Vapor hose routing/new 3rd gen owner
04-07-2017, 12:43 AM
#1
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Car: 1984 Trans Am
Engine: LG4 305 4bbl
Transmission: 700R4
Axle/Gears: 3.23 LSD
Vapor hose routing/new 3rd gen owner
Hi all from rainy NZ 
I've been a bit of a lurker since getting my 84 TA in January this year. I've learned a bit from the goldmine of info here!
Anyhoo, my 84 has been in New Zealand since 1988 and has long since has most of the smog gear removed as we have never required it by law.
Apart from that and a set of headers (extractors), it is all bone stock LG4.
In 2016 the last owner replaced the carb with another rebuilt unit from Sean Murphy Induction in CA as he could find no-one he felt trustworthy to rebuild the original here. I ran the number (17082204) which appears to be from a 1982 Chev 305 with AC and AT.
The car initially came with the hose from the gas tank to the canister with the valve in between, but the smaller port above the valve had nothing attached to it. Did this have a hose going to a tee coming from the PCV maybe (see pic)? I changed to a straight hose only with no valve.
The other is just a straight hose going from the canister to the vent tube at the carb. The vent tube was also capped off when I got it but have been told by some that it should not be capped at all. There was nothing going from the carb port on the canister when I got the car.
I only did this today, not driven it yet.
Pix 1, 3 and 4 are how the car came. 2 is what I did today and asking about.
Any thoughts?
Cheers
I've been a bit of a lurker since getting my 84 TA in January this year. I've learned a bit from the goldmine of info here!Anyhoo, my 84 has been in New Zealand since 1988 and has long since has most of the smog gear removed as we have never required it by law.
Apart from that and a set of headers (extractors), it is all bone stock LG4.
In 2016 the last owner replaced the carb with another rebuilt unit from Sean Murphy Induction in CA as he could find no-one he felt trustworthy to rebuild the original here. I ran the number (17082204) which appears to be from a 1982 Chev 305 with AC and AT.
The car initially came with the hose from the gas tank to the canister with the valve in between, but the smaller port above the valve had nothing attached to it. Did this have a hose going to a tee coming from the PCV maybe (see pic)? I changed to a straight hose only with no valve.
The other is just a straight hose going from the canister to the vent tube at the carb. The vent tube was also capped off when I got it but have been told by some that it should not be capped at all. There was nothing going from the carb port on the canister when I got the car.
I only did this today, not driven it yet.
Pix 1, 3 and 4 are how the car came. 2 is what I did today and asking about.
Any thoughts?
Cheers
Last edited by NZ84TA; 04-07-2017 at 12:47 AM.
04-07-2017, 12:16 PM
#2
Supreme Member
Re: Vapor hose routing/new 3rd gen owner
Welcome from rainy CA!
I don't know if you have any repair references to the Evaporative Emission Control System; I've attached the pages from the '87 FSM. Hopefully, it will be similar to the '84 model year.
I don't know if you have any repair references to the Evaporative Emission Control System; I've attached the pages from the '87 FSM. Hopefully, it will be similar to the '84 model year.
Last edited by paulo57509; 04-07-2017 at 12:19 PM. Reason: Poor grammar.
04-07-2017, 03:00 PM
#3
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Car: 1985 Trans Am
Engine: LG4
Transmission: 700R4
Axle/Gears: 3.08
Re: Vapor hose routing/new 3rd gen owner
After looking at your photos and looking at my car, you have it plumbed as best it can be given the circumstances. The purge valve would connect to the Canister Control Valve (CCV), which you don't have. The plugged fitting off the PCV would also go to the CCV. So because there is no longer a CCV, you have it plumbed direct to the canister.
The first photo shows the CCV and the second photo just shows the carburetor. The CCV would be at the bottom of that photo.
The first photo shows the CCV and the second photo just shows the carburetor. The CCV would be at the bottom of that photo.
