FUEL TANK QUESTIONS - 1970 Roadrunner

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HI Guys - Back to the questions on the 1970 roadrunner I am working on for a buddy. I removed the stock original fuel tank and need to replace it with a new one. The original had four vapor lines going to a cannister. Im doing a restoration that is not 100% stock, is it necessary to replace the tank with one that has the 4 lines to the cannister or can I just use one that does not have them? Al Gore doesnt live in my neighborhood and we dont have a smog test in my state, so is all the extra smog stuff really necessary?

The car has a 383 engine and I see photos of some additional fuel / smog cannister on the passenger side down by the fuel pump? Is this necessary? Im thinking I just use a tank without all the vapor stuff and run a fuel line straight to the stock mechnical fuel pump and then direct to the holley 750. I dont see a need to run a return line to the fuel pump.

Any advice? Reasons I cant do it this way? Advice on where to source a new fuel tank? Anything Else Im missing?

Lots of questions - thanks for lots of answers.

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[HawkRod]

Hi,


The California cars had the Clean Air System(CAS). Fuel traveled to the motor in the conventional way, from the sender through a line to the fuel pump and into the carb. OK, easy.

The CA cars had a Holley carb that had a fuel bowl vent line. This line went from the carb to breather on the passenger valve cover. This breather has three connections. One to the air cleaner, one from the carb, and the third connected to the return line. The return line went back to a metal tube type canister that was mounted in the trunk on the passenger side. This return line went into the canister. The canister then connected to the fuel tank via four lines.

The intent of this system was that fuel vapors could make their way to the canister from either the engine or the tank. When they condensed, they would flow back to the gas tank.

Bottom line: If you do not want to keep the CA system, then all the return stuff can be removed. No harm, no foul.

Note, however, that the CAS tanks are available and cost no more than a regular tank. If you are replacing the tank anyway, why not hook it up? It really doesn't hurt performance. Even if you don't fully hook it up at the engine, the parts will still be there if anyone ever wants to hook it back up as original.

Hope this helps,

Hawk

In this picture, the open connector on the breather obviously goes to the air cleaner. The hose on the left goes down to the return line and the canister in the trunk.

 

[short stack]

Ahhhemmm. Black out in engine compartment??? I thought you lost all forum priveleges with that?? Bwaahahahaaa ( I wanted to do the same to the car Im working on, but got bitch slapped in my welcome thread for even considering it!) I see you dont have a heater installed, so I will cut you some slack brother.

Anyway - Ok, I hear you on doing it the right way, just thought all the vacuum lines from the gas tank to the cannister in the trunk just was opening up more possiblilties for "gas smell" or other issues that mopar was trying to avoid back in 1970. I was just trying to eliminate issues - I guess I should ask: Using a factory block mounted mechanical pump, do I need a return line? I plan on using a holley 750 and edelbrock 383 manifold. I figured that a stock fuel pump was matched to that holley carb and I would not need a fuel regulator OR a fuel return line.

Is that an incorrect assumption?

Thanks for the photo of your engine, makes more sense as to what the return line to and from the breather looks like. I dont plan to use that either btw.


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[HawkRod]

Ahhhemmm. Black out in engine compartment??? I thought you lost all forum priveleges with that?? Bwaahahahaaa ( I wanted to do the same to the car Im working on, but got bitch slapped in my welcome thread for even considering it!) I see you dont have a heater installed, so I will cut you some slack brother.

For the record, I am now in the process of FIXING the black out in the engine compartment, since some dork changed the color of the car and subsequently sprayed the engine compartment black (and he did a crappy job too). Since I am repairing what has been "Chevy-ized", the forum hounds have been kept at bay... My heater is out because I am tearing the car down for a proper restoration...

OK, now that I have cleared my good name, on to your question. :grin:

I guess I should ask: Using a factory block mounted mechanical pump, do I need a return line? I plan on using a holley 750 and edelbrock 383 manifold. I figured that a stock fuel pump was matched to that holley carb and I would not need a fuel regulator OR a fuel return line.

Is that an incorrect assumption?

Correct Assumption. With a standard Holley 750 (without the vapor return), you can just use a standard canister that only connects the valve cover to the air cleaner. There is no connection to the carb or to the return line. The entire return line can be removed if you wish. This is the way the non-California cars were plumbed.

Hawk

 

[short stack]

OK, now that I have cleared my good name, on to your question. :grin:


Hawk

LOL!! Glad you can take a little friendly ball bustin Hawk! All in good fun my brother. So, I rechecked my lines, and my "return" line that is bolted to the passenger side inner fender and then goes down along the frame back to the fuel tank is capped with a rubber cap. I dont know where this car has been for the last 40 years, but it KINDA LOOKS like it could have been that way for a long time - maybe factory??


