Okay well my 84 z28 has basically a junk carb on it. Only runs at full throttle or idle. Unless the choke is kept almost completely closed then it runs all rpm ranges but obviously lacks power. So seems like it's starving for fuel. Anyways I'm looking to upgrade to an edelbrock or possibly holley carb. What I need to know is what all do I need to get to do this? Besides the carb.

And how many cfm should i look for in the new carb, keeping fuel economy in mind for now? Could I use a spread bore to square bore adapter or do i need a whole new intake? Also anything I need to do to my stock fuel system? Anything I need to change about the choke since I'll be getting an electric choke carb? Any ignition system changes like distributor or anything? And can I just put on the new carb and possibly intake and drive off or is there anything I need to worry about since my current carb is a computerized quadrajet?

Basically I'm a total newbie to carbs and need to know anything and everything possible about how to swap my computerized quadrajet to an edelbrock square bore non computerized carb.

Thanks all.

 

You will need some additional things to make the conversion. I went through this process last summer, it was relatively painless. I'll through it out there - you may want to just have the CC-Qjet rebuilt and keep that carb. It has more than enough power capacity for any medium build SBC, and will offer better fuel mileage than any other setup. If you have things that prohibit you from easily going that route, then going to a non-computer controlled setup might be the ticket. You will need to decide on a carb - Edlebrock demand based carbs do work very well, and are quite easy to setup. The electric choke simply hooks up to a key-on 12v power source. The existing fuel line needs to be re-routed, there is a kit you can buy to pick it up at the stock location, or you can simple cut some hose and do it yourself.

Now, I'm sure before the end of the day somebody is going to jump in and tell you the Edlebrock is a set down from the CC-Qjet - they are correct, the Edlebrock offers nothing then Qjet doesn't other than decrease fuel mileage - performance differences are degligible, either carb will work very nicely when tuned right. The Edlebrock does have the advantage of being quite a bit simpler and easier to work on, tune, etc. Holleys are another ball game - a double pumper style carb offers certain performance capabilities above and beyond the demand based carbs, mainly in throttle response and overall peak power. They also a slightly more complex design and require a little more investment of time to spend learning and tuning them. A mechanical secondary carb such as a Holley should be avoided on an automatic with a stock stall converter and numerically low ratio rear-end gearset - unless the owner is willing to really pay attention to when they are going to drop the hammer.

When you replace the carb, you'll need a new distributor, the one in place currently has its advance controlled by the computer, which will not function properly without the CC-Qjet. Its relatively painless to swap over to a vacuum advance distributor and set that up.

You post doesn't mention a few key things - mainly the transmission you have, and the displacement of the engine. Those two things matter quite a bit. If you have an automatic transmission, you'll want to consider that you will loose the lockup ability of the torque converter, and this will impact fuel mileage negatively. There are kits to rig a manual or vacuum controlled switch, if you drive the car regularly you may want to consider this. The size of the engine, and the modifications, if any, are pretty important to the carb size selection. A 600cfm model would support a medium built 305, or a fairly stock 350. A 350 with any breathing mods will probably fair better with a 750cfm carb. A sqaurebore can bolt up with an adaptor to a spreadbore manifold. Depending on the manifold, you may not need an adaptor, my ZZ3 manifold took my 1406 Squarebore Edlebrock with just a gasket no problem.

 

Doh knew i forgot something. It's an automatic 305. Looks to be completely stock. If i do decide to go that route with it then I'll have to consider that toque converter lockup switch. Thanks for all that very helpful information atleast it gives me a basic understanding of what I should be looking for and considering with the swap. Part of the reason for the swap is actuall appearance, new intake and carb, and air cleaner would looks better than factory. And on top of that it should fix my running problem.

 

Ok I have pretty much decided to swap in an edelbrock carb instead of the q-jet. So what would a complete parts list of what i'll need be.

Heres what I know of right now let me know if anything else is needed or if something i've listed isn't needed.

HEI distributor, rotor, cap, and coil. Edelbrock 600cfm carb, squareflange carb to spreadbore intake adapter plate. And thats all I know of so any changes or additions to that?

And how do I hook up an HEI distributor and what not in my car? Do all the original vacuum lines that were hooked to the q-jet still all need hooked up or are there some I should or could get rid of? Oh and what should I do with the old electrical wires that were for the q-jet that i won't need anymore? And is there a way to keep my check engine light from coming on after I put this all on?

Looking to buy all the parts tomorrow and have the car all back together and up and running that day or the day after. Is doing all the whole swap even possible within 1 day for a carburetor amature?