04-07-2017, 03:06 PM
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Car: 1985 Trans Am
Engine: LG4
Transmission: 700R4
Axle/Gears: 3.08
Re: Vapor hose routing/new 3rd gen owner
This photo shows the CCV with its associated plumbing. If you want the Evaporative Emissions Control (EECS) to work properly, you will need this. Otherwise the charcoal may become saturated because of so much vapor.
04-07-2017, 06:02 PM
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Car: 1984 Trans Am
Engine: LG4 305 4bbl
Transmission: 700R4
Axle/Gears: 3.23 LSD
Re: Vapor hose routing/new 3rd gen owner
Thanks heaps guys!
I never thought of the possibility of saturation, that would ultimately mean fuel itself leaking from the canister, right? And an awful smell under the hood.
Right now there is no smell or leakages at all.
As I have no CCV, could I run a hose from the small fitting at the top of the purge valve to a line tee'd from the PCV (see pics)? I assume that line would've been the one that draws vapors back out of the canister (vacuum) into the chamber for re-burning? Is that about right?
As for the hose coming from the carb, should I just attach a small filter at the canister end, rather than have it connected?
Is the tank still venting with just the tank line hose connected to the canister? Does it vent out the other port or out the bottom? (see pic)
Sorry for the 20 questions, knowledge of these systems is almost nil here!
Cheers and thanks again!
I never thought of the possibility of saturation, that would ultimately mean fuel itself leaking from the canister, right? And an awful smell under the hood.
Right now there is no smell or leakages at all.
As I have no CCV, could I run a hose from the small fitting at the top of the purge valve to a line tee'd from the PCV (see pics)? I assume that line would've been the one that draws vapors back out of the canister (vacuum) into the chamber for re-burning? Is that about right?
As for the hose coming from the carb, should I just attach a small filter at the canister end, rather than have it connected?
Is the tank still venting with just the tank line hose connected to the canister? Does it vent out the other port or out the bottom? (see pic)
Sorry for the 20 questions, knowledge of these systems is almost nil here!
Cheers and thanks again!
04-08-2017, 04:59 AM
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Car: 1984 Trans Am
Engine: LG4 305 4bbl
Transmission: 700R4
Axle/Gears: 3.23 LSD
Re: Vapor hose routing/new 3rd gen owner
Here's what I've done. Hose between carb vent bowl and canister has been removed for now.
As I understand it, that little valve closes when the car is shut off, and opens when running so the vapors going through the tank vent line must carry some small amount of pressure to open it in order for the vapors to get to the canister, correct?
I don't know if any vapors escape through the now-unused carb port?
Anything I've missed (or wrong lol)
Cheers
As I understand it, that little valve closes when the car is shut off, and opens when running so the vapors going through the tank vent line must carry some small amount of pressure to open it in order for the vapors to get to the canister, correct?
I don't know if any vapors escape through the now-unused carb port?
Anything I've missed (or wrong lol)
Cheers
Last edited by NZ84TA; 04-08-2017 at 05:38 AM.
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05-04-2017, 09:35 PM
#8
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Car: 84 TA orig. 305 LG4 "H" E4ME
Engine: 334 SBC - stroked 305 M4ME Q-Jet
Transmission: upgraded 700R4 3200 stall
Axle/Gears: 10bolt 4.10 Posi w Lakewood TA Bars
Re: Vapor hose routing/new 3rd gen owner
This is your lucky day. 
I also have an 84 TA LG4 305 and will be removing the emissions crap - except for the fuel tank venting and charcoal canister. The ECM and CCC carb will also be removed and I will be using a 1904 Edelbrock manual QJet carb. I've spent many hours figuring out how to connect this. And you will now benefit from my research. Here is what I came up with:
(the XJW modified diagram is what I am going to follow)
I also have an 84 TA LG4 305 and will be removing the emissions crap - except for the fuel tank venting and charcoal canister. The ECM and CCC carb will also be removed and I will be using a 1904 Edelbrock manual QJet carb. I've spent many hours figuring out how to connect this. And you will now benefit from my research. Here is what I came up with:(the XJW modified diagram is what I am going to follow)