbrock I had on it before this. It's been fun to tinker with it, though. It starts right up warm without having to hit the gas pedal while cranking. I think I jetted it right. The primary metering rods are a 51M and I just guessed and used a 77 jet. The 72 jets that were in it before I rebuilt the carb were too lean. It seems to run fine and I get a nice brown color on the spark plug tips. Watching your vids helped me fix the secondaries. The top flap springs were just a little loose. And you're exactly right; once you rebuild them, they aren't that hard to do. You just gotta make sure to hold the primary meter rods in the holes and hold accelerator pump rod down while putting on the airhorn. It's a bit of a pill to get those primary rods in the holes, though. I just pulled a different one apart a few weeks ago and somebody got impatient and just rammed the horn on. They bent one primary meter rod and J- hooked the ends on both. Thankfully I had a parts donor, albeit they are the newer 51M and not the 49. The inside was pretty corroded so it needs serious cleaning. The power plunger was seized in its bore pretty badly as well. Glad I didn't try to just slap that one on and run it.
Damn good video. I have one on my square body 454 pickup. For years, and just recently, friends have told me the best way to fix my Quadrajet was to replace it with a Holley - and then they giggle. I know almost nothing about these carbs but after seeing this and a few of your other videos I'm fairly certain I know more than they do.
I find that most people are quick to bitch about anything they don't understand. I'm no genius but have learned over the years that anything can be a pain in the ass until it is understood.
His seminars are worth reviewing in full! His knowledge only comes from years of experience and experimentation with carbs.... it's such good information.... why is it most individuals will start poking around with the carburetor first when they have a timing issue or bad fuel pump? Once they have they've blown off a perfect factory setting.... Thanks for the help! Sincerely, JD
I have learned more in one hour and now I have an understanding of what I need to make my GM 455cc run again. I am going to power watch your videos and gather a bit more information. I am determined to make this motor run again and I think with your help and video instruction I just might do that. Thank you for sharing your knowledge and experience with us. I am going to sign up and follow and share and comment as I go through this journey to make this big block engine come to life. You are easy to listen to and you explain things that are both informative and entertaining. My father used to say that same expression "For S**T and giggles" to me that is how I talk to my children and grandchildren. Even when I get my hand slapped for doing so.
Tyler, your quadrajet videos are always very informative. If you are like me we would be rich if we had a dollar for everytime someone bad mouthed a quadrajet but they are probably the best designed carburetor ever built. They will give pretty good gas mileage as long as you keep your foot out of the secondaries but still give performance when you need it.
very well done and slow and good to learn with this speaker
Thanks for these videos. A full understand on how something works is the first step is fixing things that go wrong.
Fantastic video! I'm sitting in front of a qjet right now I have to rebuild. I'm running a 2bbl Holley right now and can't wait to get this Carter on. I watched your video with my '77 4bbl in my lap. Thanks so much!!!!
Thanks for taking the time out and explaining this carb
can't find a way to email you directly to thank you. quadrabogger no more! I just rebuilt two 1708 qj using your videos as reference and wow...just wow. my trucks are alive again. I'm a Bama boy also
great video, gonna see if i can get these secondaries working now
Very informative! Used this video to check and make sure my secondaries were operating correctly. All good!
+maxpayne4x4 Thanks!
+WhoSaidTyler yessir!
I know the secondary's wont open until under load. Is there a way to check that without using a camera? I'm not sure if mine are working properly.
I bought a rebuild manual from a guy named Doug Roe when I was twenty years younger. He worked for the Rochester quadrajet company and I can assure you that the man was a guru with these carburators! I highly recommend that if you want to understand thoroughly about a quadrajet that it's a must have! ( Or what I refer to as The Bible.) What I have learned the issue with the quadrajet is the foot that is punching the damn gas pedal! Most idiots that I have dealt with think they can mash the pedal to the floor instantly expecting their hunk of shit to react like a top fuel funny car! I always have to reprogram the way they are thinking and what they are expecting of the carburetor. If you don't have some money in good pieces in your engine then don't expect neck snapping power just because you just had the carburetor rebuilt! It was designed as a drive ability carburetor! But don't under estimate this spread bore design! Even Holly made some spread bore carburetors for a few badass engines that chevrolet! Put in their rides!😉
Thank you, i have it.
