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I have a 1974 Cutlass Supreme 350 cid with the original Quadra jet(?) carb. When I bought it a couple years ago it started fine but wouldn’t Idle right and would die sometimes at lights. I watched an explanatory video and followed the instructions and thought I had it dialed in pretty good. Started running and idling perfectly with no more stalls. However it has become progressively harder to get started. Starts in a split second with started fluid into the carb and runs perfectly after that. But just about can’t get it started any other way these days. Any suggestions?
2nd question maybe for a different thread. The shop that does all my work, last spring they did a whole bunch of stuff on this car, brake lines, new steering parts, fixed and exhaust leak, etc… said that the carb needs to be replaced. I asked about having it rebuilt and they didn’t seem interested.
This shop does good work but they are really busy (they do most of the classic mechanic stuff for one of the big custom shops in town which is next door) and they’re not cheap so I know they’d rather just replace and get it running right then mess around with a rebuild. But this is a nice classic and Id like to keep it pretty original, but I also need it running right so I wanted to ask the opinions in here are.
I’ve been warned by another cutlass owner in town, absolutely do not by a remanufactured quadrajet either have the original rebuilt or get a nice aftermarket.
Whether I buy a nice new edelbrock or whatever I’ll keep the original so it stays with the car going forward.
What should I do? If a new one any suggestions on brand and model? I’m a woodworker who loves classics, I’m handy but I’m no expert on this subject. Need guidance.
Send it to a carb specialist and have it rebuilt. Due to its age it will probably need to have the throttle shaft bushings redone, this is more than cleaning and new gaskets. Stick with the original Qjet, you'll be much happier.
Agree with keeping the Quadrajet. I have found most people afraid to work on them that's why they recommend an aftermarket replacement carb. One other thought and suggestion is the fuel that you're using. Not sure about and other members but I have found with mine it idles and drives perfectly fine but always is a hard start due to the amount of Ethanol in the fuel. The fuel "boils" out of the carb bowl and therefore is dry to start. If I run Ethanol free it starts, idles and drives beautiful!
I read some articles (lost art of choke adjustment in Hemmings) and threads and watched some videos and from what I can tell the choke plate is not closing all the way. There seem to be at least two things contributing to this that I can see.
1. The choke spring is not tight or at least not tensioning the lever to snap the plate closed and so the plate is limp and doesn’t spring at all. Just hangs open. The only way I can get the spring to tension and close the choke plate is by turning the dial so far to rich the indicator line is far beyond the notches. It will start and idle high but doesn’t sound or smell right and keeps trying to turn over after I shut it off. I guess that’s Running rich?
-I have taken the choke spring cover off probably 20 times but I can’t seem to find a way to tension the spring against the lever without turning the dial beyond rich. The spring seems to be fixed to the dial positions. Is there another adjustment I’m missing?
2. The pull off break(?)(I really hope I’m using the right term here haha) may not be operating properly. There seem to be 3 positions, 1 all the way back where the choke plate can fully close, one slightly forward which opens the plate just a crack, and one all the way forward that opens it all the way. I could be wrong but I think the pull off break is returning to the 2nd position when the car stops which keeps the choke plate open a smidge.
You can see the indicator line in the middle of the markers and the choke hanging open. In order to get it to tension the choke plate I have to run the dial counter clockwise to beyond the 12oclock position. Is the position of that indicator line unimportant? Is all the matters the spring tension in the end or does the position of that indicator line and the dial determine some part of the mixture independent of the spring and choke plate?
I realize I only know enough about this to get myself more confused so stop me if I’m a hot mess.
After getting it running and idling right I feel like I’m so close to having it dependable if I can just fix this starting issue without any major downtime haha.
Last edited by Cinnamon Gravy; Sep 29, 2024 at 09:26 PM.
I read some articles (lost art of choke adjustment in Hemmings) and threads and watched some videos and from what I can tell the choke plate is not closing all the way. There seem to be at least two things contributing to this that I can see.
1. The choke spring is not tight or at least not tensioning the lever to snap the plate closed and so the plate is limp and doesn’t spring at all. Just hangs open. The only way I can get the spring to tension and close the choke plate is by turning the dial so far to rich the indicator line is far beyond the notches. It will start and idle high but doesn’t sound or smell right and keeps trying to turn over after I shut it off. I guess that’s Running rich?
