thanks five7kid ill try searchingfor these, does anyone know the part numbers of these fittings or have other ideas?

 

RUS-640850 3/8"
RUS-640860 5/16"

Both use AN-6 fittings

 

Since this is a discussion about the gas tanks and fitting them into our 3rd gens....Has anyone ever tried the reverse of the "mod the sender" method. Specifically, can our 3rd gen gauges be modified to interpret the 4th gen signal? I believe it was 0-90 Ohm vs 90-210 Ohm?

Edit: I ask because I have a spare fuel gauge I could tinker with if it's a possibility. Easier to mess with the gauge than the gas tank in the garage at the apartment lol. Neighbors hate me as it is.

 

Honestly it is as easy as getting the proper resistor board. I think it took me all of 5 minutes to swap the board into the tank since I already had it out. With enough time you can make almost anything work but I doubt anyoine has bothered. If you have a 4th gen cluster you may be able to adapt the gauge to work in the 3rd gen cluster but depending on the sweep from the factory in the 4th gen cluster it may not be an accurate reading anymore

 

where exactly do you cut the filler nect to install it in a 3rd gen?

 

That has been covered several times

 

I know but i want a for sure answer because Im not trying to mess it up

 

Use the 4th gen filler neck. Trim the rubber connecting hose as required to get it to line up properly in the filler door.

 

thats what i thought. i was more so looking for an exact length

 

I believe the number I heard was 1-1/2" (been awhile). I don't remember details, but I do recall mocking it up, seeing how the hard parts lined up to each other, then trimming the rubber accordingly.

 

seems easy enough, thanks

 

Can the tanks be used on carbed engines or only fuel injected?

 

Sure. What were you thinking of doing for the fuel pump?

 

i have yet to get one and take apart my 85 for restoration, i was just thinking it would save weight and mines all rusted out so maybe if i either rebuilt the stock one or bought an aftermarket, because im positive the 4th gen one wont work

 

You can use the 4th gen pump. You'll have to gut the pressure regulator built into the tank's pick-up/pump assembly return port (basically a check valve), and use a return-style regulator like a Mallory 4309.

Oh, I have a stock carb tank that's in good shape as well. It's a big part to ship, but can be done.

 

Stick a TBI pump in the LS1 sender so the pressure is more inline with what youll need

 

I'd stick with the LS1 pump. The reg will handle it just fine. If the pump eventually fails, you can put in a lesser pump if you like.

 

How would you attach those fittings from Russle to a compression fitting so that you could attach it to hard line?

 

You are going to need a short amount of hose in between the tank and the hard lines on the car, you can make the swaps there

 

I didn't use any hose. I put the Russel fittings on the tank, then bent and flared tubing over the side of the tank. I used compression fittings from there to attach to the lines going to the filter.

 

ok...i know this post is old and it answered most of my questions but.....i have the assembly ready to go back in my car and plan on getting the autometer 0-280 ohm gauge to get the tank to read right. Would that work? Also i plan on running an external fuel pump with a regulator on it b/c the car will be duel 4 barrel carbs on it so i plan on leaveing the old pump in the set up just not hook it up and use the pump as like an extention to allow the fuel to flow through it with out actually hooking it up. However i'm not to that part yet so i'm not sure if it going to have return lines or not. Canyone more familure with carbs tell me? If any of thie set-up sounds weird plz let me know. It all works in my head.

 

sry forgot to mention the engine going in it is a 396 with an 871. That is why duel 4 barrels.

 

Question: if one were to get the tank with ALL the lines right to the fuel rail, this would make it a plug n play swap correct??

 

The lines arent the problem. LS1 tank swap con's are tied into its ability to send the propper signal to the gas gauge.

 

No. The 4th gen lines are routed differently and because the front k member and suspension are so different as well its highly impractical to try and use them. The lines that come from the tank to the fuel filter are useful however. Besides after the filter its easy with LS1's anyways as they dead head at the rail ( no return ) so its only one line you have to run or re-use off your third gen.

 

right, i read that on another thread and saw the ohm resistors swap in the gauge to correct it, i just thought with the lines complete it will save me time, $$$ and a headache. (edit, quote was for previous post to this one) so cant i just bend the 4th gen lines to work right?

 

The lines coming off of the 4th gen tank are plastic with plastic connectors.

I used a 4th gen tank and pick-up for the LS1/T56 swap. I got Russel disconnects with male AN fittings and fabricated all new aluminum line. Here's a pic that shows the basics:




Aluminum line is pretty easy to work. Much easier than trying to re-do factory line (I reworked the factory 3rd gen line for the LS1/4L60E swap - it was a lot more work).

