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1970 Cutlass now with 455. I am installing a new aftermarket fuel tank and would like to run a new line as a vent to the front of the car. It would go to a charcoal canister that doesn't exist in the car yet.
Question, has anyone added a vapor vent line with charcoal canister for vapor purge into the engine when first starting? I am trying to make this 70 Cutlass more modern as far as gas vapor smell in the garage is concerned. Since the car did not have this originally, I was wondering if anyone else has done this on a car that never had it before. I would like to get some info on others' experience(s) on how they did this (part #'s/apps/successes, etc.). I have some ideas, but wanted to get some input.
TIA,
You should be able to use the same parts from a 71-72 Cutlass. The CSM will show the assembly. I’m sure someone can post those pages from the CSM to help out. Joe? Norm?
I guess my question doesn't really matter since "evidently" you don't have a fuel canister; yet, 1970 vehicles came w/ a fuel vapor canister. So, you have no fuel vapor canister where one originally existed. Is this correct?
1970 seems to be a crossover year. There was no vent line from the tank to the engine bay (only a fuel supply line) and there definitely wasn't a canister in this car originally. I think it depends on what state emissions had to be met (like a Cali car vs. 49 state) for 1970. There was no evidence of a canister or its mount anywhere. And the original tank I just removed had this that goes nowhere:
I'll start looking in my 1970 manual and PIM to see if I can find anything. In the meantime, maybe someone who has knowledge of this particular subject in this crossover year can chime in on what cars got what.
In my general internet reading, it seems that 1970 was a year that evap systems started to be generally incorporated, but not necessarily on everything...
The 1970 fuel vapor vacuum canister (Option 35NA9) assembly is located on pages 8-132, 8-134, 11-134, 11-136 in the 1970 PIM (most likely in the CSM, as well). I haven't done what you are attempting, but think I would ensure if you attempt to retro-install a 1971-1972 fuel vapor assembly system you evaluate the type of canister (from a 1971/1972) and the type of air breather/cleaner (from a 1971/1972) are compatible with your style of air breather. I might be mistaken, I'd have to do some navigating, there may have been two styles of fuel vapor canisters in the 1971 &/or 1972 model years. Hopefully you'll find others who are experts to assist you. Good Luck!
Evaporative Emission Controls were required in California on cars sold after January 1, 1970. The option code for the controls was NA9; it was a mandatory option in CA in that time-frame.
The NA9 equipment included a different fuel tank with a fill neck that would accommodate a non-vented fuel cap. There was a vapor line from the tank to a carbon cannister behind the passenger-side headlights.
The cannister for 1970 had three hoses. One was the vapor inlet, another teed into to the PCV hose to pull vapors out of the cannister when the car was operating, and the third took fresh air from the air inlet on the air cleaner.
An information label was placed above the Tune-Up label. Oldsmobile's label was black and red print on a yellow background.
The only maintenance requirement was a periodic change for the filter located on the bottom of the cannister.
In 1971 and later, the cannisters had only two hoses (the fresh air hose was eliminated), but the operating principle was the same.
The canister was only one part of the evaporative emissions system on the '71-'72 cars. There was also a standpipe located behind the rear seat that would allow fuel vapors to condense back to a liquid state and return to the gas tank. To properly convert your car without the charcoal canister, you would need to add the standpipe as well. The standpipe had 4 tubes that exited the bottom; two 5/16' tubes collected gas vapors from the tank, a 3/8" tube allowed the condensed fuel to return to the tank and a 5/16" tube that followed the passenger side frame rail to the charcoal canister mounted on the radiator support. I did an EFI conversion with an in-tank fuel pump using a resto-mod tank from Rick's Tanks. I wanted to retain the emissions system so I made the following diagram to work out the fittings and connections required. I hope this helps.
The standpipe is a nice addition but not strictly necessary. I don't know if the '70 body stamping has the void for it, and you'd have to get one from a donor car. You can pull straight from the vent connection on the tank to the canister.
The modern service replacement charcoal canisters have a slightly different connection setup. The fresh air inlet is now just an open fitting with a little cover that stops rocks from going into it. You don't need to run a hose to the air cleaner.
Most important thing is to make certain the vacuum that pulls from the canister is restricted with a small hole, something like 0.040". You can drill a hole in a small pipe plug and shove that in the hose. Ideally it's a ported vacuum - you don't necessarily want it pulling from the canister at idle.
It may be tempting, but don't use an old canister. There is - literally - a cloth bag of charcoal bits inside of it. The bag deteriorates over time. It's not uncommon for a car to try to suck all the charcoal out of the canister.
The standpipe, it seems, is to keep liquid gas out of the line to the canister and also allow any condensed liquid back to the tank. I think I am going to do it similar to the 80s Cutlasses and just run a line up high from the vent over the rear axle part of the frame and then down to the frame rail up to the front of the car. Maybe run it next to the fuel supply line the whole way. I was thinking of also running a line from the air cleaner to tee into this vent to the canister to minimize the vapor from the carb itself. The purge will go to ported vacuum with the aforementioned line restriction.
