1983 Monte Carlo CL. 35k original miles. 305 turbo 350 trans. Does anyone know what I will need and how to go about eliminating the computer, emissions, quadrajunk carb to Holley 600?
Quadrajunk to Holley Conversion help!
- Thread starter GBodyShuffle
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You will want to get a 1975-80 non-computer HEI sbc distributor(easy found in junkyard or craigslist), get a spreadbore to squarebore carb adapter, and then you can basically just take the computer out and the other related smog equipment; it will no longer be needed. You also can get a 78-80 gbody non-computer pass side kick panel if you want to clean it up a little. Do you already have the carb? You can also buy a holley quardrajet replacement carb that will bolt up to your stock intake without the carb adopter if you're worried about hood clearance; that's what I did. Getting the non computer HEI is very important as your car will never run right if you leave your present one in there with a non computer controlled carb. I would go with a good used GM unit rather than an aftermarket elcheapo HEI, unless you're willing to spend the money on a Mallory or MSD unit.GBodyShuffle said:
Don't forget you will also need a throttle cable/tv cable bracket. Many companies make them that can be used on any trans cable type. Make sure if you have not already bought a carb you do some research, most people buy a Holley that is way to large for the application. The Holley website has a decent carb selector tool but the best thing is to call them
The fuel pipe and throttle linkage will need to be modified. Plus, you may need to spend some time dialing in the Holley to your engine with jet changes, etc. If you have not already bought the Holley, you may want to consider just putting a non-computer Qjet on there. By the time you scrounge up all the parts, buy adapters and swear a lot, your 305 might be just as happy with a freshened-up non-comp Q-jet. You can migrate your electric choke to replace the manifold-heated version on the older Qjets. Just need a Torx-15 screwdriver (same as some of the headlight trim screws...)
With that amount of miles, what is wrong with the Qjet? If you're looking to make power, the Qjet shouldn't be the issue, not unless there is something seriously wrong. Unless you are racing, you'll find that a Holley is a PITA for daily driving because they are affected by changes in temp and humidity...especially if you live in places where it gets colder than 50ºF during the colder months.
Chevy's now long-discontinued Emissions Legal ZZ4 350 Engine Conversion for '82-87 Camaro's and Firebirds (google it), used the car's original E4ME Q-Jet, a new set of slightly richer metering rods w/ hanger, & a modified-program PROM (chip).... plus a list of parts.. but the core system was the same CCC system, minus the EGR, because the ZZ4 does not have a provision for it... turn key, 50-State Legal conversion, with a GM Warranty on top of that.... again 100% Emissions Legal... ie passed smog.
Quadrajet carbs are not junk, but like anything, if its not maintained, it won't work properly. The E4ME was THE best all-around carburetor ever designed... electronic choke, computer-controlled idle circuit that holds the magic 14.7:1 air to fuel ratio, can flow 750 cfm (no street engine would need ever that much nor most drag engines for that matter.) ... it was so good at what it did, that Chrysler, Ford, & AMC all used it on their early-mid 80's V8's because their carbs were not up to the task of meeting Federal limits... it was the last evolution before true EFI systems were available... The computer is ONLY controlling the idle circuit of the carb, as you step on the gas, the carb functions normally as any carb would, especially when you mash the gas... if your car bogs, its because the carb is flooding the engine because you are dumping more fuel than the engine can handle... ie, learn to feather into the gas & think about improving the engines abilities with a better streetable cam profile and head work.... OR something is wrong and the computer is pulling timing.
Not saying you did, but if you ripped off all of the vacuum lines and plugged them up, expect the engine run crappy.. the carb is part of a system, the GM Computer Command Control or "CCC". The distributor is also part of this system... unlike older GM HEI's, these Distributors Advance/Retard function is entirely dependent upon information received from all of the system's components... if you unplug things, expect poor performance because the computer puts the engine into Limp Home mode... causing it to run rich and limits rpm by pulling timing to prevent enhine damage. On all L69's (HO 305 VIN"G"), some '85 LG4's , & all '86-up LG4 305's (LG4 = 305 VIN"H"), Chevy added a Knock Sensor to prevent "Knock" aka detonation caused by poor fuel grades or a lean condition... if knock is detected, the computer would pull timing until the knock stopped, causing the engine to lose ability to rev. higher..
Chevy's now long-discontinued Emissions Legal ZZ4 350 Engine Conversion for '82-87 Camaro's and Firebirds (google it), used the car's original E4ME Q-Jet, a new set of slightly richer metering rods w/ hanger, & a modified-program PROM (chip).... plus a list of parts.. but the core system was the same CCC system, minus the EGR, because the ZZ4 does not have a provision for it... turn key, 50-State Legal conversion, with a GM Warranty on top of that.... again 100% Emissions Legal... ie passed smog.