 

I see what you mean but i read on another thread that a member used the 4th gen tank and full lines all the way to the engine and only had to modify the lines near the front since they came out into the middle of the car alittle, i just got a tank complete with all lines and the lines that run all the way to the Fuel rail so i was thinking i can just bend the line to where it needs to be, change the sending unit and it should be plug n play once all installed.

 

Maybe a dumb question...but is the V6 00-02 tank the same as a Ls1 equipped vehicle? Or similar

 

Similar

V6's used a return style fuel system, so it wont have a built in regulator. Use the common C5 filter/reg unit and youll be set. Youd still have to do all the other changes like sender, fittings, filler neck etc

 

If anyone needs a plastic tank I have one for sale. PM me if needed.

 

Why does the pressure line have a "T" past the filter? what was that line used for in the original LS1 setup?

 

The tee is before the filter and it is the return line for the system. The fuel pressure regulator is in the tank at the end of the return line

 

I have the "T" after the filter so the fuel going back to the tank has been filtered. It'll work either way, but that was the way I preferred.

In case that detail was missed, the 4th gen V8 tank pick-up has a relief valve in the return line to control system pressure. So, it doesn't really matter where the "T" is. You could build it into the lines up on the tank if you wanted. Or up at the engine.

 

Oh, the return just opens the pressure line into the tank right there, Instead of going all the way to the rail and back like a tpi system.

 

I understand the '98 f-bodies had the return line up on the fuel rail, but '99-on they used a system similar to what I built.

Vettes were different. Had the return and pressure reg built into the filter.

Oh, the main reason I put the "T" after the filter is to protect the return check valve from debris.

 

Is there any hope in using the factory Metal tank and pump from my 98 doner car or more hassle than its worth? Obviously It would be difficult to shorten the filler tube and the charchol can is seperate. Any Suggestions?

 

IMO find a 99-02 plastic or use the stock metal thirdgen tank...unless you need a charcoal setup

 

I have a 98 LS1/T56, I also have a plastic tank.
At the time that I got the tank I didn't think evap would be any different between 98-02. I am trying to do a smog legal swap.

Is there a way to make the 98 style EVAP work with the plastic 99-02 tank?
OR
Is there a way to make the 98 style EVAP work with the stock 89 RS tank?

 

Theres always a "way" but its not always easy. The EVAP system takes info from a lot of sources including the factory fuel gauge which by now Im sure you know is a different ohm sweep than the third gen gauge. So you would at minimum have to swap to a fourth gen fuel gauge and possibly the entire dash and dash harness if you couldnt isolate the gauge to a satisfactory aesthetic and figure out how to extract the relevant wiring.

Good luck

 

i cant find a diagram for the wiring on the tank, i put mine in Sat and if remember correctly theres 4 wires off the tank pump/sender connector and only 3 wires on my 3rd gen in car harness, anyone know what im splicing? (yeah im really That bad at wiring, it would help if i had a shop manual XD)

 

"pinouts" https://www.thirdgen.org/forums/ltx-...ear-brake.html

post #4

 

I recently bought a used 2001 V8 tank from a junk yard. Everything seems in good condition. I'm in the middle of modifying the bucket for twin pumps and the proper ohm reading. Anyway I was wondering if I should clean the tank out while I have it apart? I doesn't seem dirty, but you never know. What would you use to clean it, since it's plastic?

Thanks.

 

This has been most helpful.

 

i didnt think id have to post again but im alittle confused about the tank and factory lines im working with. in the pictures posted in the thread, theres one feed going to the fuel filter and one line T'ing into that which was said to be the retun line, on mine (from a 99 LS1 car) it has a third flex to hard line that connects to a hard line and runs up the engine bay next to feed... is that another return line?? maybe i maissed something....looks like i have 3 hard lines where one T's off to the feed and another long line from tank to engine....????? i can take a pic and post if needed

 

Evap is the 3rd connection

 

thanks, i was just about to post back too, ive been working on my swap for too many consecutive hours... frying my brain

 

"Restoring" my 87 IROC, have plans to eventually put in an LS1, my fuel pump is dead, so I figured I'd just buy the newer tank to save some money in the future. But will the 4th gen tank work with the 5.0 stock engine?

 

Yes, the 4th gen tank will work with the 5.0. LS1's typically use higher fuel pressure, so the pump in the 4th gen tank will have a higher output, however your regulator on the 5.0 should take care of it. The only other issue I see would be the vent and return lines that your IROC uses. The 4th gen tank has an self contained charcoal canister and I dont think it has a return line. If your in an area where emissions testing is important these might be things to consider as well.

 

I'm looking to do the same thing .... using a plastic tank on my 3rd gen 5.0. Anyone done this before and is there any documentation on matching up the wiring?