Thanks alot guys.

 

Bump any install help guys?

 

Why would you pay money to downgrade to a smaller (600cfm vs a 750cfm = less power potential) less sophisticated (non-cc vs cc = less mileage), carburetor?!?
I'd just get a new cc-qjet and leave the distributor alone.
Lockup switch for the torque convertor is just another hassle that a non-cc carb brings to the table.

 

If you knew how well the stock carb performs when it's running properly you wouldn't be considering a swap. Hope you change your mind.

 

You'll need more length on the fuel line, or to purchase an adaptor to hookup the Edlebrock carb's fuel inlet, near the top passengers rear of the carb, the the stock q-jet hookup location.

Installing the HEI is a snap, just remove the old distributor, install a vacuum advance HEI distributor, hook up the original power, ground, and tach signal wires - the original clip will attach to the vacuum advance distributor, and then supply the vacuum canister with vacuum from the un-ported side of the carburator. Set the time with the vacuum advance disconnected (and plugged) to about 8-12* btdc, and you're ready to rock. An HEI distributor does not require a seperate coil, it is in the cap.

You'll have to make some decisions on what you want to do with the vacuum lines. If you intend to keep all the stock equipment, such as the air system, the charchol canister, EGR, etc, you'll need to do some tee-ing to supply all those accesories with vacuum, the Edlebrock doesn't have nearly as many vacuum ports as the q-jet. You may choose to elimate some of the emissions systems, you can find guides on the message boards to eliminate all of the above mentioned systems, which does simplify the engine bay quite a bit.

You can remove the entire wiring harness for the computer if you elimiate the CC-qjet and cc-HEI. There are several connections you'll need to unhook, but it is esentially worthless if you're not going to use a CC-qjet. You can even remove the PCM under the dashboard.

Sonix makes a good point - there is no power or fuel economy advantage to doing this swap. A 600 CFM carb on a mild 305 is not a downgrade, a 750cfm carb is oversized - but in either case you're not going to have more power potential with this setup. It is argueable easier to work on and tune, that is why I went with the swap. My car is just a weekend toy, I like to be able to do some tuning with a set of jets and a timing light, and not much else. Do understand you will take a hit in the fuel mileage, and probably not make any signifigant gains. If you're computer controlled setup is not working right, its very possible to find signifigant gains. When I swapped over I was able to get the tune dialed in and obtain much better performance and response. (Bracing for the flame for not repairing the cc setup)

 

Yeah one of my fears with the stock cc q-jet is that the computer system will be messed up in some way and thus not fix my problem or just make a new one. The hit in gas mileage has been running through my head alot, although at the moment I'm getting horrible mileage and have zero power. Like with cruise on on the highway set to 65mph it kicks down just so it can catch back up to speed, everytime I go up a slight hill or take a decently sized corner. My other thoughts against the edelbrock are it's not totally pull off old carb and put on new one. But at the same time that doesn't really matter if I do it this weekend in my cousins garage. It's going to cost me more money to switch from q-jet because I can get a rebuilt cc q-jet off the net for like $220 before shipping. But I'm considering swapping in a 350 or 383 over the winter when I've got a little honda or something as a winter beater/daily driver again. And all the new carb, intake and ignition parts would swap right over to the 350 or 383 from the 305. But I'm sort of starting to think that on the fact that it's my current daily driver it might be better to just go with the larger cc q-jet to keep as much gas mileage as I can, and save some money. Maybe buy me some chrome valve covers or a chrome air cleaner or something.

Oh but I am thinking that I'm going to remove most of the emissions stuff under the hood though, like the AIR pump and all the lines for it and possibly some other stuff if I can figure out what I don't need to clear up the clutter and elimate more possible vacuum leaks. What can I remove still with the factory cc q-jet on there?

 

I'd ditch the air, and thats about it, the rest of the equipment does serve a pretty useful purpose, and if you're going to stay with the stock stuff, thats the way to go. If you're looking for daily driver ability and the best possible gas mileage, the CC-QJet is the carb for you. You can always ship yours out for a rebuild and tune, or there are plenty of them floating around the used market for not too much, I sold mine for $40 when I was done with it.

 

There's a thread started by Nate86 somewhere that has a lot of good info on re-building your q-jet. There may also be a few known good ccc-qjets available from members here.

 

That is an unreasonable fear.

The ccq-jet will handle the swap better than any Edelbrock.