Gee, officer, I was just checking to see if my secondaries were "engaging". It's one of my favorite sounds in life is hearing a spreadbore kicking open with the aircleaner lid flipped over.
Grant W. Whitwam be careful ya might suck the hood down and cave it in
Wow, that's weird. Just yesterday i was "testing" my secondaries on some back roads after adjusting them per Tyler's other secondary video. Of course the speed limit was exceeded and this very thought came into my mind. I'm bound to tell the truth so yep, "Officer, I just adjusted my secondaries and was testing them".
Awesome video very informative
Fantastic info Tyler….got a c10 here in England UK…..parts and info on them is as rare as rockin horse shit here so your vids are much appreciated…..you da man!!!! 👍👍🇬🇧🇬🇧🇬🇧🇺🇸🇺🇸🇺🇸
awesome, thank you.
#3 Parts to a Quadrajet those are the top ,#1airhorn #2body, #3 base, that way you can explain to whomever your speaking to knows what you're saying.
Great vid Tyler! Best Q-Jet walkthrough ever. Thank you!
Hello I have a 7028210 Rochester that I have rebuilt. On the Air Horn there is no secondary discharge tubes installed in bores.
Also there is no cross holes drilled into Air Horn for the fuel to come out. Have you ever seen one like this or did the factory make a mistake in manufacturing. If so I guess I will need to drill them.
Good Q-Jet video.
you ought to be building custom, handcrafted made to order rebuilt QuadraJets....I've always loved them, in fact I just removed a Holley Sniper EFI, and re-installed the QuadraJet on my 454...
Do all 73 and up have the front choke pulloff? Mine is missing on mine. I see quadrajets for sale without them, new and rebuilt!
Great video. Is it safe to take the air horn off the carb while the carb is still mounted on the engine to check if the secondary tubes are attached? or is that just looking for trouble and the whole carb should be taken off the engine? wondering about the risk of something falling into the engine if it is done while on the carb is attached to the engine.
What purpose and function does the accelerator pump serve?What symptoms will be present for accelerator pump issues?
mechman4 the accelerator pump serves to squirt extra fuel into the venturi during the start of acceration.
When the throttle is opened up the vacuum across the venturi suddenly decreases causing fuel starvation when the engine needs fuel the most. The accelerator pump delivers fuel during this vacuum intermittency.
Sweet! I've been waiting for you to post a Quadrajet video for a long time, haha.
thanks great video
hey tyler! my 4mv idle drops after i drive. It starts good,idles goods, runs good. But then i drive then turn it off, when i start it back the idle drops really low. Your thoughts?
What is the new gold vacume on the side that why my 2 other barrels wont open i push it in and it it barely moves i think it has no vacuum i a a 403 ci in a 81 cutlass its the fa version 403 thats built better it take iff roasting te tires on 2nbarrels i can only imagine hiw much hp ima gain with the full 4 barrel what be a good carb to just replace with a new carb? If i manually hold the side pieces i can force the 4 barell to open my barrels dont open butteryflys i have to hold them open buy hand
Hi, I have a 1984 C10 305 V8 Original, Cast Iron Intake, Electric choke, small metal line comes off the exhaust below the exhaust manifold for helping warm up engine( when cold closes when hot opens) works off vacuum on exhaust on passenger side. Has EGR Valve on cast Iron intake, but I have Removed smog control. Will it be safe or important to close off the heat cross over on this cast iron intake before reinstalling? Will this help the carb be cooler and run better. Thanks for info
It won't make it run better, at least not in the winter. The heat helps atomize the fuel, although by now the passage is likely plugged with carbon anyway.
