I have a SB with Quadrajet in my 49 Chevy PU. The motor and running gear were out of a 74 Camaro. I am pretty sure the needle valve in the float is stuck because I'm not getting any fuel in the intakes and I am wondering if there is any way to unstick the needle valve without disassembling the carb. There is fuel in the tank. The fuel pump pushes gas to the carb. The fuel filter is not clogged and I even tried without the filter and still couldn't get gas to the intakes. If I dribble a bit of gas in the intakes it fires right up until the fuel is burned. I tried squirting some Kroil into a few passages, tapping the carb lightly, and blowing a little air into a few passages with no luck. Any suggestions?
If the needle valve is stuck there is probably a reason. It could just be varnished up and stuck from sitting, not sure if there is a good way to free it up without taking it apart though
When you mention the fuel filter, do you mean the one that is in the carb, behind the inlet nut? Or one that is in line before the carb? Since it sounds like you are a bit wary of taking the carb apart, be sure to find a good instruction manual before you start. There are some tricks to doing it, so you don't have problems. But yeah, you're probably going to have to take the carb apart, clean it, and put some new parts in. It can be tricky the first few times you do a Quadrajet, so do your homework first, so you don't screw anything up. (and at this point, don't get too excited about having to bush the throttle shafts or anything like that--just stick to the basics)
Fill the carburetor bowl through the bowl vent with fresh gasoline, and leave it for 24 hours. Start the vehicle, if the float was stuck from varnish, when the float tries to fall, it may break it loose. Jon.
I have unstuck needle valves in carbs with air hose in the fuel inlet. It works, but does have its dangers. I usually try blowing close to the inlet first. Then if that doesn’t work I try to seal it. Bones
I like this idea! But I think I would modify the idea by machining a fitting with end that would screw into the fuel inlet fitting, and the other end with a tire valve. That way I could apply pressure slowly through the tire valve. Jon.
Still wondering what it might look like inside the bowl, if the needle is stuck. When was the last time it was running? I would advise a look /see inside.
What Carb King said....easy to put good gas in from the top opening.....maybe a little Berryman's in as well.
I'm thinking that filling the bowl through the vent might be easier said than done here. It's the 3/8 " tube in the middle of the carb. Filling the bowl might work . Kroil? Doubtful . Might try a piece of 3/8 flared tube , threaded into the front of the carb, bent up in the air. Fill it with good ol' W/M $1.97 carb cleaner. If it's empty the next day, maybe you got lucky.
Might sound a little odd but I have had success freeing a stuck float numerous times by just gently tapping the side of the bowel with a wrench, ratchet etc, just gentle, sometimes it just pops free. You can also use some vacuum or fuel hose that fits snug over the bowl vent and a funnel to get fuel into just the float bowl and not everywhere else. GL Cheers
Fill the bowl thru the vent like Jon said.. Make sure you let it sit for awhile to loosen things up.. I have had good results doing it the way GL said.. If you take the air horn off the quadrajet make sure you remove the two screws down inside the barrels. It should come loose with a slight tap or even better a little prying.
Don't be afraid to take the top section off for a look. If the old gasket cracks on ya, gently save it to compare with a new one. In a pinch, I have soaked old gaskets for a couple of hours in a mix of leather conditioner and warm water to plump 'em up and get some life back in them. Just give it a brief rinse and blot with paper towels. Lifting the top off and later replacing it is pretty intuitive. There's a link or two to disconnect and later re-connect in reverse order. Pay attention to which way they orient. The secondary metering rods are very loose so when you are gripping the top section, reserve your index and middle fingers to rest on the top hooks of the rods. Easy-peasy. These are old recollections so just eat the meat and throw away any bones when you follow my advice.
BUMP!!!!! Is there something that keeps the secondaries (the butterflies not the plate on top) from opening all the way, maybe until it's warmed up? When I open the primaries all the way the secondaries are only about half open. I can push them fully open but I don't see anything on the choke side prohibiting it.
I think the secondaries respond to the carb's demand for air. When there is enough demand under load, the secondaries will open. I don't think secondaries will open when the engine is not running and you crank the throttle linkage.
That is for the vacuum operated flap on top. I think I figured it out, there are two springs on the secondary buttefly shaft, it takes a pretty good pull to open them all the way. I think I just wasn't leadfooting it enough! Going out for a test, hide the women and children.