So, if I do get the fuel tank with the 4 nipples for going to the vapor cannister and I hook up all those lines, no gas leaks? No gassy smell? I dont like gas in my rear end, and my wife doesnt either. ANY potential problems with the "cannister" in the trunk? Looks like that is a total sealed system.

Lastly - where do you guys recommend buying a new fuel tank?
thanks Hawk

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[HawkRod]

SS,

The return line is made up of two metal lines connected by hoses. The first hose is from the breather to the line on the fender. Then just behind the front wheel (under the car), there is a small rubber connector to the long line that goes to the back of the car, where again it ends in a rubber line that travels to the canister.

Will you have gas smell? No more than if you had a leak in your supply line. I have mine hooked up and drove the car maybe 200 miles before I started the restoration tear down. I never had any gas smell. With fresh hoses and hose clamps, you shouldn't have any problems. Perhaps others can speak to any issues with this system, but I don't think there are. Many emissions systems get such a bad rap just because of the name, but this does nothing to harm performance.

One though is that if you get rid of this system, you may have to change to a vented gas cap - not sure of that though...

As far as where to buy - I just bought mine from Rock Auto - Spectra tank. It fit perfectly and I had no issues whatsoever with replacing it. Quick and easy...

Finally, your wife's likes and dislikes are not my concern, but she sounds like an intelligent woman... (smile)

 

[SlinktRR]

The car has a 383 engine and I see photos of some additional fuel / smog cannister on the passenger side down by the fuel pump? Is this necessary? Im thinking I just use a tank without all the vapor stuff and run a fuel line straight to the stock mechnical fuel pump and then direct to the holley 750. I dont see a need to run a return line to the fuel pump.

Are you talking about the vapor separator canister (black filter canister with 3 hose barbs)? OEM setup was to have the canister at the fuel pump oriented with one barb up (fuel line to carb) and 2 barbs down (middle barb hooked to fuel pump outlet, other barb hooked to return line). This is useful to have to prevent vapor lock on hot days and while not necessary it's worth having IMO.

The service manual says it was only on 440's or 426 CID applications for 1970, but if you have a return line it may be worth using it with the vapor separator if its not a by-the-numbers restoration.

 

[HawkRod]

See CAS Evaporative system from service manual. This is what I was describing. Crappy screen print, but hopefully you get the idea.

I am not sure about the other system described by SlinkRR. I did not find that on my 383 car but that doesn't mean anything. I'll see if I can find any info on it and if it was also used with the system below...



- - - Updated - - -

As described by SlinktRR, there is a fuel separator. I found it in the manual but it over two pages and a PITA to copy and paste. It does describe its use for 440 and 426 engines, and hooked up as SlinktRR describes. I found nothing to describe how it returned to the tank. Did it Y together with the CAS system return? I don't know and did not see that described. Perhaps someone else knows...

 

[SlinktRR]

No the CAS system is separate. There was a vapor return line that was run along with the fuel line from the tank (both steel). This was connected to the vapor separator. Only purpose was to prevent vapor lock, not emissions control.

My car is a 383 air grabber car but at some point years ago a 440 was swapped in with a return line and separator. I put a fresh 383 in to replace the 440 but still use the vapor canister and vapor return. I don't have the CAS breather or return.

 

[HawkRod]

No the CAS system is separate. There was a vapor return line that was run along with the fuel line from the tank (both steel). This was connected to the vapor separator. Only purpose was to prevent vapor lock, not emissions control.

My car is a 383 air grabber car but at some point years ago a 440 was swapped in with a return line and separator. I put a fresh 383 in to replace the 440 but still use the vapor canister and vapor return. I don't have the CAS breather or return.

I guess what I am confused about is that the CAS has a line that runs with the fuel line as the return too. So my questions are:
1) Were there cars built with BOTH the CAS and separator (e.g. CA car with a 440)?

2) If yes to question #1, were there TWO return lines? I doesn't make sense to me that Plymouth would run two separate lines back from the firewall to the fuel tank, since both were intended to feed vapors back to the gas tank. If there were cars with both systems, were they connected together somewhere in the engine compartment to ONE return line?

 

[SlinktRR]

I cant answer these questions as I'm not a restoration expert. However I talked with a man at Carlisle this year who had a professionally restored California spec 383 1970 RR. Very, very nice car. I took a few pictures since I had never seen anything like it in the flesh. Hopefully it helps a bit.

The key difference as I see it is that the CAS goes through the fender and the vapor return line from tank to separator runs underneath. You can see this car has the breather for CAS. The other pictures show the location of the emissions tube in the trunk and the routing of the lines to the tank.

 

[HawkRod]

Thanks for sharing. I remember drooling over (on) that car myself!

The CAS system has a steel line that runs down the fender and it connects to the hard line that runs from the (approximate) bottom of the firewall back. These two lines are connected via a small piece of fuel line. I wonder if this connection was there so the three lines could all be connected together? That makes the most sense to me, but that is only a guess...