'71 440 HP VAPOR SEPARATOR experts please!

Hi everyone.

I have 1971 C body with the original 440 HP motor and original Carter AVS 4968S carb. It uses the fuel vapor separator between the fuel pump and carb.

My questions are: Does this also filter the fuel? And if not, then did the factory use a filter between the line at the frame and the pump?

Thank you to everyone in advance for your reply.

God Bless Our Vets.

It's a fuel separator not a filter, the sock in the gas tank is the filter.

That's my understanding too from what I read in the 1971 parts catalog and chassis manual. I am replacing the fuel sender, sock, four rubber hoses and ground strap.

However, many have encouraged me to put a universal 5/16" filter between the tank and pump. I guess as an extra ounce of prevention to protect a restored carburetor.

Does anyone else do this?

Why did they not use a filter on the B/RB cars when they did on the small V-8 & slant six cars?

383/400 cars did use a filter between the pump, and carb. The vapor separator does have a screen inside, but no repo on the market has said screen, and on the nipple for the return line there was a .060 orifice which the repos also don't have. From what I gather Frank Baldason is the only person that has them with a screen.

WoW!

Thank you for your reply 71birdJ68.

I put a filter in my system right before the pump. The separator I bought may have the wrong size hole so I need to pull it off and look. I’ve got an NOS one for my bird when that one gets ready to fire.

Trust me, all repo separators have no orifice. What you can do is take a bolt the same size as the hose that goes from the separator to the hard line and drill the .060 hole in it, cut the head off, and put it inside the hose.

Okay...

So I bought a reproduction vapor separator off ebay. The nipple on it that goes to the vent hose appears to be the correct size. It has a very tiny opening as well. I have not measures it yet.

Do I need to worry about the orifice???

The bolt as a restrictor is a good idea but I would kick it up a notch & use a drilled allen set screw.

The opening of the nipple to the vapor return line on my reproduction separator is 1/16".

Is this OK?

On ebay JS Brown or 521 Restorations sells the one that will work. His listing has a diagram of the separator. There are ones being sold that the vapor return size hole is to large and this allows gas to run back to the tank instead of vapor. I do know people that block the tube off which does eliminate the issue on the bad ones.

I don't know if the 71 style is the same as the 69 or not but I put one on my roadrunner and I ended up soldering up the return line fitting and then hand drilled the fitting back open to the correct opening size.

Well 1/16 is .0625 so it should work fine as the factory hole was about .060. Ron

I thought Franks had the screen, and the correct hole? I bought one from him for my 69 440 thinking it was, its already installed. I broke the cam in on a run stand, so I wouldn't have seen any problems from the hole being too large yet.

Duane

Thank you every body for your input.

I guess I will know if there is a problem after I run the motor. The tattle tale I assume will be raw fuel exiting the vapor return nipple.

Were these ever available in the auto parts stores or were they just dealer only???

The problem can be that it might mess with the fuel pressure if the hole is too big.

They are suppose to be a return line, the system is suppose to work so that if you return fuel from a .060 line, it wont stay stagnant,heat up and vapor lock. when the extra supply is needed at the carb, it is easier to travel thru a 3/8 line than a .060, once the needle closes or cycles, it becomes a return line again. same as a modern fuel system. if the hole is too big, it will starve the carb.

Duane

That is the problem with the hole being too large on the vapor return nipple. The car will run down road just fine for a little while and then it will starve for fuel as more is being diverted back to the tank than going to the carb.

That makes perfect sense!

Does anyone know if these were once available at you local auto parts store???

I bought some from rock auto and the return line hole is too big. I was going to modify them and make the hole to match my NOS one. I use a filter before the pump anyway. They were cheap. I bought one from year one and installed it before I checked the hole. I bet it is too big as well.

Lol
I installed a 035 mig welder tip in the return hose after
connection - it fit snug in the rubber return line
Havent lost fuel pressure Or vapor locked in a while.

(Put a three outlet fuel 'filter' in there and fuggitaboutit...