Should this setup also have a purge valve? Under what conditions would a purge valve be activated?
Last edited by rfpowerdude; Apr 1, 2024 at 02:36 PM.
Do you have a non-vented gas cap on your car? Years ago I decided I wanted a locking cap for my 1970. I mistakenly got a vented cap, and when the tank was full it would slosh gas out through the vent in the cap. I agree with oldcultass, if your getting a strong gas smell something is wrong.
A purge valve can be used to make sure the purge only happens when the engine is hot and it's at cruise: above idle and have high vacuum. ECU cars easily have that logic. Carb cars just run it on ported vacuum and call it good enough.
Previous to the requirement for vapor recovery, everything was just vented to the atmosphere. Tank vapors and carb vapors were not contained at all. Drive home from work in the summer for 30 minutes and pull into the garage in Florida and then come back out an hour later and the garage has a gasoline smell due to vapor from a hot carb AND somewhat hot gas tank (ambient over asphalt can get damned hot).
I just want to contain this to a large degree and it seems like it would be easy enough with the addition of a line from the tank vent up to a charcoal canister added up front. Then a restricted vacuum line to a ported vacuum source and DONE.
Drive home from work in the summer for 30 minutes and pull into the garage in Florida and then come back out an hour later and the garage has a gasoline smell due to vapor from a hot carb AND somewhat hot gas tank (ambient over asphalt can get damned hot).
Same situation in S. Texas. That's how cars reacted to heat before 1970 or so. Those who say there is something wrong may not live in hot climates.
No, I did not, however, when the time came, I was going to contact a few people on here to find out if they had any parts. Rick is one of them. Nick is another.
Thanks for looking for me Norm!
You stated you have the 1970 PIM...here is the 1971 & 1972 ASM V-8 Canister ASM locations. The obvious delta being the three hose (1970) vs. two hose (1971/72) applications.
The nice diagram Rodney created, with the Standpipe, represents the 1971 and later NA9 EEC systems. Fitting the Standpipe to your 1970 will require cutting a slot in the trunk pan behind the rear set. As I recall the Standpipe has a flange with gasket that attached to the trunk pan via sheet metal screws. The 1970 had a small black plastic multiport Separator, instead of the Standpipe and hence no opening slot, that was secured via carriage bolts to a bracket spot-welded to the underside of the trunk pan, forward of the tank. The 1970 PIM page 8-120 illustrates it.
I have a 1970 Chevelle with NA9, which was required in California. However the car was ordered by the local dealer, here in NY, for their sales inventory. I can't imagine why they checked off NA9 on the order form.
Hey Rodney, what vacuum port from the EFI did you use to hook to the charcoal canister? And did you use anything special to cap the unused vapor port on the tank?
setting up a sniper on my 71 and I want to keep the canister
thanks!
Originally Posted by cdrod
The canister was only one part of the evaporative emissions system on the '71-'72 cars. There was also a standpipe located behind the rear seat that would allow fuel vapors to condense back to a liquid state and return to the gas tank. To properly convert your car without the charcoal canister, you would need to add the standpipe as well. The standpipe had 4 tubes that exited the bottom; two 5/16' tubes collected gas vapors from the tank, a 3/8" tube allowed the condensed fuel to return to the tank and a 5/16" tube that followed the passenger side frame rail to the charcoal canister mounted on the radiator support. I did an EFI conversion with an in-tank fuel pump using a resto-mod tank from Rick's Tanks. I wanted to retain the emissions system so I made the following diagram to work out the fittings and connections required. I hope this helps.
Choose a vacuum port with constant vacuum (not ported vacuum, which varies with throttle position). Use a vacuum gauge to check that you have found a correct port.
thanks! Wanted to make sure having a constant vacuum wouldn’t mess up the fuel map at idle by pulling in the vapors from the canister. Not to hijack the thread, but any tips on changing out the charcoal? I read you can get some activated charcoal from the pet store. Anything you found that works better than others?
Originally Posted by VC455
King...
Choose a vacuum port with constant vacuum (not ported vacuum, which varies with throttle position). Use a vacuum gauge to check that you have found a correct port.
King:
I used a 3/16" ported vacuum port on the throttle body. I was concerned about poor idle quality so the ported source seemed to be the more favorable option as it's only active off idle. I kind of guessed at the restriction size; I filled a 3/16" to 1/4" hose barb with epoxy then drilled a 1/16" hole through the epoxy. I haven't had any complaints about gas fumes in the garage so I guess it's working well.
I'd recommend using ported. In modern cars, the charcoal canisters are only vented at mid-throttle and after the engine warms up. Definitely want a restriction - at least the modern replacement canisters might not have any restriction in the canister itself. I went real small, something like 0.040".
You don't need much air flow at all. Remember this is just to pull gas vapor out of the charcoal that gets collected in there. Unlike modern cars that are nearly sealed, this just pulls air through the canister - it doesn't actually pull air from the tank or try to put a vacuum on the tank.
A plain rubber cap is fine for the tank, don't even need a clamp as long as its a good fit. It should rarely see gas, but check it every few years just like checking the fuel lines.
