carb issues (vacuum ports & linkage)

[Archangel]

Yes, this is for my truck, I know it's way offtopic in a Ford-specific tech forum, but I hope the same carb is used on some Ford vehicles and someone will have experience with it, if a moderator feels the thread don't belong here please move it to where you find suitable. I also don't know what type of carb this is, hopefully someone will recognize it.

Anyways, here's the deal - truck ain't idling right and also tries to die when going in gear unless I give it some gas. After taking the air filter off and looking at it I suspect it's the carb giving me hard time and I got some questions about it:







In the pictures above there are some vacuum ports that I've circled in bright green, those were all capped off but the caps were cracked and were not sealing - what are these ports used for, and shall I cap them off again, or shall I connect them to something?

Another set of questions pertains to the carb's linkage - the things I've circled in blued, it looks like there needs to be something connected there, but there isn't. Moreover the first set of flaps (I assume those are the primary butterflies) aren't connected to anything and their weight defaults them to wide open all the time - if I am correct that means that at idle the truck is running very very lean which would explain why it has no guts and I have to give it gas to keep it running. The seconady butterflies (the bigger set of flaps, in the rear half of the carb) seem to be connected to only a vacuum solenoid, which is connected in such a way as to close them or prevent them from opening - makes sense, kinda, but then what makes the secondaries open? I've never worked on a carb before, so I'm just running on observation skills & common sense here... HEEEELP!!!

[turbo2256b]

HAS THE TRUCK BEEN SITTING?

[Archangel]

HAS THE TRUCK BEEN SITTING?

Yeah, most of the last few months, previous owner parked it right after he suspected something's wrong with it, but between losing his job and working on his and his girlfriend's bikes (croch rockets) never got around to actually looking into it or fixing it up. I only drove it 10 miles to home, then parked it and it hasn't been moved or even started up since then. Why?

[Archangel]

Carb is a QuadraJet, and here are pics of its driver side and top side:





QuadraJet carbs were used in some Ford vehicles, weren't they? What is everyone's opinion on them? What is involved in rebuilding a QuadraJet? Alternatively, what is a good 4-barrel carb that can replace them?

[grandpaslincoln]

In the first pic, that big nipple looks like a fuel bowl vent, the other nipple looks like a ported vac. In the second pic the nipple circled green is for the choke diaphragm. The one that's next to the water neck is a heat controlled vacuum valve. As for the linkage, looks like your missing some of the linkage that controls the choke. As far as everything else, I'm not sure on. I'd also get some valve covers on that, or at least cover up the heads to keep debris and shit from getting down in the oil return passages.

[Archangel]

In the first pic, that big nipple looks like a fuel bowl vent, the other nipple looks like a ported vac. In the second pic the nipple circled green is for the choke diaphragm. The one that's next to the water neck is a heat controlled vacuum valve. As for the linkage, looks like your missing some of the linkage that controls the choke. As far as everything else, I'm not sure on. I'd also get some valve covers on that, or at least cover up the heads to keep debris and shit from getting down in the oil return passages.

GL, so I keep the big port on the front open, and plug the small one? The port off to the passenger side (green in second pic) was capped off, the vacuum solenoid you're talking about is actually hooked up to the same T-ee port where the distributor vac advance goes to (you can see the hose in all first three pics, it's the very short one), and it actually only operates the rear flapper (choke?). Also the whole choke setup is kinda weird, the vac solenoid actually closes the rear flapper (choke), what opens the flapper is unknown to me just yet. The linkage for the front flapper (choke) is missing, so I got no clue where it connects or how it operates.

Oh, and the valve covers are currently getting the flanges straightened and flattened, tomorrow I'll try to get some steel core gaskets and set the valvelash before I close the heads. Also there will be cast aluminum VCs coming in, just need to find a good deal on them on Ebay.