-I have taken the choke spring cover off probably 20 times but I can’t seem to find a way to tension the spring against the lever without turning the dial beyond rich. The spring seems to be fixed to the dial positions. Is there another adjustment I’m missing?
2. The pull off break(?)(I really hope I’m using the right term here haha) may not be operating properly. There seem to be 3 positions, 1 all the way back where the choke plate can fully close, one slightly forward which opens the plate just a crack, and one all the way forward that opens it all the way. I could be wrong but I think the pull off break is returning to the 2nd position when the car stops which keeps the choke plate open a smidge.
You can see the indicator line in the middle of the markers and the choke hanging open. In order to get it to tension the choke plate I have to run the dial counter clockwise to beyond the 12oclock position. Is the position of that indicator line unimportant? Is all the matters the spring tension in the end or does the position of that indicator line and the dial determine some part of the mixture independent of the spring and choke plate?
I realize I only know enough about this to get myself more confused so stop me if I’m a hot mess.
After getting it running and idling right I feel like I’m so close to having it dependable if I can just fix this starting issue without any major downtime haha.
Re-read Post #2 and #3. Make sure they put in a new spring for the choke too.
If it's the original carb, after 50 years it's probably time for a clean and rebuild. Your carb number should be 7043250 if a 350 or 7043251 on a 455. You can find it at the left rear side of the carb body.
How handy are you mechanically? In other words, armed with the 1974 factory shop manual and a bucket of carb cleaner, do you think you could remove, disassemble, clean and reassemble it? If not there ARE trustworthy and competent people who can do it for you and set it up properly. You'd have to ship it to them though.
That's an awfully nice looking Cutlass. Don't let just anyone mess with it. Though I can't understand a shop dealing with older cars that's unwilling to tackle a QuadraJet rebuild. It's a half day job tops depending how grungy the carb is and how long it needs to soak.
Don't let them talk you into a Holley or Edelbrock either. That's a cop-out solution and the engine won't perform as well as what the factory engineers designed for it.
I could probably figure it out, I’m pretty handy when I have guidance but might be easier to just send it in some where. I’ve found a bunch of carb rebuild videos and I’ll probably watch a few just to get the jist and then start calling around to find a shop that does it.
thought I had it dialed in pretty good. Started running and idling perfectly with no more stalls. However it has become progressively harder to get started. Starts in a split second with started fluid into the carb and runs perfectly after that. But just about can’t get it started any other way these days. Any suggestions?
Need more information. Are you pumping the pedal 3-4 or more times before starting? Have you verified there is a stream of fuel when the throttle is actuated? Could be the accelerator pump is not working, which is a simple fix. Or could be a cracked rubber fuel line that causes fuel leak down.
I could probably figure it out, I’m pretty handy when I have guidance but might be easier to just send it in some where. I’ve found a bunch of carb rebuild videos and I’ll probably watch a few just to get the jist and then start calling around to find a shop that does it.
You may be pretty handy. You might be able to rebuild the Quadrajet yourself. If you look for a carb rebuilder, you WANT someone who is very familiar with Qusdrajets, not a shop that claims they do all carbs. Doug Roe and Bill Travato have books to tell you all about your carb.
Since your profile doesn't show what state you live in, we have no idea if a good rebuilder could be near you.
You may be pretty handy. You might be able to rebuild the Quadrajet yourself. If you look for a carb rebuilder, you WANT someone who is very familiar with Qusdrajets, not a shop that claims they do all carbs. Doug Roe and Bill Travato have books to tell you all about your carb.
Since your profile doesn't show what state you live in, we have no idea if a good rebuilder could be near you.
Im in central Texas, Quadrajet power is near me. Also changed my profile to give more info thanks for the heads up
Need more information. Are you pumping the pedal 3-4 or more times before starting? Have you verified there is a stream of fuel when the throttle is actuated? Could be the accelerator pump is not working, which is a simple fix. Or could be a cracked rubber fuel line that causes fuel leak down.
The research I did a few months ago landed me with the impression that I should only be pumping the pedal once to give a squirt of fuel and snap the choke closed, which is what I usually do. On cold starts It won’t start the first tturn of the key, but it usually starts up the second turn of the key.
Lately the more frustrating issue has been the hard starts after it’s been running. Stopping during a cruise and letting it sit for 30 minutes and then it will start but die over and over
Cliff sells the good rebuild kits. You can call him or email him. He'll talk your ear off. Especially if you like guns & bourbon.