Quadrajet carbs are not junk, but like anything, if its not maintained, it won't work properly. The E4ME was THE best all-around carburetor ever designed... electronic choke, computer-controlled idle circuit that holds the magic 14.7:1 air to fuel ratio, can flow 750 cfm (no street engine would need ever that much nor most drag engines for that matter.) ... it was so good at what it did, that Chrysler, Ford, & AMC all used it on their early-mid 80's V8's because their carbs were not up to the task of meeting Federal limits... it was the last evolution before true EFI systems were available... The computer is ONLY controlling the idle circuit of the carb, as you step on the gas, the carb functions normally as any carb would, especially when you mash the gas... if your car bogs, its because the carb is flooding the engine because you are dumping more fuel than the engine can handle... ie, learn to feather into the gas & think about improving the engines abilities with a better streetable cam profile and head work.... OR something is wrong and the computer is pulling timing.
Not saying you did, but if you ripped off all of the vacuum lines and plugged them up, expect the engine run crappy.. the carb is part of a system, the GM Computer Command Control or "CCC". The distributor is also part of this system... unlike older GM HEI's, these Distributors Advance/Retard function is entirely dependent upon information received from all of the system's components... if you unplug things, expect poor performance because the computer puts the engine into Limp Home mode... causing it to run rich and limits rpm by pulling timing to prevent enhine damage. On all L69's (HO 305 VIN"G"), some '85 LG4's , & all '86-up LG4 305's (LG4 = 305 VIN"H"), Chevy added a Knock Sensor to prevent "Knock" aka detonation caused by poor fuel grades or a lean condition... if knock is detected, the computer would pull timing until the knock stopped, causing the engine to lose ability to rev. higher..
You may also need a method to lock up your torque converter ( if your T350 is a lock up trans).
I know you've probably already made up your mind to do the swap, but maybe just a well rebuilt Q-jet will do what you want, and cause fewer headaches. It will take significant time and tuning to get the Holley close to what you need. Most that have eliminated the Q-jet report poorer mileage vs a good running Q-jet. Remember, the ECM Controlled Q-jet was as close to Fuel Injection with a carb as GM could get. It attempts to maintain a perfect 14.7/1 Air Fuel ratio. The smaller front barrels give good mileage when cruising around, while the huge secondaries give you all the fuel you need when you stomp on it. BTW, the ECM does not control the Q-jet on WOT.
Many have reported good results using MountainMan to rebuild their carbs ( or to buy rebuilt). He could also supply a non-ECM qjet, if you wanted to eliminate the other controls.
I know you've probably already made up your mind to do the swap, but maybe just a well rebuilt Q-jet will do what you want, and cause fewer headaches. It will take significant time and tuning to get the Holley close to what you need. Most that have eliminated the Q-jet report poorer mileage vs a good running Q-jet. Remember, the ECM Controlled Q-jet was as close to Fuel Injection with a carb as GM could get. It attempts to maintain a perfect 14.7/1 Air Fuel ratio. The smaller front barrels give good mileage when cruising around, while the huge secondaries give you all the fuel you need when you stomp on it. BTW, the ECM does not control the Q-jet on WOT.
Many have reported good results using MountainMan to rebuild their carbs ( or to buy rebuilt). He could also supply a non-ECM qjet, if you wanted to eliminate the other controls.
First off let me say THANK YOU to everyone for giving straight forward and positive responses unlike some of the other forums I've been to.
Okay, so the reason I wanted to do this conversion is because my qjet is starting to give me trouble. Mixture control solenoid, tps codes and it's been running really rough at idle. No vacuum leaks, new plugs cap and rotor. Still idles rough, doesn't want to stay running when I come to a stop, but it's so intermittent whenever I get the knerve to fix it it stops but then starts up again! I just don't know anymore. Keep the qjet and get it rebuilt? Or just but a new reman. Vehicle is my daily driver so that's why this is so difficult to deal with. Plus there's literally nobody in my county that knows what to do with carbs
Okay, so the reason I wanted to do this conversion is because my qjet is starting to give me trouble. Mixture control solenoid, tps codes and it's been running really rough at idle. No vacuum leaks, new plugs cap and rotor. Still idles rough, doesn't want to stay running when I come to a stop, but it's so intermittent whenever I get the knerve to fix it it stops but then starts up again! I just don't know anymore. Keep the qjet and get it rebuilt? Or just but a new reman. Vehicle is my daily driver so that's why this is so difficult to deal with. Plus there's literally nobody in my county that knows what to do with carbs
If you live near sea-level, you can buy a rebuilt one and generally they will run fine right out of the box once you dial in the timing. Try to hook up all the emissions hoses if you can. Check the rubber is not cracked. Vacuum leaks can be pesky faults that come and go and also lean out the motor at idle and help make it die at traffic lights.
I knew you'd get flamed on the "quadrajunk" swap. I'm one of few on here that don't like them myself, I'd take an edelbrock any day of the week. Holley would be my second choice.
I hope you can get your Qjet straightened out. I think you'll be happier in the long run if you keep it.
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