BUILD THREAD “The Juggernaut”

[Kiko]

I want to say someone here did that. They ran the vent to behind the filler neck when you drop the license plate you could see it back there. Optionally, you could mount it way up in the top area in front of the tank, which would alleviate any issue of potential acceleration problems with the vent in the back.

Fuel Tank Vent Update 11/22

Im planning on starting my 81 this coming week. FINALLY !! Ive got a couple of things left to do. One of them is to put gas in the tank. Back in August I started a thread about the tank vent. Only had a single reply. I searched the threads last night and I figured I would just buy one of these...

gbodyforum.com

This topic has been very interesting to follow. I'm in the process of changing fuel tanks and this is very timely! BTW, I've found two pics of the vent behind the filler neck, which is what my plans are.

 

[64nailhead]

Great. Now I've got that to look forward to.... lol 😆

Not much leaks if the cap is fully seated, just gets moist. Unless it isn’t fully seated, then that’s a different story. But it evaporates fast, just don’t be tossing cig butts out the window 😉

 

[Rktpwrd]

I was rooting around in the garage looking for a stock fuel tank sending unit that I thought I had, when I came across the Howe Racing Enterprises bumpsteer correction center link I ordered several months back. I had tucked it away as I had other more pressing priorities on the go at the time, and promptly forgot all about it.

Figured what the hell, it should only take a few minutes to pop on, and just like that, SQUIRREL! I got distracted. Well after removing the new stock replacement Moog center link and placing the two side by side, WOW, what an eye opener! The Howe unit is so seriously beefy and robust compared to the puny stock one, it isn’t even funny.

Obviously the heights at the idler and pitman arms are adjustable due to the custom shimmable pivots, but also note the lack of “kickup” at the ends, along with the gussetting on the Howe piece:

Anybody notice the difference in diameter? The stock link measures in at a paltry 27/32nds…

…while the Howe piece blows that away at a SOLID 1”!!

I’ve just got the Howe link installed hand tight for now, but so far no clearance or interference issues.

I may still have to notch the middle frame horn where the jounce bars attach if the link needs to be adjusted all the way down, but so far it’s looking good.

VERY impressed with this bumpsteer correction link!

 

[Supercharged111]

Strange that they gusseted that one little bit?

 

[Rktpwrd]

Strange that they gusseted that one little bit?

It’s at the pitman arm/steering box end, so maybe that has some bearing on it? I would guess there’s a definite reason for it, or else they wouldn’t have bothered. Probably something that was revealed in testing.

 

[Rktpwrd]

Found it!!

Hmmm, this looks suspiciously like a vent to me…

Think what I’m going to end up doing is routing this “vent” tube via another hose alongside the Holley rollover vent I’ve got coming, and that way it can vent both ways: out through the rollover when tank pressure increases, and into the tank when tank pressure decreases (vacuum from fuel being used). Probably put a small K&N filter breather on it like I did on Olds Cool, but much cleaner and more professional.

 

[Supercharged111]

It’s at the pitman arm/steering box end, so maybe that has some bearing on it? I would guess there’s a definite reason for it, or else they wouldn’t have bothered. Probably something that was revealed in testing.

I would like to think there's good reasoning, but it would seem to me the longer run to the idler arm would have more flex? Plus it's already beefed up to begin with. Without knowing, the logic doesn't seem obvious, but with or without it's clearly an upgrade in every way. How do you plan to approach your bump steer? You can burn up some hours with that.

 

[Rktpwrd]

How do you plan to approach your bump steer? You can burn up some hours with that.

Same way I always do, with lots of reading and research. I’ll have to figure out what guys are using as a baseline first, then make my adjustments from there. I know full well it’ll take some time, I’m anticipating lots of trial and error based mostly on how the car reacts to the changes. I imagine you have some experience with this in your racing, I’m open to any suggestions and advice you might have.

It’s moot at this point anyways, as I’m still a long ways from completing the car.

 

[Supercharged111]

I'm ashamed to concede I have no personal experience with correcting bump steer. That said, you need to determine your range of travel and optimize the toe curve for that. You do so by sweeping the suspension through an assumed range of travel with the springs removed with a laser pointer aimed at something far away to measure the change in toe through the range of motion. You then alter the shim stack and observe whether the swing in toe increases or decreases through your range of suspension travel. You should settle on what appears to be the least bit of compromise.

 

[69hurstolds]

Your original sending unit "vent" is a vent, as you stated. On G-bodies with gas, there's only TWO types of sending units. A two-port and three-port. The two-port has a charcoal canister vent and a fuel supply to the pump. In the three-port, they added a return-line from the pump. Depending on which type of fuel pump was used, that determined which sending unit you got. And that seemed to change year over year. I really don't know what the criteria was. Oldsmobile V8s used the three-port a lot. Chevies, not so much. The part numbers are only 1 different than each other as well. 25001612, the two-port, is what you have and 25001613 is the three-port. The last number just happens to coincide with the number of ports for A/G47. Wagons are similar, but obviously different part numbers (25000757 for 2 port and 25000758 for 3 port).

There is an actual RPO for the fuel line return. It's K15. Although, I do not know what triggers it. ALL 307 VIN 9's use it because ALL 307 VIN 9 engines came with the same type of fuel pump which has a return line.

Looking at john87442 crusty 442 frame below, you can see the vent, return, and supply. All G-bodies should have at least the vent and supply. The "heat shield" plate below the supply/return lines in the pic is only found on VIN 9 cars with the dual exhaust. Single exhaust cars didn't get those.

This portion below shows where the lines route to on the forward part of the frame. Where the canister is on the passenger side. When the canister is on the driver side, you should see the vent line run right up the driver frame rail in front.