Fuel line questions

[bull]

1. The 383 Chargers did not come equipped with fuel vapor separators or return lines as this was a high performance addition to cars equipped with 440 and 426 engines. My question is do you think it's a good idea to use these setups on 383 cars too? Do they make a big difference in preventing vapor locks?

2. I got a bunch of s-clamps in a fuel line hardware kit from megaparts. Are these used for attaching the return line to the main fuel line? BTW, I called megaparts with this question but the woman I talked to didn't know. She did tell me the kit I got from them was the last one they had in stock at the time so it was a bit of a mish-mash collection of leftovers.

3. Is there more than one p-clamp used on the main fuel line besides the one that gets bolted to the shock mount cross member? The megaparts kit I got also contained three p-clamps and two p-clamp mounting bolts (one extra p-clamp was provided accidentally). I'm assuming that the kit is a catch-all designed for use on R/T and non-R/T Chargers so my guess is that the second p-clamp is for the return line, no?

4. How can you tell if you've got a decent sending unit? When I first bought my 68 my plans were to make her a driver so I bought a fuel tank and a Spectra Premium Industries sending unit off Ebay and it's been sitting in its box ever since.

[Dans 68]

O.K., I'll bite on question 4.    Most likely you will need to calibrate the fuel sender no matter what brand you buy. I believe the originals were non-linear (semi-logarithmic)(to better follow the resistance values versus float arm angle) while the aftermarket ones are linear; I've attached a sketch to illustrate what a non-linear versus linear sender will read. The resistance range on the sender is typically from around 8 ohms (full tank) to 80 ohms (empty tank)(I used 73 ohms as that was my empty tank installed reading, with 23 ohms being half the float arm range), typically. (http://www.dodgecharger.com/forum/index.php/topic,68992.0.html) You will need to see what resistance your sender exhibits when it is installed in the tank as the float arm typically cannot move its full range in the tank. The gas gauge will need to be fine tuned once you know the resistances (I used a resistance board and 5 volt power supply with the gas gauge removed, and adjusted the full and empty set points to my liking). Do a search on "fuel sender unit" to find lots of threads. I personally would precisely set the full mark and empty mark and not worry about the mid-point fuel mark...it is more important to me to know when I really need fuel than when I'm half empty.  

Dan

[Just 6T9 CHGR]

1)...cant tell ya if the vapor separator really helps that much but I believe the 440/Hemi engines used a higher volume fuel pump which utilizes the return line (dont quote me on that )

2)S shaped clamps do tie the return line to main line

3).....hmmmm  Off hand I can only think of the one on the shock mount on my R/T

4)....what Dan said

[maxwellwedge]

Bull - Here are some pics....

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more...

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Mo - Mo...

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Mo Mo Mo

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God, make it stop!

[Charger-Bodie]

I think the second p clamp is for a car with torque boxes.

[elacruze]

1. The 383 Chargers did not come equipped with fuel vapor separators or return lines as this was a high performance addition to cars equipped with 440 and 426 engines. My question is do you think it's a good idea to use these setups on 383 cars too? Do they make a big difference in preventing vapor locks?

2. I got a bunch of s-clamps in a fuel line hardware kit from megaparts. Are these used for attaching the return line to the main fuel line? BTW, I called megaparts with this question but the woman I talked to didn't know. She did tell me the kit I got from them was the last one they had in stock at the time so it was a bit of a mish-mash collection of leftovers.

3. Is there more than one p-clamp used on the main fuel line besides the one that gets bolted to the shock mount cross member? The megaparts kit I got also contained three p-clamps and two p-clamp mounting bolts (one extra p-clamp was provided accidentally). I'm assuming that the kit is a catch-all designed for use on R/T and non-R/T Chargers so my guess is that the second p-clamp is for the return line, no?

4. How can you tell if you've got a decent sending unit? When I first bought my 68 my plans were to make her a driver so I bought a fuel tank and a Spectra Premium Industries sending unit off Ebay and it's been sitting in its box ever since.