Unfortunately hes not willing to rebuild anymore...retired in 2023. I think I got his last three carbs.
Your carb looks nice. If the throttle bushings are tight I'd simply carefully clean and refresh.
The details in how each circuit works must be understood to properly tune any carb.
The AVS door clock spring, the power piston and pump shot are the big ***** to turn. Check the throttle body and air horns for warp.
Smaller details and tricks are revealed by Doug and Cliff, like staking the check ***** before you remove and replace them.
You can send just the throttle body out to get rebushed. At a minimum a good local machine shop can properly "fixture" the part in a mill or drill press and accurately drill out and install new bushings and restake the butterfly screws.
Once back on the car its time to super tuns the carb AND distributor to cope with today's gas.
Are you sure this is the original carb? It looks almost new. It might just need a filter and some fine tuning with a vacuum gauge.
Snap a pic of the float bowl numbers and the 4 digit date stamp on the throttle plate.
Hard starts after the engine has fully heated up could be heat soak. When its hot look down the carb before you do anything. Actuate the throttle engine off and see if you see two strong shots of fuel.
Heat soak can be cured a couple of ways. Float level is one. Blocking off the heat riser crossover the permanent fix.
TB DATE CODE
FLOAT BOWL ID NUMBERS
Last edited by droldsmorland; Jan 2, 2025 at 05:45 PM.
Modern gas is garbage compared to the gas available when your car was new. They will tell you its better, cleaner, etc. But not for our cars, even if yours was designed for regular unleaded. Gas has additives today that bother our engines way of running. You must go with a higher octane rating to try and compensate for today's poor gas quality.
Originally Posted by Cinnamon Gravy
The research I did a few months ago landed me with the impression that I should only be pumping the pedal once to give a squirt of fuel and snap the choke closed, which is what I usually do.
Regardless of how beautiful and or well maintained a car is such as yours, they are 50 years old. You can only go by the book but so much. Adjustments have to be made to get by today. 1 pump starts from an overnight park down can be a tall order for a non computer influenced carburetor. Weather conditions play a big part in this...
Yes my car can start with 1 pump if used daily and its 72* outside. But I need 3 pumps when its 36*. 3 pumps is my magic number, if I crank it and its no go. I pump it another 3 times and crank. Of course this cannot go on too long otherwise you will flood the carb. Sometimes you need to let it crank slightly longer, to engage. You will find a pattern that works best for her.
My formula is similar to 69CSHC. For my 79's I pump 2x then crank for 5 seconds. Then I stop for a few seconds & try again for another 5 seconds or so. This usually starts the car right away, but if that doesn't get it I stop, wait a few seconds and pump 2 or 3 more times and then crank it another 5 to 10 seconds, depending on the outside temp.
Cliff sells the good rebuild kits. You can call him or email him. He'll talk your ear off. Especially if you like guns & bourbon.
Unfortunately hes not willing to rebuild anymore...retired in 2023. I think I got his last three carbs.
Your carb looks nice. If the throttle bushings are tight I'd simply carefully clean and refresh.
The details in how each circuit works must be understood to properly tune any carb.
The AVS door clock spring, the power piston and pump shot are the big ***** to turn. Check the throttle body and air horns for warp.
Smaller details and tricks are revealed by Doug and Cliff, like staking the check ***** before you remove and replace them.
You can send just the throttle body out to get rebushed. At a minimum a good local machine shop can properly "fixture" the part in a mill or drill press and accurately drill out and install new bushings and restake the butterfly screws.
Once back on the car its time to super tuns the carb AND distributor to cope with today's gas.
Are you sure this is the original carb? It looks almost new. It might just need a filter and some fine tuning with a vacuum gauge.
Snap a pic of the float bowl numbers and the 4 digit date stamp on the throttle plate.
Hard starts after the engine has fully heated up could be heat soak. When its hot look down the carb before you do anything. Actuate the throttle engine off and see if you see two strong shots of fuel.
Heat soak can be cured a couple of ways. Float level is one. Blocking off the heat riser crossover the permanent fix.
TB DATE CODE
FLOAT BOWL ID NUMBERS
Ok this is all great Info thanks so much man. I’m gonna prefer me that book and start digging in.
As far as the numbers go it’s all still on the car for now but I’ll snacks of what’s visible. I’m waiting to hear back from Qjet power about a replacement carb before I send it in. I have another thread where I’m trying to sort out the best bolt on replacement while it’s getting rebuilt so we don’t need to go into that here.
