Hi..Guy's Here we have the latest challenge with the 70 Buick GS 455. There are very few Buick guy's around here so once again I will draw on to vast knowledge from this forum. This is a carburetor issue which has turned very frustrating. First some info on the engine. The engine is a completely rebuilt 455, bored 30 over TA C110 cam, MSD Dist & coil and Edelbrock performer intake. The carb. is a 750 Q-jet, was brand new/ remanufactured. Right off we could not get the engine to Idle right. The carb, after adjusting would not stop dripping fuel from the primary nozzles. If you look into the carb with the engine running you can see the fuel pooling on the throttle plates in the bottom. I took the carb off and brought it to a local carb guy with a good rep with Q-Jets. He found the top plate was warped. He located a good one and replaced it. put the carb back on...same thing leaking. I checked fuel pressure its 3 lb's at cold idle. I then borrowed another carb (same style) from a friend. Guess what...same thing leaking. My carb guy took the carb apart again and put a complete rebuild kit in and rechecked the float level. We put the carb back on with the same results. My carb guy said he was stumped and suggested I take the carb into another guy who has been working on carbs for forty years, this guy is a local legend. Anyway he looks at the carb and sez the carb had sticking metering rods...so he fixed that. I put the carb back on and same thing leaking. I know the PCV routing is not done right I am in the process of correcting that issue, ram air is not hooked up at present. I can't see engine ventilation being a big issue maybe miner, but I'm not that sure. I would appreciate any thoughts or help with this latest challenge.
Quadrajet nozzle drip is usually the result of too much throttle opening/angle at idle rpm. Too much air passes thru the venturis and pulls the fuel in dribbles into the airstream and onto the top of the primary plates. I have also seen this caused by too high a float level. A stuck float. A sticking needle and seat. too much inlet fuel pressure . If the idle circuit of the carb is somehow compromised and not supplying enough fuel to hold an idle, you may have had to adjust to a point where you are idling off the main circuit. Throttle angle adjusted so far open that you are idling off the nozzle drip. Did the engine respond to adjustments of the idle mix screws? What kind of vacuum readings are you seeing at what idle rpm? If its only the throttle angle that is causing it, you can remedy this by adding some (more) idle bypass air, which will let air into the engine but bypass the venturis, allowing you to maintain the idle ropm at a smaller throttle angle. BBB qjets generally came with some amount of idle bypass air built in. First things first, what is the number of your Quadrajet?
How many turns are on the idle speed screw? , back idle speed screw all the way out, turn idle mixture screws all the way in then out 1 1/2 turns each, then turn idle speed screw till it starts to move the arm then go another 1/4 turn, if it wants to idle low turn timing up, push come to shove send the carb to "tech8" or "carmantax" here on the Forum, that will rule out any questionable carb conditions, and I see Ken had posted while I was typing, but if the local legend didnt see the throttle was open to far he may wanna leave the carbs alone
Hi Ken These are the # I have found on the carb...17U081200, also 0351 DPN, ....also 17062757 stamped in a circle. Regards, Chris
Look her on the carb for the proper number to go by. My guess is you have idle circuit issues, like Ken mentioned. Many Quadrajets I get in have clogged air/idle tubes. With a cam like yours, they should be enlarged anyway to allow enough air through the idle circuit so you don't get the nozzle drip.
These are the tubes. They need to be pulled, cleaned and sized for each application on the Quadrajet. This may or may not be your entire problem, but is a very common issue. You can see that one of the is clogged when I pulled it. When this happens, it has to idle from the main circuit by opening up the primaries with the idle screw, and then you get raw fuel dumping in. Have a "kit" rebuild won't fix these issues.
Remanufactured Q-jets are the worst option for someone looking to stay with a Q-jet. Remanufacturers start with piles of parts and build "Frankenstein" carburetors with possible incompatible parts, and then they purposely jet it rich so that it will run on most engines. Guys like Cliff Ruggles won't even touch them because the work involved to get them right just isn't worth it. You are better off with a junk yard Q-jet. Then have someone like Ken calibrate it for what you have. The Q-jet gets a bad rap for cases like this. GM calibrated each carburetor for the engine it was to be run on. In addition, there were carburetors for small blocks and big blocks. A big block obviously needs more air at idle than a small block. Try to run a SB carb on a big block, and nozzle drip can be the result. I'd ditch the ReMan and start with a known good core. Just my .02 Cliff has his own Forum for Q-jets, http://www.cliffshighperformance.com/simplemachinesforum/ http://www.cliffshighperformance.com/index.html
17081200 Looks to be a Chevy carb. 81-86 Chevy big block 454 truck unless I am mistaken. At any rate, my experience is that the Chevy carbs have huge air bleeds, huge Jets and lots of idle air bypass. Bottom line the Chevy calibration isnt too Buick friendly. Sure it will work but it needs tinkered with to get it right on your 455. Certainly it will need the idle system modified to provide more fuel, among other things. My recommendation would be to find a Buick 455 carb and go from there. I do have 800cfm Buick 455 Qjets available on my website now. Performance tuned w/ electroplated finish 71 72 73 http://www.v8buick.com/showthread.p...cfm-Performance-Calibrated-Qjets-f-s-71-72-73
Ken... Interestingly enough I knew the carb was for a Chevy because the fuel line comes in from the side not the front. Plus the second carb guy said the carb was for a truck and that he didn't think it was the correct carb for the car. The engine was rebuilt by a guy that does Chevy's and fords primarily, as I have said there are not that many Buick guys around here. Given that I have the wrong carb. Which number carb would you suggest I try to find that would be best for my engine? I have posted a few pics of a carb which is identical to mine. Regards, Chris
If you want to keep the Electric choke function then you want a 1976 Buick 455 Qjet #17056240. It will have a forward facing fuel inlet and can be readily converted to electric choke, mounted on the carb, Do you have anything except the throttle cable attached to the carb's throttle arm?
