Quadrajet 4MV tune process
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Joined: Sep 2013
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From: Australia
Quadrajet 4MV tune process
Firstly I must wish you all a Healthy and Happy New Year for 2021 from downunder.
I am in Australia population 25 million and 50 years on minimal real experts to speak of on QJ's. I have read so many posts on CF but not been able to find my answer and was wondering if anyone would mind advising me on how I can tune my factory original numbers matching 1972 Corvette Coupe 454BB (7042217). I am mechanically minded but not of the caliber of some and so the mine field of solenoids, vacuum ports and adjustments has overcome me on this smog engine. I will be using a vacuum gauge as a point of reference and really just need a process of connect this, disconnect that and adjust this. Any thoughts as to how you get to that 'Sweet Spot' on yours would be greatly appreciated.
Thanking you in advance ... ALLAN
I am in Australia population 25 million and 50 years on minimal real experts to speak of on QJ's. I have read so many posts on CF but not been able to find my answer and was wondering if anyone would mind advising me on how I can tune my factory original numbers matching 1972 Corvette Coupe 454BB (7042217). I am mechanically minded but not of the caliber of some and so the mine field of solenoids, vacuum ports and adjustments has overcome me on this smog engine. I will be using a vacuum gauge as a point of reference and really just need a process of connect this, disconnect that and adjust this. Any thoughts as to how you get to that 'Sweet Spot' on yours would be greatly appreciated.
Thanking you in advance ... ALLAN
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From: Lachute QC
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I have advised Allan to simply set the carb up to its stock specs, and it will run very well. There is no sequence of connecting or disconnecting anything - set it up to the stock specs and it will perform. No need for a vacuum gauge. The 1972 Chevrolet Service Manual has step-by-step instructions with photos, and has all the required stock specs. The manual is not in error - the process and specs are correct. Allan is seeking other advice.
Lars
Lars
Last edited by lars; Dec 31, 2020 at 11:11 AM.
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From: Crossville TN
Ahhh..... Everyone wants to make this process harder than it really is. Get the ignition system working properly, set the timing for 'performance, make sure the carb butterflies open completely at full throttle with the accelerator PEDAL, and adjust the carb features properly per the Chevrolet Chassis Service Manual.
Knowing that the carb is built properly is important. But, if you have the original carb on the engine and it hasn't been "butchered" by some rebuild shop, it should be fine with a simple rebuild and proper adjustments.
Knowing that the carb is built properly is important. But, if you have the original carb on the engine and it hasn't been "butchered" by some rebuild shop, it should be fine with a simple rebuild and proper adjustments.
Thread Starter
Instructor
Joined: Sep 2013
Posts: 215
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From: Australia
Thank You my1970conv!
I have advised Allan to simply set the carb up to its stock specs, and it will run very well. There is no sequence of connecting or disconnecting anything - set it up to the stock specs and it will perform. No need for a vacuum gauge. The 1972 Chevrolet Service Manual has step-by-step instructions with photos, and has all the required stock specs. The manual is not in error - the process and specs are correct. Allan is seeking other advice.
Lars
Lars
Ahhh..... Everyone wants to make this process harder than it really is. Get the ignition system working properly, set the timing for 'performance, make sure the carb butterflies open completely at full throttle with the accelerator PEDAL, and adjust the carb features properly per the Chevrolet Chassis Service Manual.
Knowing that the carb is built properly is important. But, if you have the original carb on the engine and it hasn't been "butchered" by some rebuild shop, it should be fine with a simple rebuild and proper adjustments.
Knowing that the carb is built properly is important. But, if you have the original carb on the engine and it hasn't been "butchered" by some rebuild shop, it should be fine with a simple rebuild and proper adjustments.
It's a pain keeping my car original as most I see in OZ have had the 'Bubba Magic', it is too easy to just put fuel injection on. I want to fly your flag on our '72 smog 270 horse but I don't think I have 'Performance' as opposed to 'Sweet'. In keeping with originality the factory carb was sent away by the previous owner for a refresh and has served me well for 7 years. I'm hearing you, Thanks!
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Joined: Jan 2006
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From: Crossville TN
Having your stock engine tuned for "performance" does not mean it is for racing purposes. It only means that you are optimizing the engine 'adjustments' to provide you with the capabilities designed by Chevy Engineering in the first place. It is better for the engine and for you (and your wallet), too. Whether you choose to put your foot to the floor [or not] is up to you. Why anyone would choose to set up the engine as is was sent from the factory [de-tuned for GM's reduced warranty expenses] is beyond me.
But, don't listen to what folks with many years of actual experience with these machines (and vehicles in general)....just salute GM's flag and do what you must.
But, don't listen to what folks with many years of actual experience with these machines (and vehicles in general)....just salute GM's flag and do what you must.
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Instructor
Joined: Sep 2013
Posts: 215
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From: Australia
Thank You 7T1,
Having your stock engine tuned for "performance" does not mean it is for racing purposes. It only means that you are optimizing the engine 'adjustments' to provide you with the capabilities designed by Chevy Engineering in the first place. It is better for the engine and for you (and your wallet), too. Whether you choose to put your foot to the floor [or not] is up to you.
Beautiful 100% totally agree! ... that is what I want so where do we go from here, is it the 1972 Chevrolet Service Manual as recommended by LARS.
Why anyone would choose to set up the engine as is was sent from the factory [de-tuned for GM's reduced warranty expenses] is beyond me.
Me too now things are getting explained ... Because I know no different and have no idea about GM's warranty policy or procedure from 50years ago ... I have a '72 Vette, '72 AIM and a '72 Parts Book and I am aware of NCRS so I press forward to have her as close to original as possible resorting to the CF for the facts and help offered about my car.
But, don't listen to what folks with many years of actual experience with these machines (and vehicles in general)....just salute GM's flag and do what you must.
I listen, I actually hang on everything I'm told about my car and its history. I can also sense when professionals are busy by giving short answers and so not to bother them I ask others. (BTW reference to flag was actually US not GM for our All American Shows)
Beautiful 100% totally agree! ... that is what I want so where do we go from here, is it the 1972 Chevrolet Service Manual as recommended by LARS.
Why anyone would choose to set up the engine as is was sent from the factory [de-tuned for GM's reduced warranty expenses] is beyond me.
Me too now things are getting explained ... Because I know no different and have no idea about GM's warranty policy or procedure from 50years ago ... I have a '72 Vette, '72 AIM and a '72 Parts Book and I am aware of NCRS so I press forward to have her as close to original as possible resorting to the CF for the facts and help offered about my car.
But, don't listen to what folks with many years of actual experience with these machines (and vehicles in general)....just salute GM's flag and do what you must.
I listen, I actually hang on everything I'm told about my car and its history. I can also sense when professionals are busy by giving short answers and so not to bother them I ask others. (BTW reference to flag was actually US not GM for our All American Shows)
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From: Crossville TN
I do wish you luck in your quest. I just think you are making this a lot harder than it needs to be. All of us have been where you are now. Why not think about some 'experienced' advice provided to you. We understand your goals of maintaining originality. But in doing so, you don't have to short-change yourself. The engine/controls have 'variables' which are designed and meant to be used by the owner. We are just suggesting that you employ those adjustments wisely, rather than going by the GM mantra of the day.