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CarburetorsCarb discussion and questions. Upgrading your Third Gen's carburetor, swapping TBI to carburetor, or TPI to carburetor? Need LG4 or H.O. info? Post it here.
Hey ThirdGen,
So I'm in the process of restoring my car. When I bought it, it was essentially a collection of mismatched racing parts heaped into an 83 Z28.
I just picked up an original CC Quadrajet and intake manifold, and I am now trying to locate all of the pieces I'll need to get this bad boy running.
I've been searching through old posts trying to find out specifics, but for the most part people are interested in removing the quadrajet, rather than putting it back on the car.
This is what I have so far:
-An E4ME Quadrajet
-A Large Cap 7-pin HEI
-An ECM for this application
-A BARO sensor
-An 02 sensor
Maybe others, but I need to look through this hack job wiring harness.
Questions:
Which other sensors do I need?
Do I need a Knock sensor? Somewhere I read that that feature was not available until '84 or '85, is that true?
I have a clutch style fan, do I need the fan switch still?
My car came with headers with 02 bungs that are smaller than stock. They probably won't be on the finished product, but could I use them with a smaller 02 sensor while testing everything?
Can I pull compatible sensors from other Third Gens?
Are there sensors worth replacing right off the bat?
You probably don't need a baro sensor; AFAIK that wasn't on 49-state 83 cars.
You don't need a knock sensor unless it's a L69. (VIN code 7; if your car is VIN code H, then it's LG4, and didn't use it that year)
Again, no fan switch unless L69.
Never heard of different sized O2 sensors. But yes, if you have such a thing, use what fits.
You will need a coolant temp sensor, MAP sensor, VSS buffer (yellow box on the back of the speedo); in addition to the gauge sending units (water temp, oil press) and the electric parts in the carb (choke, TPS, MCS). There are other parts & pieces as well, that aren't "sensors"; the EFE TVS (you'll need a EFE valve as well whenever you put manifolds back on if that's your plan), purge control valve, purge TVS, AIR diverter valve (again, if you put manifolds back on). A cat of course.
No sense whatsoever in using used sensors. They're not very $$$ at all. Get new.
Hacked-up wiring is always a PITA. Fortunately once you identify the various wires, it shouldn't be too hard to get connectors off of other cars at the buzzard nest. They don't have to be the same sheet metal; Caprices used the exact same LG4 as our cars for example.
Thanks sofa. That's perfect.
It's a Vin H, which makes things more convenient oddly enough.
I believe there is a BARO sensor, just because it's where one would be, and says BARO on it. Maybe there's a story there.
I'm going to run through that harness when I get the chance. It might be time to finally suck it up and buy that shop manual.
Thanks again
California cars may have had a baro sensor that year. For that matter 49-state ones might have, can't recall. If memory serves the connector will be a 3-wire in-line Weatherpak with a bright green body, same color as the one-pin dwell test connector over by the blower motor.
It should have a BARO sensor. And a VAC sensor (manifold vacuum).
The only other things it NEEDS to run are the TPS and MC solenoid connections on the carb (and a wire to the electric choke). The O2 sensor. And, of course, the ECM connection hanging out the back of the computer controlled distributor.
EVERYTHING else can go and the ECM will be none the wiser. All those air injection lines and hoses, all the charcoal canister lines, the EGR system.... all of it. I would leave a functional PCV valve system, though, just to keep the valve covers clean.
Most people do this just to "clean up" the look of the engine bay, but in your case you're just looking to hook up the bare minimum of computer sensors and components to make it run without the ECM freaking out. And that's what you need to do it.
Thanks Damon, that's good to know.
So I ran through everything, and I think I found most of what I need. Still, I'd appreciate it if you could check my work.
I think this is the BARO sensor. It's on the driver's side firewall, in the back right corner and high, if you're looking from the front.
I'm not sure if this is all of it, but I think this is most of a PCV setup I pulled from a L69 engine I pulled apart a while ago. We got the elbow, the pcv valve, and this other little piece that looks like a check valve of some kind. Not sure how it all fits together. An explanation of what all this does and why it keeps valve covers clean would be nice. Something about crankcase pressure.
An EFE TVS that came off the same engine. It's still attached to the waterneck. I think the thing on the bottom is temp sensitive, based on the fact that it's copper. What does it do? What does it connect to? I read an explanation by sofa on another thread. Something about engine temp and exhaust recirculation. Definitely witchcraft.
Mystery sensors. I think one is a fan switch, one looks like it hooks up to Vacuum, the other is just a mystery
Questions:
1) Where is that VAC sensor, and why do I have both that and a BARO sensor?
2) All of this stuff is going on a late model TPI engine. It does have a sensor in the driver's side head for one of the guages. Can I use that?
3) Is there a significant difference between TPI exhaust components and the ones original to my car? I have AIR components for both, but the TPI ones are in better shape.
Pic 1 is the MAP sensor. It measures manifold absolute pressure. That's why it has a vac line... a baro sensor, which measures the ambient barometric pressure, doesn't need that. "Vacuum" is the difference between the 2... the baro sensor is only used to fine-tune the ECM's measurement of vacuum (engine load) as the barometric pressure changes, such as from altitude.