I hate to jump in your thread but i am having the same problem with my carb. It is a 71 1540 big block carb that i had rebuilt by a friend. This is the 5th q-jet he's done for me and they've all been flawless until this one. It won't pull fuel through the idle circuit and i need to have the primaries open to get a little fuel to drip out the boosters to get it to idle..poorly exactly as you've described in the above post. When set up this way it surges at idle and is generally a pain in traffic but runs well going down the road. I sent it back to my friend and he went through it a second time and i really don't want to send it back a second time. I put a 71 1544 from my stash back on there and it idles like a champ and pulls 16 inches of vacuum so i am almost positive it is the 1540 carb idle circuit that is the problem. I would like to take a stab at trouble shooting this myself and try to gain some q-jet skill beyond writing checks.. So if Ken or Mark would care to offer some guidance i would be grateful..My questions are what is involved with pulling the idle tubes ?? is it as simple as tugging with a pair of pliers? what about reinstalling them..is it a press fit or is there a sealer that i should use. What else beyond the tubes might be clogged causing my lack of idle fuel? Also if i could ask can you explain the idle air bypass? I've heard this term but i could use some detail in where to look to see if this is my problem. Thanks
Chris, I would suggest a 71-74 Buick 455 carb for the 800 cfm flow. These carbs have divorced choke though, so if you want the Electric choke then, like Ken said, go with a 7045240 or 17056240. Both Buick 455 carbs that have the hot air choke that can be converted to electric. I keep these cores in stock to build, and Ken probably has some also. htrd, pulling the idle tubes is a little tricky, but not a huge ordeal. You need to pull the Quadrajet completely apart. The idle tubes are held in to the main body with a collar. You have to tap the tube down, and then pull the collar. I use a sheet metal screw. You need some very small tip drill bits also, the standard Buick 455 carb air tubes are usually .033, and you may need to go to .036 or .038 depending on cam, compression, etc. My 462 idles perfectly, but when one section needs change due to engine mods, you may need changes in the other areas. The basic areas of the Quadrajet to adjust for custom build are: Jets Primary rods Secondary rods/hanger Idle tube Down channel restriction Air bleeds, upper and lower Main bleeds, upper and lower Idle bypass air base plate idle screw holes this is why people think the Quadrajet is complicated to use, but really, once you get these components right, or close to right, the finishing adjustments are not complicated at all, and the result is better performance and fuel economy than an off the shelf replacement.
Thanks Mark, I may have a go at it tomorrow, I have a pretty thorough selection of drill bits so i should be OK there. I also have Doug Roe's book floating around here as well. Once i have the tubes removed is there anything else i should be looking at to make sure there isn't any blockage? I do appreciate you sharing 'trade secrets" with me as i try to figure this out for myself.
Whooooooaaahhhhh, dam your carb expert let you put that carb on your Buick? And then tried to fix it... Yikes man. A really good Roch is gonna be in the 4MV catorgory. You can adjust your primary needle height on those , electric choke, yes, choke and secondary pulloffs, yes, 800 cfm yes, You can find them on old Pontiacs or Buicks, 70ies cars. Pay attention to what float you put in it. The big angular looking ones should be avoided, the 0ne that looks like a square with the inside bottom missing . is the one you want. Good luck, I bet this will be the last time you try to put a cheby part on your Buick.
Actually there are a few more things to look at. I would sugest How to Build horsepower vol 2. By David Vizard, or How to rebuild and modify Rochestoer q jet carbs,
Ken Thankyou for your info. this clears up a lot of the mystery with all the problems I have had with this carb. In answer to your question about the throttle arm...there is nothing else on it.
Thank you guy' for all the useful information. Hopefully with this new information I can get the old GS breathing the way she should.:TU:
Agreed on remanufactured Q-Jets, they're worse than junk. They give a false impression that they will do anything besides pass emissions tests. I rebuilt mine with the proper parts with Cliff's book, and it's had my 430 purring like a kitten for 2 years.