That is run on, which is usually caused by bad gas or inefficient octane. If that's not the case something is mimicking the effects of bad gas, etc.
Aha that’s good to know. It’s been a pain in the *** as I’ve had a hard time dealing with it when I’m out cruisin. Usually requires me just taking off and running for a few minutes then it will be fine.
Modern gas is garbage compared to the gas available when your car was new. They will tell you its better, cleaner, etc. But not for our cars, even if yours was designed for regular unleaded. Gas has additives today that bother our engines way of running. You must go with a higher octane rating to try and compensate for today's poor gas quality.
Regardless of how beautiful and or well maintained a car is such as yours, they are 50 years old. You can only go by the book but so much. Adjustments have to be made to get by today. 1 pump starts from an overnight park down can be a tall order for a non computer influenced carburetor. Weather conditions play a big part in this...
Yes my car can start with 1 pump if used daily and its 72* outside. But I need 3 pumps when its 36*. 3 pumps is my magic number, if I crank it and its no go. I pump it another 3 times and crank. Of course this cannot go on too long otherwise you will flood the carb. Sometimes you need to let it crank slightly longer, to engage. You will find a pattern that works best for her.
Aha that’s great to know, I have suspected that there are basic guidelines but there’s a magic equation I’ve got to find so I’ve been trying to pay attention to details when I start.
I’ve flooded the bowl before so I know the limit in that direction, now I've got it starting off one pump on the second turn of the key. I’ll try giving it 2 pumps before the first turn and see what I get.
Thanks for the insight.
I have looked into the Holley EFI stuff but for now I like the idea of keeping it original and the opportunity to dig in and learn more about the system.
My formula is similar to 69CSHC. For my 79's I pump 2x then crank for 5 seconds. Then I stop for a few seconds & try again for another 5 seconds or so. This usually starts the car right away, but if that doesn't get it I stop, wait a few seconds and pump 2 or 3 more times and then crank it another 5 to 10 seconds, depending on the outside temp.
Yeah this is basically what I’ve settled on, but one pump then crank for a few and take a few seconds break, then crank again and it usually goes.
I do love hearing it start 😁 I’ve got a mild Flowmaster 50 series on it but it still sounds great 👍
loved seeing your car pics. i had the same car my junior year of high school, other than my wheels were color matched and wide raised letter tires. thanks for the flashback
loved seeing your car pics. i had the same car my junior year of high school, other than my wheels were color matched and wide raised letter tires. thanks for the flashback
Man so many people have stopped me to tell me about their relationship to this gen Cutlass. I love it and happen to share!!
Were you able to sort the choke blade not closing mentioned in post #6?
Yeah I just dialed the spring a bit tighter. I have a new spring and choke cover I haven’t put on yet. I’m also waiting on a new hot air choke tube as well mine is about rusted out.
The rotted tube is why the choke is giving you a hard time.
Electric choke kits are available. They work much better.
Not sure if its been mentioned yet, but do not toss or turn in OEM parts for core charges. The OEM stuff is USA, everything else is not.
You are far better off rebuilding parts, carbs, alternators, masters, PWR steering pumps et al.... Even that old choke cover and spring may be better than the replacement you just bought. Unless its NOS.
The rotted tube is why the choke is giving you a hard time.
Electric choke kits are available. They work much better.
Not sure if its been mentioned yet, but do not toss or turn in OEM parts for core charges. The OEM stuff is USA, everything else is not.
You are far better off rebuilding parts, carbs, alternators, masters, PWR steering pumps et al.... Even that old choke cover and spring may be better than the replacement you just bought. Unless its NOS.
Oh yeah for sure I’m not tossing anything. That’s why I haven’t replaced to original dial and spring yet. The plastic cover on the knee just feels cheap. I was going to wait for the new tube and then see how it worked.
If I recall correctly the bi-metallic choke thermostat could be installed backwards. It would be worth removing the cover, taking the spring off, turning it over to see if it tensions the choke blade at its correct position.
If I recall correctly the bi-metallic choke thermostat could be installed backwards. It would be worth removing the cover, taking the spring off, turning it over to see if it tensions the choke blade at its correct position.
yeah, I thought about that. I also thought about taking the new spring off the new cheap dial. I got and putting it on the old original dial.
Is the spring just held in place by clamping those two metal pieces together? Or is it soldered in there or something?