Hi Tyler great video!!! I have a 5.7L 350, just starting to trouble shoot cause I cant pass smog in CA. I noticed that my secondary air valves don't open. Do I have to floor it to get them to open or is the engine so small that they will never really get used.
the engine has to be under a load to open
I have a question for this carburetor the jets is not working but the engine is like full throttle when is running can't kick it down so I wonder if you ran to that problem before?
awesome video
I have this carburetor on my boat and recently when I release the throttle to neutral, the secondary doesn’t close all the way making it so I have to shut my ignition off, go back to the motor and manually close the secondary. Any ideas what I should look for? It’s a 1985 Volvo motor with the quadrajet carb. I can’t really figure out why it’s not closing.
Tighten the screw on the side of the arm that pulls them back.
Tyler. I just bought a QJ for a 455 that was rebuilt. Runs well, except, when I punch it, it hauls butt then slows. Should I adjust my float bowls?
Sound like it or maybe just fuel filter
Great video. I have 2 q-jets that were rebuilt by national carburetor. I order them with electric chokes. The mechanic I paid to install them said that the chokes were not necessary in CA and did not hook them up. My secondaries will not open, is that possibly related to the chokes not being powered? The boat runs great up to about 3000 RPMs and any throttle past that makes it run poor. The chokes are currently adjusted open as much as possible. I can’t find anyone who will work on this boat at this point due too it’s size so I am on my own.
the choke controls the little stopper, he explains this in the beginning of the video
its been 5 months, hope ya got it figured out. I'm CA also i have my choke wired open...still trying to figure out why mine still isn't opening...
Hey bud I inharited up an 82 Chevrolet 5.7 pickup a couple years ago, that only had 28,000 origonal miles it was my grandmothers. It was left to set for about 10 years so the first thing i did was to replace all the vacume hoses and rebuild the carb. the mice had a hell of a nest in the air cleaner. I have rebuilt probably 50 of these carburetors and never had issue till this one. It has the automatic part throttle and i forgot to count my turns on it when disassembling it. i started at 2 1/2 turns and have fiddle fucked around with it off and on and still have a stumble when i smash it... after a second the rear end breaks loose and it accelerates fine. any help will be appreciated. Thank you, Jack
+J.W. Hunt That's probably not the adjustable part throttle causing that. The APT simply tunes the mixture at part throttle, as when you are running along at 60mph or so. You can fine tune that by reading your plugs after adjusting, or lean it until you start to get a slight surge, then go back rich until it goes away.
The stumble could very well be some varnish or debris in the secondary of primary enrichment system I showed. Also,make sure the secondary air doors are adjusted right. Good luck, man.
7:00 you're welcome.
Awesome vid!
My quadrojet on my mercruiser is shooting fuel up through the two spouts after running for about 8 seconds is there a simple fix for this?
It needs overhauled with a new float and inlet needle. You can probably tap it and make it unstick but it WILL happen again and you do not need that on an inboard.
People don't understand that they are way better than any holley or edelbrock carb period fuel milage and the secondaries opening give a kick like no other carb gm and Rochester put a lot of engineering in them for a reason they are more dependable and just are better all around try putting a 750 or 800 on a 305 and see how it runs w a holley those will run on any engine I have done it and it performed flawlessly
Can you do a M4ME video I have electrical connections I'm not sure of
Heat soak my 1972 dark never had it but my 1987 d150 has it .
My q-jet taking off or up a hill acts like it's out of fuel
38:40 wow a quadrajet secondary literally works like a toilet ... nice
Oh God..lmao..lol.."some force"!!!!he says the guys have to tighten the shit out those bolt cuz of some force that's gonna gettem!!!
Clarify how to identify 750 CFM and 800 CFM ,I am confused.
Take a light and look down the primary(front) venturi. About halfway down there is a "ring" cast into each venturi. On a 750 cfm, it's just that, a solid ring. On an 800 cfm, there is no ring there, just two small "baby bumps" on each side. So, look for either a ring or baby bumps and that will identify which you have.
perfect sleep video ... well guys the other video .. we'll get into that later .. the deal is .. you know .. you know ...
We got the same flashlight.
MrFang333333 good 'ol harbor freight!!!!
zzzzzzzzzzzzzzz
Easy fix. Throw it in the garbage and buy a holly
Great vid !