hello my car had the wrong carb on it, and it sat for 3 years, due to an accident. i bought a rebuilt carb off of ebay and it pre adjusted and i just bolted it on. i havent turned a screw on it, and it seems to work ok except for the vacuum for the AC/heater. now i have the correct carb, but my heater/AC isnt working properly because i dont have enough vacuum coming out of the vacuum canister. i have the vacuum canister connected to the port on the lower rear center of the carb. i hooked a vacuum gauge up to it and it starts off at 0, and works up to 15" after about a minute or so. the amount of vaccuum is low and it doesnt matter if i rev the engine up or not. please note that i have good vacuum on the port on the front of the carb, the one that goes to the thing that sits on the intake and controls the amount of vacuum going to the distributor. the amount of vacuum is even worse on the output side of the vacuum canister. i have one of those vacuum pumps and checked for leaks and didnt find any. so my question is: should the vacuum canister be connected to the rear center port of the carb, and how much vacuum should i measure there with a gauge. is there an adjustment on the carb to increase the vacuum at this port. can you point me in the right direction ?? thanks for reading this and this is my first post, except for my little introduction. randy
Behold the Vacuum Demons Well, you didn't mention what kind of car - i.e. year, make, model, engine, etc... but generically your best bet is to grab a copy of your shop manual, the one for the year and make of the vehicle which should include every model made, and start tracing the AC/Heater vacuum diagrams to make sure it's all hooked up correctly. Sometimes you can get the same information from a Chilton's or Haynes or the like. If you don't have a chassis / shop manual yet, might as well hit the net and buy one. Plenty of sources for these - OEM is best, repro second. The OEM'ers have color which is a must-have (along with a magnifying glass and some aspirin) for the electrical schematics. The vacuum for AC/ heater systems normally tees off of an intake manifold source, sometimes the line going to the power brake cannister, sometimes just a fitting on the intake. It should not come off the ported tee that also serves your distributor advance, which screws right into a cooland passage and is temperature actuated. Hence, the term "ported vacuum advance." Which, by the way, sucks. As for that port on the back of the carb, my '67 Riviera uses one on her Quadrajet as part of the air injection reactor (AIR) system installed on California vehicles of that particular vintage, but on many other models, including my '69 Riv, this port is plugged/capped (they got rid of the AIR system in '68 and went to something called CCS - never mind). Depends entirely on the vehicle application. The fact that you are pulling only 15" from there, but "full vacuum" (although you didn't quantify this) elsewhere is kind of strange, but then I don't know what kind of car / motor you're running. On my '67 that port reads full intake vacuum, 18", which is ostensibly 18-22" at idle for most cars. Good luck and welcome to V8Buick.
Re: Behold the Vacuum Demons hello thanks for the reply. i guess i'm not the only one up late sorry i have 69 wildcat ,430 engine Q-jet carb 7029240 this problem surfaced after the car sat for 3 years after an accident, and i changed the carb. the old carb was not the correct one for the car, and although it was a Qjet, the ports were in different places. i think it was for a early 80's GMC truck i have the shop manual 1969 buick chassis service manual all series. i also have a fisher body manual, they are both OEM and old and used. i believe the AC/heater vacuum circuitry is correct, because it have a vacuum pump and tested it. this is a manual pump ( like to bleed brakes) and i have to pump it several times after changing the AC/heater mode in order to get the volume of vacuum required to move the AC/heater doors to the new location, but it eventually gets re ?pressureized?. my 69 buick chassis service manual calls the rear port on the carb "main vacuum supply nipple"( page 64-32 figure 64-29). i have been unable to find any documentation showing which port on the intake/carb should be connected to the vacuum canister which is located on the firewall. it is probably in the service manual i just havent been able to find it yet maybe i should connect the vacuum canister to the front passenger side port on the carb. this is called the "Full vacuum nipple". this is the one that is teed to the air cleaner and the ported switch on the intake ??? sorry i wasnt clearer on my problem or my description of my vacuum. thanks for your reply, i am beggining to think that i need to cap this rear nipple, and use the one on the front passenger side. the nipple in the rear eventually comes up to the same amount of vacuum i read on the front/passenger of the carb, but the volume of the vacuum is real low. it takes a long time for it to come up. i emailed the guy i bought the carb from also, maybe he has some information for me . you mention the line from the intake to the power brake. i havent messed with that and i did see one picture in the manual concerning that and i didnt see a "T" on it i left my car with the ported vacuum advance for the time being cause have a big old wildcat and havent tried to squeeze much out of it yet. i only had it for 3 weeks when someone pulled out in front of me ( well i was speeding a little ). it has taken 3 years to get it back on the road, with having another baby(well my wife did) and moving to a new house. but it is back on the road again. my vacuum of the front passenger nipple on the carb is between 15-20 when idling. when i set my timing i did it with a timing light and have now realized i should have set it with vacuum. someday i will correct that and maybe get one of those electronic ignition module kits (pertronix??) thanks for listening and helping, i was just too stubborn to throw this car away after it got hit, and this is where i am at now. most of this is a new experience for me. randy
Just pulled my manual- diagrams in chapter 13 confirm that the line should go to the carburetor, and from the pictures in the carb chapter, it looks like the base of it in back like you thought. Vacuum of 15" should be adequate to run your AC/Heater controls, so maybe the best approach is to test with the pump, starting at the cannister and heading down stream. If the pump guage shows that the vacuum cannister leaks down, replace it, and move downstream until you find any and all leaks. Probably you'll want to replace all the rubber vacuum hoses anyway; thirty-year old rubber has definitely served out its expected lifetime. I did this on my cars, easiest way is just one at a time, and take your time. Painful, especially to your back and neck while under the dash, but not impossible, and an inexpensive repair that will last a long time. System components, such as that AC/Heater diaphragm, and the cannister can be found at a number of antique auto air places on line, or advertised in Hemmings, etc, including:Classic Buicks Good luck.
