Hi guys, I took comparison pictures of the 3rd and 4th gen gas tanks and gas lines for those who are interested, since I haven't seen any comparisons or pictures of 3rd/4th gen tanks and lines. The thirdgen stuff is from an '85 305 TPI and the 4th gen stuff is from an '02 LS1. The LS1 lines would fit except for the bend in the middle, which can probably be taken out with a brake line bender. However, that would mean an extra foot of line in the engine comparment and so you'd have to chop the ends off and reweld them, or bend the line into several coils to take up the extra slack. But you'd have the quick-connect fittings. I'm also curious how those of you who have done the LS1 tank swap managed to route the three 4th gen lines coming out of the tank to fit the 3rd gen lines (4th gen uses 3-into-2 lines, 3rd gen uses 3 lines). The thirdgen lines are pressure, return and charcoal canister, but the 4th gen are pressure, return, and something else, as there are two lines that connect to the pressure line... before and after the fuel filter. Please note that the 4th gen lines still have two small brake lines running front to back. I didn't feel like taking them off for the pictures. For the mods: I would host these pictures myself, but I don't have reliable hosting and I'd like these pictures to be here if someone needs them later on down the road. Notes: (last updated 8/11/05) Parts: Pure Choice Motorsports #5800, both adapters for the 3rd gen lines up front. $34.95. Pure Choice Motorsports #5810, same as above, but for the returnless LS1 fuel system. $20.95. For the rear connections, I'll use part of the 4th gen rear fuel line (filter part) and connect it to the 3rd gen line, so that solves the pressure and emissions connections. For the return line, I'll probably use a quick-connect to hose fitting (if there's such a thing) and attach it to the thirdgen's smaller line with a piece of hose and 4 clamps (two at each end to make sure it stays on). If you ever need to take the fuel fittings off, it's easier with a quick-disconnect tool, like this one from CTA Tools (part #A378, $2.57). Some interesting fuel-related links regarding thirdgen/LT1/LS1 fuel systems -"Modifying the LT1's fuel system for third gen use" -"Braided AN from PUMP TO FUEL RAIL??" I will update this thread with a parts list of what you will need to use a 4th gen tank in a thirdgen as I find out.

3rd gen line.

4th gen line.

Gas tanks.

3rd gen tank.

4th gen tank.

4th gen tank...3rd gen lines


all you have to do is where the filter is take it off and put in the junction from the 4th gen lines.. then cut off the return line and connect that to the smaller line on the 4th gen lines and you have your purge lines...

at the top end of the lines get a couple convertors from the hard lines to -an .. then put one to the rail and one to the purge

i wouldnt try putting 4th gen lines and cutting them up and whatever.. just turn into a mess or gas leakin everywhere


only reason i used the 4th gen tank was cause i used all the wiring... other then that I found it much heavier then the third gen one... a thirdgen one with a better pump would be easier then tryin to get a 4th gen one in there...

I just used the third gen stuff with a Walbro HP 255 pump made it hella easier!

Yes, but to be smog legal you need to have the emissions stuff, which includes the LS1 tank. I've checked out Russell and Earl's but I don't see any adapters for the LS1 type compression fittings to the 3rd gen ones up front (screw on type). Is there such an adapter?

I made my own, I cut the screwed ends off my old fuel lines from the motor, flared the ends and then put them on FI hose I got from AutoZone, then bought the quick connect fittings from O'Rilleys (about 10 a piece) for the other side, then I screwed the ends into the existing rubber lines.

Emissions what that!

the fittings are the metric ones to -6an.. i dont have the numbers but a quick search can findem...

the ls1 you can use ones from street and performance for the quick connect to -an connector and then just a hose between them...

you can also use a cheaper 3/8" compression to -6an and it goes right on the fuel line...

have fun with the A.I.R. and EGR

hey guys,

for those of you that have done this, i have access to a 4th gen gas tank. I am replacing my brake lines to stainless steel right now as well. So i might as well switch to the new tank and make it plastic. my question is, with it being fuel injected on the donar car, and my 3rd gen being carb, does that matter?

am fairly certain my tank has no pump on it, but i havent looked for myself. the only pump is on the motor. Any information would be great

Thanks guys

You can put the 4th gen electric pump on a fuel pressure regulator and then feed that into the carb, but it will involve running some new lines in the engine bay, but probably not much. It would mean getting rid of hte mechanical pump.

Or, and Im not 100 percent sure on this, but I'd bet you could do it, you can remove the carb pickup from your tank and put it into the 4th gen tank, or at least find some way to remove the 4th gen pickup/pump assembly and put the carb pickup in it.

I swapped out the fuel injected v6 on my 87 for a carb 350 with mechanical fuel pump, how should i go about bypassing the electric fuel pump to get an un-restricted flow of fuel? Do they make a replacement pice? Thanks!

Well.. You can cut off the hard plastic line that goes from pump to top.. scrap the bottom half of the module.. Hook up a fuel line to the fitting on top find some way to keep it straight so it stays at the bottom of the tank. I have the top part of the module if you want it. just pay shipping.. let me know