[grandpaslincoln]

You can leave the big port open if you wish, I plugged mine with a cap to keep dust and stuff from getting into the bowl. Plug the small one as well, unless you want to hook it to something. Then you could recap all the ones that were capped before with new caps, that should solve some of the problems. You should verify your idle speed as well, it may be dropping too low when you put it into gear and it dies.

[Archangel]

Thanks GL, I'll cap them all off too, just to be on the safe side. My idle speed when cold is as of right now unknown cause the engine keeps dying. When warm it races at 1000rpms, it was lower than that but I bumped it up a little to help idle in gear, it actually worked. Of course all my idle problems might have been due to the all the vacuum ports being open, will see how it acts when they are all capped off, the valvelash is set properly, and there is fresh oil in the engine.

[turbo2256b]

i have rebuilt a lot of them quadrajets.

[gadget73]

Is the choke pulloff connected? Looks like there is the short rubber hose connected from the carb going to the general area of the choke pulloff, but it looks almost like the nipple on the pulloff itself is unhooked. What does your distributor connect to? Should be ported vacuum. PCV will go to one of the large connectors down low on the carb body, and for the most part you dont need the rest. Probably it was for emissions stuff that was removed at some point. The fuel bowl vent would be included in that. Q-jets are OK if they work. If they haven't sat around forever and are still basicly functional, they can be rebuilt without much trouble. They're decent carbs, and run pretty darn well as long as they aren't screwed up.

[Archangel]

Is the choke pulloff connected? Looks like there is the short rubber hose connected from the carb going to the general area of the choke pulloff, but it looks almost like the nipple on the pulloff itself is unhooked. What does your distributor connect to? Should be ported vacuum.

The secondary choke pull-off is hooked up exactly to the short hose you see, that hose and the one for the distributor advance both hook up to the same T-ee vacuum port.

PCV will go to one of the large connectors down low on the carb body, and for the most part you dont need the rest. Probably it was for emissions stuff that was removed at some point. The fuel bowl vent would be included in that. Q-jets are OK if they work. If they haven't sat around forever and are still basicly functional, they can be rebuilt without much trouble. They're decent carbs, and run pretty darn well as long as they aren't screwed up.

Well, it was pulling pretty strong at 55mph and over 3500rpms in 2nd, apparently running on 6 cylinders leaking oil all over the place that is It's just the idle and low rpms that are messing up for now, but I'll look into that when I get the ports capped off and the VC back on so I can fire it up again.

Oh, what are good sparkplugs for a 350 SBC?

[Archangel]

i have rebuilt a lot of them quadrajets.

Kinda expected that I'll bring it over to you to have a look at it once I get it running halfway decently and also get some insurance so cops don't bother me. By the way, are you staying in MI, or are you moving?

[gadget73]

Oh, what are good sparkplugs for a 350 SBC?

AC Delco R45t or R45ts is typical depending on the head. Pull one of the existing plugs and cross it over. I forget which is which, but one of those plugs is a long reach with some goofy long threads on it, the other has short threads. I also have run NGK plugs in Chevy motors with no complaints, and right now my truck has Autolites because the parts store had either cheapo Autolite, Bosch platinum which I determined to run poorly in this motor, or some expensive double platinum $6 per plug AC Delco thing.

[turbo2256b]

Kinda expected that I'll bring it over to you to have a look at it once I get it running halfway decently and also get some insurance so cops don't bother me. By the way, are you staying in MI, or are you moving?

You could just bring the carb if you want. Used to have a couple of them around here from boats. That big flapper is the air valve for the secondars not a choke. The little vacuum can with the short hose keeps the air valve closed when the choke is on.

The big issue with those caarbs is if some little cup plugs start leaking inside the carb. Other than that there fairly fool proof. Rebuild kits are fairly cheep if you want to go that route.

[turbo2256b]

Post 4 blue circle not shure of what your circling but I think you have circled the rear barrel metering rods and linkage it lifts the rods out of the main jets when the air valve opens.

They were used on some of the 460 series engines and some 351Cs I believe. Holley makes two sizes of Quadrajet replacements.