What I believe you have done is reversed the ports on the cannister. The vacuum, which should by MANIFOLD, in other words, at all times, including idle, should go to the larger port on the cannister. The A/C controls should go to the smaller port. You might also check the cannister for leaks, due to age, and possible concussion damage, due to the accident. It is also possible for the vacuum switch on the A/C controls to leak, adding to the problem. You might also check the diaphragms on the plenum for leaks, which could either slow response, or eliminate it. Ray
hello guys, thanks for the replies. i went ahead and hooked the input to the vacuum canister up to the full vacuum nipple on the front of the card, and the AC/heater controls will work properly on that port. so i believe my problem is that the port on the rear of the carb, the main vacuum supply nippe, is not working properly. it slowly builds up vacuum, but the volume of vacuum is not enough. i emailed the guy who rebuilt the carb and he said to check the gasket to be sure it isnt blocking of the vacuum. well i put a new gasket on when i changed the carb, and it was different from the gasket i removed, but i didnt worry about that because the carb i removed was different from the carb i was puttin on. i can see where the gasket could interfere with the flow of air through this port at the rear of the carb. do i need to modify the gasket on the right to get it to work properly ?? thanks for the help and sorry if this is a dumb question randy ps i reduced the sizes of the pictures, but if they are still too big let me know i submitted a scan of the old and new gaskets. the old gasket is on the left and the new type gasket is on the right. the gasket on the right isnt the exact one that is on my car, but it is the same type. the one on the right came off of my parts car, which had the right carb, but the fuel filter threads were stripped.
i dont know how to submit multiple images at once ?? if you look at the gasket on the right, in between the 2 large barrels, you will see a dark area sorta shaped like a christmas tree. i think this is the area that might need to be modified on the gasket to get air flowing through there and out the nipple in the back of the carb (there is probably a better solution than that, that is why i am asking) sorry for replying to my own posts thanks for the patience randy
it is working now hello guys when i removed the carb and checked the rear nipple, it was clogged up with dirt/soot/sand. i cleaned it out and my AC/heater controls are now working. thanks for all the help and patience randy
Dirt and Sand? In a rebuilt carb? :shock: Did you thank the rebuilder :moonu: for the swell job he did on your Quadra-jammed? SHEESH! By the bye, since you removed, cleaned and then re-installed the carburetor, technically you should use a new gasket. :Smarty: One way is to take the old (new) one down to your favorite parts store and match it up. Or you can order one from Classic Buicks, assuming the carb you got is year / application correct. So what's the plan on the front end? :Brow: E
hello, i had been emailing the guy i bought the carb off of, and he responded quickly and was helpful. he said " It was probably carbon buildup that did not getcooked out???" i got the carb on ebay for $163 with no exchange. it was 'wet tuned' on a bench. i havent turned a screw on it as far as adjustment, maybe i will later but it seems to run fine. the carb was very clean when i got it, he probably just didnt check the back port ? i was a little dissapointed but glad to locate the problem. i have been more upset with the amount of 'shelfwear' on some of the NOS trim parts i have bought. but that is anothe story. i didnt replace the gasket cause it was only 1 month old. i just reused it, with the same sideup as before. it only took about 10 minutes to get it off, so i could replace it. why do i need to replace it if it was still good ??. i am pulling 19' of vacuum at idle, and my timing wasnt set with vacuum, it was initially set with a timing light, but then i fudged it a little after some test drives. not exactly sure where it is right now, but i am running ok. i got my gasket from NAPA , which is where i get most of my parts. i hope that is ok. yes i now have the correct carb for my car. my car was wrecked to the water pump. the frame horn was bent also. i have replaced the front clip and passenger door, and the engine pieces upto and including the water pump. i got it all lined up pretty good except for the hood. i think i have a bad hinge, as it stickes up about 1/2' in the back on the passenger side. i sold the hinges off of my parts car(69 4door wildcat) cause i didnt think i would need them, that was a mistake. i need some hinges or something. i need to take a picture of it so it is back on the road . in primer on the front, and i am working on mechanical stuff this summer, so i can still drive it. shocks,brakes,brake line repairs,carb,gas tank sending unit,tires, and alignment have been replaced so far. i still want to do the passenger exhaust manifold( it is cracked), and replace the exhaust ( should i get an X pipe?). also the 6 way seats quit working over the 3 year downtime. i want to check into that. i also have some vibration i want to nail down. it comes at 45mph(as decellerating through that range) and at 75mph( if get on/off the gas). the vibration at 45mph used to occurr at 35mph until i got an alignment. this fall i intend on getting the whole thing ready to paint. dont know how much of the work i am goint to do myself, as i had never done any body work before. well thanks for the help, and i will keep moving forward randy