Why? The stock LG4 air cleaner is wanting, but chrome valve covers don't help anything.

You need to retain all sensors. Without the EGR solenoid, the ECM will set error codes (SES light). Technically, by Federal law, you can't remove any of it.

 

Okay well i didn't know how possible it was for the CC system to get messed up.

I didn't know if a stock 305 carb would handle the extra demand of a 383.

And it makes it look better. Those aren't to improve performance or anything obviously. My engine compartment is just very very dull.

Yeah I knew it would without the EGR, I just meant like the smaller items, some of which having multiple vacuum lines going to it which seems redundant. And the Federal law thing doesn't really matter much, my area doesn't do emissions testing. And a previous owner already took the cat off and un hooked the air pump just left everything in place.

 

Oh and I did order a rebuilt cc q-jet from this place https://guaranteedcarbs.com/cgi-bin/...8&keywords=all

 

Some won't. There's a tech article linked from the thirdgen.org homepage (and in the "welcome to the carb forum" sticky) that explains how the secondary air valve may be travel limited, and what to do about it if it is. Most likely the rebuilt carb you have on the way won't have that issue, but it's worth checking.

 

yeah thanks. I'll look that up. Hopefully it doesn't but in the event it does when and if I swap motors it'd be nice to know in advance what to do. Right now I'm still just hoping that the new carb fixing the issue. I think it should since mine runs okay with just very low power if i hold the choke most of the way closed so it gets less air for the amount of fuel it has.

 

It may not be as simple as plug and play but if adjustments are needed they'll be simpler and easier than the same type adjustments on a mechanical carb, promise. Let us know when you get it on there and we can tell you what to do.

 

Okay I got the new carb on yesterday. She runs great. I might need to adjust the choke a little bit because when i start it cold it stalls back out unless I give it gas for a few seconds. Then it's usually alright.

And btw. I'm definately not regretting getting the CC quadrajet over the Edelbrock. The quadrajet gets alot better performance than I would have figured.

 

Glad to hear it!

You can usually figure on doing small, fine adjustments to even a rebuilt carb. High idle speed is one of those adjustments.

 

My idle is actually only right around 600rpm or so which i don't know what it's supposed to be exactly but that seemed pretty decent. The choke is a simple adjustment i know. I just need to do it one of these mornings that I don't have to go somewhere right when i wake up.

 

How is it running off-idle when warm? Hesitation coming into light throttle from a stop can indicate a need to adjust the Idle Air Bleed for proper dwell. A fairly simple procedure but it does require a dwell meter.

Torque Converter locking correctly? Getting good mileage-20+? Yes answers indicate that it is going into 'closed' loop properly.

 

Or a scan tool like Auto X-ray.

I assume you meant going into closed loop properly.

 

Not sure about gas mileage yet. Only put around 80 miles on it since i filled the tank after the carb went on. But the results this time won't be totally acurate anyways. Because to be honest, I've been laying into it a bit because I've finally got some power there. Off idle seems okay unless I stuff it off the line, it like picks up, hesitates, then goes again. But just giving it light throttle off the line it seems like it's fine. I'll pay more attention to it now just to be sure.

I would imagine the Torque converter lockup is working correctly I'm pulling around 2200 rpm at about 65mph on the expressway. Does that sound like it's working? This is my first car with an auto so I'm some what clueless.

 

'Feedback mode'

To check for TC lockup: Tap the brake while cruising at constant speed/throttle position. The brake switch should disengage the lock up and the rpms should flare up a bit. After you drive it for a bit you'll get used to noticing when it engages.

 

Okay did that. And the RPMs don't change what so ever. But 2100rpm at 65mph doesn't seem bad. Idk what the numbers should be if thats off. So could someone tell me roughly how many rpms I should be running for a given speed at cruise?

 

RPMs at cruise aren't too important. They can be close to the same during light cruise with or without lock. Lock does promote better cooling in the trans and is necessary to prolong its life.

Lack of lockup indicates that the ecm MAY not be operating in feedback mode, although there could be other causes. Your rebuilt carb may be out of adjustment enough so that the ecm is not getting good readings from the O2 sensor in order to re-write the mixture vs. VAC sensor/TPS blocks. If this is the case it's likely operating on its last known good settings.

Either way I'd advise acquiring a meter (or x-ray) and determining whether the system is operating correctly and adjusting it if required. If/when you get ahold of one, we can walk you through the simple checks.

If the system is good, time to chase down that lockup problem.

