1971 Plymouth Scamp ECS fuel tank vent

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badge94

badge94

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Hello A bodies Folks. We are looking for guidance/help with our 1971 Plymouth Scamp. We are installing our newly rebuilt 318 (built by Valley Performance.) Happy to report the engine make well over our 400 horsepower on the dyno (Edelbrock Heads, MOPAR performance valve covers.) In stock setup there is a collector on top of the passenger side valve cover that the evaporative emission control system (ECS) fuel tank vent line runs to. The new MOPAR performance valve covers do not have a vent. Any suggestions on how we can vent this line or what we could attach this line to?

From reading other threads we understand that this gas tank venting system is unique to the 1970 California cars and all 1971 cars. We are thinking about a way to safely/properly vent this line in the engine bay or possibly going to an earlier 69 style gas tank and fuel filler neck that just vents out the bottom rear of the car below the trunk.
 
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First have you made certain "it is" evap controlled? Do you have the extra vent line(s) coming out of the tank and (there may be) the separator can in the trunk? This system changed year to year, and I'm not sure ALL 71's had it. May have been a mid-year change.

So go back to the trunk, look and wrap your hand around the filler neck in the trunk, and see if there's a 1/4" vent tube going down the outside of the neck. If so you already have the older vent

If not, there's a couple of ways to deal with that depending on your creativity

LEAVE the 1/4" line going up into the engine bay, that IS THE VENT. Keep that line "high" in the engine bay to avoid siphon problems. Some guys advocate splicing that line into the filter bonnet or the valve cover breather (multi nipple) to help keep gas smell down

EDIT.............I did not see your second photo at first..........you could just branch the 1/4 tube coming forward from the tank into that breather
 
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as cast the mopar performance valve covers also dont have a filler hole, do they?

if your intent is to keep the evap system (and you should have a PCV system set up anyway) i would suggest taking the new valve cover, drilling the proper sized hole and installing the stock collector


of course, that is just one way to go about it



and welcome aboard, from the lakeshore
 
If you want to dupe the 70/ earlier non-evap system......go to MyMopar and download a 69 or earlier service manual and look up the vent. They are simple. The problem for the evap vs non evap cars is that the older cars--the filler tube went into the trunk first, then the tank, while the evap cars (generally) the filler tube was inserted from OUTside the trunk

This means if you weld a vent tube fitting into the filler tube, it must be "flush" like say a threaded fitting so you can insert the tube, then screw your adapter of choice into the tube after the filler tube is in place.

I have thought about experimenting with a nut.......braze it flush into the tube, then ream and tap for 1/8" NPT
 
67Dart273 said:
First have you made certain "it is" evap controlled? Do you have the extra vent line(s) coming out of the tank and (there may be) the separator can in the trunk? This system changed year to year, and I'm not sure ALL 71's had it. May have been a mid-year change.

So go back to the trunk, look and wrap your hand around the filler neck in the trunk, and see if there's a 1/4" vent tube going down the outside of the neck. If so you already have the older vent

If not, there's a couple of ways to deal with that depending on your creativity

LEAVE the 1/4" line going up into the engine bay, that IS THE VENT. Keep that line "high" in the engine bay to avoid siphon problems. Some guys advocate splicing that line into the filter bonnet or the valve cover breather (multi nipple) to help keep gas smell down

EDIT.............I did not see your second photo at first..........you could just branch the 1/4 tube coming forward from the tank into that breather
Click to expand...

Thank you for the input! Just to clarify, the second photo is of the old/stock blue painted valve cover prior to the engine rebuild. We don't plan on using the stock valve covers anymore, so the valve cover breather can't be used. Do you think it would suffice to just route the tube to the filter bonnet (by which I'm assuming you mean the air cleaner but please correct me if I'm wrong)?

Definitely want to try and minimize gas vapor in the engine bay. I've heard people talk about using charcoal canisters to do this, but not sure how something like that would be fabricated/installed. Any input on this would be appreciated.
 
67Dart273 said:
If you want to dupe the 70/ earlier non-evap system......go to MyMopar and download a 69 or earlier service manual and look up the vent. They are simple. The problem for the evap vs non evap cars is that the older cars--the filler tube went into the trunk first, then the tank, while the evap cars (generally) the filler tube was inserted from OUTside the trunk

This means if you weld a vent tube fitting into the filler tube, it must be "flush" like say a threaded fitting so you can insert the tube, then screw your adapter of choice into the tube after the filler tube is in place.

I have thought about experimenting with a nut.......braze it flush into the tube, then ream and tap for 1/8" NPT
Click to expand...

Thank you for the advice. Instead of modifying the existing filler tube, would it suffice to just source a filler tube and tank from a 69 or earlier A body? Seems like I might just be able to set aside the older tank and evap system that way, though it would require me to patch one hole in the trunk where that evap tube was and drill another for the vent tube that runs out to the frame rail and vents there, as on a 69 or earlier car. Any thoughts would be appreciated!
 
badge94 said:
Thank you for the input! Just to clarify, the second photo is of the old/stock blue painted valve cover prior to the engine rebuild. We don't plan on using the stock valve covers anymore, so the valve cover breather can't be used. Do you think it would suffice to just route the tube to the filter bonnet (by which I'm assuming you mean the air cleaner but please correct me if I'm wrong)?

Definitely want to try and minimize gas vapor in the engine bay. I've heard people talk about using charcoal canisters to do this, but not sure how something like that would be fabricated/installed. Any input on this would be appreciated.
Click to expand...
I've added a vapor cannister to my 71

Works great


But I maintain, you can simply punch out a hole in that fancy new valve cover and run the stock breather
 
diymirage said:
I've added a vapor cannister to my 71

Works great


But I maintain, you can simply punch out a hole in that fancy new valve cover and run the stock breather
Click to expand...

Any chance you can send a picture of your vapor canister setup (when you have chance) and tell us what unit your using?
 
Johnny Dart said:
That's a Big ....... ONM
Click to expand...

@Johnny Dart can you post some pictures of the setup in your 70 Dart? I've seen the setup in 69-70 service manuals, but the pictures those have are not clear on how the vent line runs through the floor of the trunk or where the line terminates. I've heard some say that the line terminates inside the frame rail, is this what your setup is like?

@SGBARRACUDA I am interested in the filler tube. Can you email me about a price and send a photo?

[email protected]
 
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