1. Vapor return doesn't affect vapor lock; it reduces the amount of air passed into the carburetor due to slosh (expected to be worse in HP cars of course) which stabilizes float level and fuel aeration
2. Nice photos!
3. Dunno...
4. My sending unit (circa 2001) was way off, I just bent the float arm so that it read correctly at empty. I got lucky, and it reads correctly at full also. 

[bull]

Wow! Awesome reference pics. I didn't see a second p-clamp so as Brian said I guess there's only one.

1. Vapor return doesn't affect vapor lock; it reduces the amount of air passed into the carburetor due to slosh

Really? I thought the problem this thing solved was premature vaporization of the fuel prior to it entering the carb.

[elacruze]

Wow! Awesome reference pics. I didn't see a second p-clamp so as Brian said I guess there's only one.

1. Vapor return doesn't affect vapor lock; it reduces the amount of air passed into the carburetor due to slosh

Really? I thought the problem this thing solved was premature vaporization of the fuel prior to it entering the carb.

Only if the vaporization happens before the return line. Once it leaves the pump and heads up the block, there is no return to tank, so if it boils there it's all the same. I don't suppose that the fuel line at the frame gets significantly hotter on a 440 than on a 318 once up to temperature.

[bull]

That makes sense.

After thinking about it I don't really see the need to run a vapor separator. The only experience I have to compare things to is the '70 Charger with a 383/auto I had growing up. It didn't have one of these and it never vapor locked. It also didn't have frame connectors, torque boxes, disc brakes, seat belts, electronic ignition, rear sway bar (maybe not even a front), etc., and yet I drove that thing like I stole it almost every day for 11 years. Rarely did it miss a beat. It was probably the best running, most dependable and toughest car I've ever owned.

[bull]

You will need to see what resistance your sender exhibits when it is installed in the tank as the float arm typically cannot move its full range in the tank.

Ok, how do you calibrate the unit? And how do you move the arm up and down when inside the tank... of do you?

[Dans 68]

I actually emptied the tank (don't ask...  ), measured the empty resistance from the sender unit, and then filled it back up, one gallon at a time, and measured the resistance after each addition (yes, I'm anal). Um, be sure the car is on a level surface.     Be sure to give the sender unit/tank a few light whacks after each fuel addition to ensure the swing arm does not hang up for any reason and is where it should be. A running car will ensure the float arm get's the necessary vibs and centers itself. Once you have the resistances you can adjust the gas gauge (out of the car) to the full and empty set points using a resistance box and 5 volt power supply.

Or you can just throw it in and wing it.    (knowing you and your efforts to date on your baby this is not going to happen  )

Dan

[bull]

It's going to have to wait until later 'cause I'm not in a position to do that yet. Sounds like one of those fine tuning, working-out-the-bugs projects to come once it's all put together. 

[bull]

Just thought of another question while looking at fuel sending units. Do all 3/8" sending units have the built-in 1/4" vapor separator tube (two lines)? It seems that's what I'm seeing so far. That and all the 5/16" units do not have the vapor tube (one line).


Also, not sure how much of a problem this will be but I bought a 3/8 fuel line before realizing I got a 5/16 sending unit six years ago when I was planning to make the car a driver. Ooops. Will I be able to connect a 3/8 line to a 5/16 sending unit? Maybe a better question is, should I? At the other end I can theoretically install a 3/8 pipe to the fuel pump inlet and then go back to a 5/16 pipe on the outlet. Basically I'd like to avoid the hassle of sending the 3/8 line back in exchange for a 5/16 if possible. But if I have to, I have to.

[Dans 68]

From a purely functional perspective I don't think it matters. It's not as though the fuel pump will be"sucking" so hard on the 3/8" fuel line that you will start cavitating the gas as it leaves the 5/16" sending unit and enters the 3/8" fuel line. It should work just fine. 

Dan

[bull]

Yea, my biggest concern is getting a good seal on the 5/16 fitting with a 3/8 hose or getting a 5/16 fuel hose over the end of the 3/8 line. I suppose it would be better to try getting a 5/16 hose on the 3/8 line.