 

I don't know if it means anything but the check engine light never comes on since the new carb went on. And i do seem to have a little bit of a miss at idle. I'm going to get the timing checked soon to maybe fixed the miss at idle.

I know absolutely nothing about adjusting a carb. So if i can get one of those meters you guys will probably have to walk me through everything. Which goes to my next question, where can i get one of those?

Oh and if this auto fails earlier than it should it won't be a total catastrophy(sp) I want to do a 5-speed or 6-speed swap eventually and this tranny dying could give me a good reason to do it. lol. But I would like to not have to do that until i get another car as a daily first.

 

You're not getting someone else to check the timing are you? You really need to learn to do that yourself. It's pretty basic. A timing gun can be had for less than the cost of paying someone else.

A dwell meter can be picked up at any parts store. Should be less than $30. Used to be you could borrow one from someone as everybody had one. Not necessarily the case anymore.

We can walk you through timing and dwell adjustment, no problem.

 

Cheapest timing guns I've found are my area are about $90 and for something I'd use once in a great while it didn't seem worth it. But if I can find one to borrow I might still do it myself. I know how to check timing I just don't have my own gun. The dwell meter I got no clue I'll have to start looking for those and I've not no idea how to use that. So you will need to walk me through that one.

 

You can get a light thru Summit for 40-50 but will pay the extra 10 in 'handling'.

If you get a dwell, post back and we can walk you through the process.

 

Well so far it seems like I'm averaging about 16mpg which to me seems pretty low. I still haven't gotten a timing light but I'm talking to some friends of mine that may have one. Same with the dwell meter. Also the motor seems to always stall out after startup. Not just when it's cold but even after being at Full operating temp and only being shut off for 5 minutes. Which confuses me somewhat. Idle is about 500 - 600 RPM

 

Chances are it's not operating in feedback mode properly. Usually with a carb change you'll only need some tweaks with the IAB, or at most the Idle Mixture Screws, to bring it into a range in which the O2 sensor can start sending 'good' data to the ECM.

A dwell meter connected to the diagnostic lead near the blower motor will read the dwell for the Mixture Control Solenoid. Adjustments may need to be made to bring the dwell to 'around' 50% (six cylinder scale) at idle. The meter will also show you whether the dwell is properly 'ranging' in response to changes in mixture.

You should be getting close to or better than 20 mpg. Multiply what you spend on gas by 1/5 [(20-16)/20] and you'll get an idea what the savings could be.

 

Stalling when its cold is most likely a choke adjustment issue - it should appear fully closed when the engine is off and stone cold, and started up cold should be 1/8-1/4" open right away. Fast idle speed should be set between 1500-2000 rpm (within that range is the factory spec) and warm idle speed should be around 600-700 in drive, which is usually around 750-800 warm in park. The factory spec is around 500 in drive, but most engines are happier around 700 or so in Drive.

The stalling when hot issue, after it was shut off for a bit, sounds like a problem thats not uncommon to these cars, but isn't a problem with the carb itself (though it only applies to the carbureted cars). The problem is heat-soak in the fuel lines, because of the way its routed around the engine bay in these cars, and the fact that the carbureted cars only have a mechanical fuel pump. Because of this issue, GM started putting an electric fuel pump in the tank in addition to the mechanical pump on the block to give the fuel system a bit of a 'boost' to solve this problem. The carb itself is not the problem with this. I battled the same issue when I had the stock L69 (305 HO) in my car... once it started hot, just feather the throttle for a few seconds, kinda like how you would to keep a cold engine running without a choke, and it was OK after that.

If you are talking 16mpg around town, that sounds about right. The carbureted cars are usually in the 16-18mpg range around the city and mid-20s on the highway.

 

Yeah thats about what happens when i feather the throttle after I start it when warm. Idle seems pretty close to right except for the fast idle speed when cold, that is still really low at around 500 to 600 rpm in drive. I'll check the choke if I ever have a cold enough morning for it to do it again. My car doesn't stall on start up when it's about about 50 degrees.

And I'm getting anywhere from 14 to 17 mpg on average (calculated after mixed driving when i fill the tank) So thats both highway and city. Last night after alot of highway driving (anywhere from 55 to 75 mph) I filled it up and did the numbers and I average 17.4 I believe it was. So somewhere or another it seems I'm losing quite a bit of fuel economy.

 

15-17 i about what im getting too on my reman carb. If I Knew how to use the dwell and check/ set timming I would be all over it if there was a benefit of better mpg.

 

yeah thats what I'm thinking. I just need to get my hands on the timing light and dwell meter then I'll try my luck.