Can't tell what #2 is. Looks like part of something that's broken. Whatever it is/was, it isn't anymore, and isn't any good for anything.
#3 is the fitting where the vacuum line plugs into the brake booster.
#4 looks like a PCV valve with some extra stuff attached to it. Nothing of any value.
#5 is a water outlet, with a vac fitting for the A/C and cruise in a 5-spd car that belongs on the top of the intake manifold right behind the carb, stuck in th ehole where the coolant temp sensor goes. You're right, the other thing is the EFE TVS (Thermal Vacuum Switch for the Early Fuel Evaporation system). #6 is the reverse view.
#7 is the aforementioned A/C & cruise fitting, a broken temp thing of some sort probably a temp gauge sending unit, and the remains of either a fan switch or a coolant temp sensor, depending on whether it has 1 pin or 2.
I'm going to guess that you're taking the TPI off and putting your carb setup on? In that case, whatever is left after the TPI is gone, can be used with your carb. (temp gauge sending unit in the driver's side head included)
As to the exhaust question, I'd have to see both setups side by side in detail to comment on that. They won't be the same but some adapting may be possible.
In a CC-QJet application the sensor with the vacuum line on it is a VAC sensor (MAP sensors look identical but their voltage output is exactly OPPOSITE of a VAC sensor and not interchangable). The BARO sensor has NO vacuum line on it (just a vacuum nipple hangin' out in the breeze), looks physically identical to the VAC sensor and works as Sofa says. In other words, you should have two identical looking sensors on the firewall near the power brake booster- VAC and BARO.
Let me take a stab at what you're seeing in the pics. Mostly agreed with Sofa, but it can be tough to tell from internet pics, so I'm just going to shoot from the hip here. Either one of us could easily be right (or wrong) about some of this.
Pic #1- VAC or BARO sensor- can't tell which. Gotta figure that out, as I mentioned above.
Pic #2- Not sure.
Pic #3- Vacuum brake booster check valve- pushes right into the grommet on the front of the brake booster
Pic #4- PCV valve with original hardline which has now, obviously, crumbled. Replace hardline with standard 3/8" vacuum line.
Pic #5- Thermostat housing. Sensor on the right is, I believe, part of the evap/charcoal canister vacuum system. Refer to "vacuum routing diagram" in the sticky in this forum to figure it out for sure. That thing on the left doesn't belong there- there should be another thermal vacuum switch very much like the one on the right.
Pic #6- Underside of T-stat housing, as above.
Pic #7- From left to right... Vacuum fitting that goes into the intake manifold behind the carb and supplies vacuum to the HVAC vacuum reservoir. Coolant temp sensor that runs the gague on the dash. Knock Sensor.
Side note- some of that stuff doesn't look like it came off a V8 L69 motor, most notably the PCV stuff and the thing in pic #2.
Pic 1 is a MAP sensor... vacuum line clearly visible. Plus, it's on a bracket against the firewall right immediately above the bulkhead connector, not hung under the edge of the cowl over above the heater lines like a baro sensor would be. And the bonus plus... the connector is black, not bright green.
TPI exhaust manifolds are different in a couple of important ways.
TPI manifolds are larger in diameter and will flow better than LG4 manifolds.
TPI manifold on pass side has a longer sweep down and will not mate to the LG4 Y.
TPI manifold on drivers side will have the AIR pipes facing to the rear. LG4 to the front.
TPI manifold on pass side will have the AIR pipe check valve located about 2 inches lower than the LG4. This can still be plumbed to the AIR pump but will require some elbows instead of the straight piece of hose the LG4 uses.
TPI manifold on pass side uses a solid spacer (well, hollow inside) between the manifold and the y pipe, but the EFE valve used by the LG4 will fit.
Adapting the TPI manifolds to the LG4 system isn't terribly difficult, easier if you're abandoning the AIR system, but still doable. The TPI specific Y pipe will have to be used and cat/cat back specific to the TPI model/year is needed.
Early TPI used the L69 style manifolds and Y and I assume, but have no experiential knowledge, that the orientation of the AIR pipes is still an issue. L69 Y is identified by the four-bolt flange to cat.
I've always considered the pressure sensor on the LG4 to be a measurement of gauge pressure within the intake tract, with the input from the barometric sensor used to convert this to absolute pressure (somewhere within the black box we call the 'ecm'.
That thinking led me to always refer to the pressure differential sensor next to the brake booster as a 'vacuum sensor' and not a MAP sensor. I am, however, open to change.
Alright alright. This is all great stuff. I just wish I had more time and money.
Sorry guys, I should have asked that exhaust question more clearly. I don't have a y-pipe at all yet. I have 2 sets of manifolds; one for a 305 tpi, and one for the l69. I can get either y-pipe pretty cheaply, I just wanted to know if one was better than the other.
I'm confused about the exact location of that BARO sensor, I think I'm confused about something simple. Can you guys explain it to me like you would to a child?