And , once again , no update , I love helping people who don't have enough manners to say ( at the least,) thanks
Guess you'll have to settle for my update. I figured it out. There are 3 holes you can put the throttle cable pivot in. It was in the rearmost, almost vertical to the shaft and 90 degrees to the cable. So at full throttle the cable was pulling backwards as much as rotating the throttle shaft. I move it to the forward most hole, problem solved. Thanks guys.
The top of the Q jet is pretty easy to remove by itself. I would at least pull the top and check the condition inside the bowl. Put some chapstick on any gaskets you replace and they will come apart much easier next time.
Neighbor and his son were working on an old tractor. They were having carb problems. Father calls me over to look at it and we find that the brass float was completely deformed. They figured there must have been a ton of water in the bowl, the water froze and crushed the float. I forget the exact details (this happened several years ago) but it was later determined this could not have been the case. I then asked "did you blow out the carb with compressed air" and the answer was "yes". I believe the son blasted a ton of air in through the fuel inlet, the float rose, the needle valve seated and the immense air pressure (rookie move) in the carb crushed the float. Once I explained this to the father, he was in total agreement. Not saying your Quadrajet has a brass float (not saying it doesn't) but be careful you don't blast too much air through it ... just sayin'
There were some hollow plastic and even some brass floats available at one time...Maybe Balkamp ? The brass ones were physically smaller, and supposedly the hot set-up for race carbs, allowing the bowl to hold more fuel.
There used to be an American supplier of several different brass floats for Q-Jets (earlier ones). When I was still restoring carbs, I used the brass ones exclusively after failure of genuine GM floats, sometimes within a few weeks. Problems solved. Supplier no longer has them, but still has the tooling, but requires a 1000 piece minimum to make a run. Mark - impossible to press the brass in as intricate a form as the molded foam. The difference in fuel volume in the bowl was small. Jon
The plastic floats in time will fail. Remove the float and place it in a container with gas in it to see if it floats or sinks - do not use water because a defective one will still float. Ethanol in the fuel may be a factor. Have used new floats with no issues. Hope this helps.
Mark - I do know a few NHRA folks, and a lot more circle track folks. Over the years, have built a few carbs for NHRA folks (mostly genuine Carter AFB, and a few TQ's). There was also the occasional Q-Jet, mostly in the 1960's. And then a youngster by the name of Cliff came along, and there was no need for me to continue to do Q-Jets. We did more Rochester 2G series for the circle racers than carbs for drag racing. The above is just background. Every racer is also a highly educated mechanical engineer! This comment, while in jest, is not meant to be mean, rather a comment on the racer's willingness to try changes, often ignoring the Law of Unintended Consequences. There are many "tricks" one can do to the Q-Jet; and some that folks swear by simply make things worse! The "tricks" for the Rochester 2G series are even more interesting. We used to "undo" the "standard" modifications for the 2G done by the racers, and lower their circuit times! Actually, we threw away the carbs they had modified and started with unmodified carbs. The Q-Jet mods are borderline OT for this forum, as the first Q-Jet was introduced in 1965. The Rochester "G" series (2G, 4G) are much more relative, as the 4G was introduced in 1952, and the 2G in 1955. And of course Carter introduced the AFB in 1957. The TQ was 1969, so definitely OT other than a mention in passing. Anyone wishing to discuss mods for the OT Q-Jets, and TQ's (up to and including 1974) please call 573-392-7378 (9-12, 1-4 Mon-Tues central time). I really do respect Ryan's policies. Jon.
Not real close to AZ in Huntington Beach Ca. SMI Sean Murphy Induction has been one of the experts with Quadrajets especially with NHRA competitors for years. He has a website you can check out. He has built many carbs for friends and me for LSR, street, and Circle track also. He has a great reputation.
Jon, Some of the guys try tuning a Qjet on the dyno...Almost never works, where they have to lean it out at the track especially around Indy...They just won't leave the line worth a damn in real world , track testing. I always tune by the time slip . 60' and mph numbers don't lie or fool anybody. (below is just background) I didn't write the book on Rochesters, but I AM in the book. (Doug Roe Rochester book, first printing) ;-)
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