Been running one for many moons...

Zero issues...

After reading this post I decided to check mine as I've always had issues starting the car after sitting after a period of time. I actually had to put fuel directly into the fuel bowl for it to start. Heres the pic of the return line, full hole, maybe this is my issue. When I disconnected the hose it was full of fuel.

Sorry to Hijack, but I have a related question. I'm running a 440 six pack that does suffer from vapor lock issues. I have an electric blue Holley pump regulated to 6psi.

I was thinking about using the stock fuel line as my return. Since I'm not running a mechanical pump at all, will adding the vapor separator (with .060" hole) help me???

There should be zero fuel in the return line. The other issue that I believe is with the fuel separator that you have is that the tube length in the unit is to short. Either way I would replace it.

I ordered a new one from Frank B.. I'm going to open this old one up and look inside when I remove it from the car.

Good idea opening it up. Do send pics of it.

There were many bogus separators in the marketplace. Besides the return line having no orifice, there was no screen inside and the tubes were the incorrect length!!!! This is one I bought for my 6bbl - junk. Your return tube looks like mine - with no orifice, so I suspect it is a bogus one.
Jim

I opened mine up today, the orifice is wrong but the tubes inside appear to be the correct lenght and has a screen.

I’m not an expert but I have my oem one from my Superbird that I have measured and compared to two ones that I have bought. The first was from Year One and had the big (.115 ) hole in the return line. Using a wire with a hook on it, I determined that all three units had the exact same length tubes as my oem. The other unit I bought had the proper size hole as the oem one did. It was not made as clean but it was .060. I’m not sure if it has the screen or not. I bought three of them and just used one on my Charger to replace the new and wrong Year One piece. I’ll see if I can find where I bought these three from. I’ll try and post a picture as well.

This new phone will not let me see the attachment but the oem is on the left, the small hole is in the middle and the big hole YO unit is on the right.

You may find that even the .060" hole can be too big. I discovered on my engine that the larger hole allowed a 2+ psi drop on the fuel pressure measured at the carbs. I soldered the hole closed and drilled it out to .030". My pressure loss was now less than 1 psi and still large enough to pass any vapor and fuel back to the tank. Zero issues even in 95+ degree heat.

I agree- 0.060" is too large. I soldered mine and drilled with a 0.040" drill.

Do you need that return line at all. Isn't that part considered a polution control device. What would happen if you blocked it all together.

It's there to prevent vapor lock, but also, if you plugged it up, it could cause the fuel pressure to get to high.

what about the cars that only have a fuel filter, how do they get away with no return line. I guess it must be vented somewhere then?

they vent from boilin over and floodin your engine when it sits on a hot shut down .

i was very sucesful with the mig welder tip ..

I disagree

Yeah E that's not right. It's a fuel return line.

I disagree [/quote]

Yeah E that's not right. It's a fuel return line. [/quote]
It's actually a vapor return line. Fuel can run through the line but if there's fuel in it something is likely wrong like a blocked fuel line or clogged separator.

Yeah E that's not right. It's a fuel return line. [/quote]
It's actually a vapor return line. Fuel can run through the line but if there's fuel in it something is likely wrong like a blocked fuel line or clogged separator. [/quote]

You are both right! If vapour accumulates in the top of the separator, then it will flow into the return line. If there is no vapour, the fuel will flow into the return line and the flow is restricted by the orifice. I bought a repro for my 440-6 bbl and could not get the engine to start. Found out it was a knockoff and there was no orifice in the return line. All the fuel was going straight back to the tank!!

go to 12.24

https://www.youtube.com/watch?v=P6eY0DOO7LY

That was a neat video. Enjoyed that.
Well mine had no orifice so I installed a new reproduction. In a month or so I will see if it made a difference. Mine was also very hard to start.

https://board.moparts.org/ubbthreads/ubbthreads.php/topics/2443699/3.html

this is good info!!

I just ordered one from 521 Restorations. He says his are the right ones.