L69 exhaust (with Y) is best IMO, but the factory Y is hard to come by. L69 AND TPI manifolds will both connect to the TPI Y pipe. The TPI Y pipe is not as robust as the L69 Y but will support the installation of a factory style 3" slip on converter which will expand your choices for an aftermarket cat back system. (The L69 converter has a four-bolt flange on both ends.)
Baro sensor is on pass side, mounted to cowl and will NOT have a vac line attached.
Yes. L69 manifolds with TPI Y pipe. The L69 manifolds will have the AIR tubes in the correct orientation and the TPI Y will provide less expensive options for cat converter and cat back.
Hey guys,
So I've spent a while trying to find that BARO sensor. I'm kinda embarrassed to admit that Im having trouble, especially with so much help.
You guys gave me great instructions, but I'm way out of my league here, and honestly most of it went clean over my head.
What I did get was:
-On the Firewall
-Connector is Bright Green
-Should be Identical to the MAP or VAC sensor, but with no Vacuum line.
I took pictures of everything green in the enginebay. If you guys get a chance, maybe you can identify them. I don't mind buying a new one if it's gone, but I also don't want to own 2.
Here goes nothing:
1) I don't know why, but this picture was cropped strangely. This is the most noticeable green piece in the engine bay, and seems like the right size. It's due north if you are looking from the front bumper. It's also a circuit board totally exposed to the elements, which weirds me out, but we'll cross that bridge later.
2) This seems like the connector sofa mentioned.
3) I think this is the one pin dwell tester connector
Questions:
I feel like this has been answered, but do I need both the MAP and BARO sensors for this Carb to run well enough for me to check for other problems?
A local guy is selling a carbed camaro intake that came from the factory for use with center bolt heads. Is it worth it to spend a few bucks on it, or should I modify the stock intake? I've heard mixed opinions. Will it look clean after modification?
#1 is the wiper motor. Not sure what exactly the green part on it is. There's supposed to be a black plastic cover over all that stuff in the pic (the PCB etc.)
#2 looks like the connector from the ECM to the distributor but it's hard to tell for sure.
#3 is indeed the Mixture Control Solenoid dwell test connector. If you have a baro sensor its connector will look exactly like the one for the MAP sensor in the pic further up, except the body of it will be that same green plastic.
If you have a baro sensor it will be mounted under the lip of the windshield cowl, i.e. only about an inch below the underside of the hood, about directly above the pass side valve cover. If your car didn't come with it, you don't need it. I really don't think you have it; it's not mentioned in my 83 FSM, and I don't recall ever seeing one in a car before 84.
There's no benefit to that other intake, if it's a factory one, over the factory one you already have. (assuming you have it?) Alternatively you could get a Performer, which these days is virtually identical to the ZZ4 one; it bolts right up to everything under your hood.
A trip to the quarter car wash would REALLY do your engine compartment ALOT of good. I don't see how anybody can work on anything that's THAT groaty.
In naf's 2nd pic, I'd bet that the baro sensor connector is laying up against the dist cap... that thing right there sure does look like a whole lot like it.
In that pic of the 84 I was in the process of installing TPI manifolds, the baro connector has been tucked away and the AIR system moved over. It's since been put back together but I am swapping in a new radiator today. If any pics are needed, just let me know.
It's the closest one to stock that I have, although a keen observer will note several year specific differences from the original 84 LG4.
Yeah, I don't think I have that, I'll double check when I'm home.
As for the factory Manifold, the only advantage is that I could use it without having to alter it to fit my heads.
I have to get it running before I can bring it to the wash. Besides, if I washed it I wouldn't recognize anything
I'm going to throw everything on the engine that's in the car now and see if I can get it to start. I always assumed it was broken, because that's what I was told when I bought it, but now I'm starting to wonder. Seems worth a shot.
keep us in the loop. I've converted a handful of these back to the ccc-qjet system over the years. Pieces/parts are getting much harder to find nowadays though. Used to be able to grab handfuls of stuff at the local pullapart. They haven't had a thirdgen in the yard all Summer though.
Yeah our cars are REAL TOUGH to find in the buzzard nests these days; but there's lots of other vehicles you can go to for LG4 parts. Caprice, Monte Carlo (and the other divisions with the same chassis that put LG4 in them), trucks, etc. Figure out which are the same (most) and which are different (not many), and what parts aren't worth ganking off the buzzards to begin with (sensors for example), and then it's not as tough to scab one back together.
Yeah our cars are REAL TOUGH to find in the buzzard nests these days; but there's lots of other vehicles you can go to for LG4 parts. Caprice, Monte Carlo (and the other divisions with the same chassis that put LG4 in them), trucks, etc. Figure out which are the same (most) and which are different (not many), and what parts aren't worth ganking off the buzzards to begin with (sensors for example), and then it's not as tough to scab one back together.
That sounds good. I'm lucky that I have most of the pieces. There are no pull apart yards in CT ( I think it's a state ordinance or something) and very few scrap yards have anything older than 10 years.
09-13-2015, 10:23 PM
Plus, it's on a bracket against the firewall right immediately above the bulkhead connector, not hung under the edge of the cowl over above the heater lines like a baro sensor would be. And the bonus plus... the connector is black, not bright green. 