 

Im in the same boat. tell me how it goes.

 

Okay I just thought of something. Don't know if it could be part of my problem or not but I thought i'd bring it up. Could my AIR system not being hooked up cause my car to not operate in "feedback mode"? Causing my poor gas mileage or my lack of a torque converter lockup? Like my AIR system is all in place except 1 hose is unhooked from the check valve or whatever you would call it before the manifold, and the pump itself is seized so there is no belt on it obviously. Other than that it looks all there.

 

AIR system shouldn't affect mileage if it's disconnected. There's the remote possibility that a malfunctioning AIR system could, maybe, allow O2 into the exhaust manifold during open loop operation and 'mess' with mixture settings-causing a rich condition, but it would have to be pumping air into the plumbing for this to happen. Under normal operation it only injects air into the exhaust manifold plumbing during warm-up when the ECM is not operating in feedback mode.

I'll hunt an old post down later today that provides some good info on adjusting these motors, from setting timing to dwell.

 

well my AIR pump doesn't even have a belt on it, so no air flow there. I ordered a timing light from Harbor freight last night. I may end up getting a Dwell meter from there too in a few days if I can't find someone around me that has one. So hopefully I can atleast get the timing part done soon.

 

The A.I.R. system has no input for going to closed loop. The A.I.R. system is diverted based on open or closed loop mode. I don't know for sure about carb systems, but TPI will divert A.I.R. flow to the manifolds during certain closed loop conditions, and modifies the O2 tables during those times. Not having A.I.R. would lead to rich operation under those conditions. I don't think carb systems are affected, and even if they are, it isn't a big deal.

If you know somebody with a scan tool like Auto X-ray, you can use it to set the IAB as well. 50% MCS duty cycle is the same thing as 30 degrees dwell on the 6 cyl scale.

 

I ran into a small issue on the timing light thing. I can't seem to find a single place that I can see the timing marks on my engine. Everything is in the way of the harmonic balancer. And the few places I can see the balancer I can't see the pointer for the timing. And now that I have unhooked the vacuum lines from the AIR manifold and got a slightly better base timing by ear my check engine light comes on. I'm about to go get the codes off that though and I'll report back with what it says.

 

Your timing tab is probably at 12 o'clock, behind the water pump. Usually have to hold that evap control valve out of the way while pointing the timing light back there.

 

Is the mark a little circle tube like thing you can look through on the Timing chain cover? If so I found it.

Anyways the codes I got were code 14 "CTS - Temp HI" and code 24 "VSS" where should I look and what should i do to fix these issues. The VSS code really confuses the crap out of me because It's a cable driven speedo, and the speedo works fine.

 

The tube is for mounting a dealer test equipment probe. The tab should be close by. The mark is on the damper itself.

The VSS is on the back of the speedometer. It's a sensor for ECM input.

The CTS is on the thermostat housing.

 

Well the CTS is hooked up, the wires look a tad on the screwed up side like it needs a new connector baaaaddd. But it still seems to be working, if i un plug it the motor runs horrible and puffs smoke, when i plug it back in smoke goes away and the motor goes back to how it was before. And the VSS 1 how do i take the cluster out to look at it? And 2 what should I be looking for and how to do test it? Also would either of those being bad or not functioning correctly cause my TCC to not work properly?

 

The CTS is input for going closed loop, and the TCC doesn't lock in open loop. VSS is input for TCC lock-up, so if it isn't providing a signal, it won't lock up.

To remove the cluster, remove the face plate and steering column cover (under the dash). Loosen the steering column nuts that hold the column up (needed to get clearance to pull the cluster rearward). Remove the screws that hold the cluster in. Reach behind the cluster and push the clip that holds the speedo cable onto the speedo, pull the cluster out.

The VSS is a rectangular yellow plastic piece right by the speedo cable spindle.

 

So I should be replacing my CTS and my VSS then?

 

Troubleshooting at least. Input voltage is 5v. CTS high is a bit weird, not sure how you get there. Shorted CTS is one way, I guess.

 

that could make sense since my connector is pretty well destroyed. the 2 wires in the top were touching eachother and they were stripped at the part they were touching. I've separated them for the time being. But I need to find a place where I can get a new connector for it.

Is is there anyway to trouble shoot the VSS or is that something that I've pretty much gotta replace and pray?
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Just to be clear this is the CTS that I'd need to replace on the water neck correct? http://www.partsamerica.com/productd...pe=290&PTSet=A