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GS guy
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Joined: December 03, 2007
Posts: 968
Location: Maryland
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 Posted: Mon Aug 31, 2015 3:25 pm Post subject: Flipping a Tank? |
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Anyone ever "flipped" the top relative to the bottom of a VW fuel tank?
I was trial fitting a later model VW tank in my Deserter GT front end and in the standard orientation (front to rear as it would be mounted in a Bug), I'm looking at quite a bit of work underneath to section areas to fit around the R&P steering and relocating the outlet bungs. I figured it wouldn't hurt to try flipping the tank "backwards", and darned if the underside doesn't look like it was made go go in that direction! Low point is right at the outlets and looks like it would clear the steering gear just fine, or at most, very minimal mods - due to the extra underside relief area on the passenger side of the tank. But the top is totally out of whack. Very high at the back and low in the front, and definitely won't fit under the hood that way.
If the top half were reversed relative to the bottom - it would pretty much plug-n-play!
I guess I'd need to take the top off by just cutting inboard of the weld seam on top half only (cut-off wheel)? Flip around and re-weld. Seems like a "lot" of welding, but maybe no more than all the underside mods needed to go the other way - plus little or no extra steel or parts needed!
Don't think I've seen this done before? Anybody even thought about it?
Got a new tank coming and it'll definitely be going under the knife, relocating the outlet and adding a return, internal baffling and adding a new center-hood filler neck. I guess having it opened up like a can opener will give plenty of room to work inside! Any reason to not do this?
Jeff
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BL3Manx
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Joined: August 29, 2006
Posts: 6767
Location: Northern California
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| Posted: Mon Aug 31, 2015 7:40 pm Post subject: |
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They clearance the underside of the tank on the passenger as well as the driver side so the same tank will work for either RHD or LHD.
I'm not clear on what you are gaining by turning it front to rear? |
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joescoolcustoms
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Joined: August 08, 2006
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Location: West By God Virginia
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| Posted: Tue Sep 01, 2015 1:42 am Post subject: |
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No reason not to do it.
I have hacked several, either adding capacity or sectioning out to fit.
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motoRAT
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Joined: May 05, 2013
Posts: 308
Location: Portugal
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| Posted: Tue Sep 01, 2015 4:23 am Post subject: |
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I did
no biggie, just be sure no fumes are in the tank, or it will go bummm
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Dale M.
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Joined: April 12, 2006
Posts: 20379
Location: Just a tiny bit west of Yosemite Valley
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| Posted: Tue Sep 01, 2015 7:58 am Post subject: |
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You do what you have to do.... No matter what, be sure you have outlet bung at lowest portion of tank or you will have a couple of gallons of gas you can not use....
Dale
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BL3Manx
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Joined: August 29, 2006
Posts: 6767
Location: Northern California
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| Posted: Tue Sep 01, 2015 4:11 pm Post subject: |
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| GS guy wrote: |
| I was trial fitting a later model VW tank in my Deserter GT front end and in the standard orientation (front to rear as it would be mounted in a Bug)... I figured it wouldn't hurt to try flipping the tank "backwards" |
GS, I'm a little confused, is the tank in a GS mounted front to rear?
| GS guy wrote: |
| ....the top is totally out of whack. Very high at the back and low in the front, and definitely won't fit under the hood that way. |
Is there less height under the rear of a GS hood than the front?
Looking at the picture of MotoRat's sectioned tank, it can be seen that the clearance for the tie rods is under the forward half of the tank. Does the rack and pinion on your GS not require clearance for the tie rods under the tank in the same area?
MotoRat, It looks like you did what GS described but instead of reversing the bottom, it looks like you reversed the top and I'm assuming left the bottom in the standard orientation.
I'd be concerned with having the fuel quantity sender access hole below fuel level if the tank is full. Its supposed to be fuel tight but there's a difference with "fuel tight" above fuel level and below fuel level. Have you had any fuel fume/smell issues? |
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joescoolcustoms
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Joined: August 08, 2006
Posts: 9054
Location: West By God Virginia
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| Posted: Tue Sep 01, 2015 5:27 pm Post subject: |
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The tank in my Manx has about 3 inches vertical of fuel over the sender. No problems with fuel odors. You should install a new seal on the sender when doing this.
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Bad News Racing 2018 NORRA 1000 3rd in Class
Best Day Ever Racing 2022 NORRA 1000 2nd in Class and first All Female team to complete the race
Everyone is gifted. Some just do not open the package.
Looks like it was painted with a live chicken,polished with a brick and buffed with a pine cone |
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GS guy
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Joined: December 03, 2007
Posts: 968
Location: Maryland
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| Posted: Tue Sep 01, 2015 6:49 pm Post subject: |
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Sorry about the confusion BL3. Here's what I ran into:
The stock VW tank is sort of a "rear sump" design, and for some odd reason the sump is biased towards the driver (left) side. The rear sump helps to clear the steering gear as you commented.
My Deserter is a heavily modified GS tube chassis, and the R&P and tie rods run very low in the chassis, using A arm suspension in the front. The slightly "cab forward" design of the mid-engine chassis means your feet sit a little more forward too vs. a VW chassis seating position. My front firewall/chassis bracing rises from the floor at the front bulkhead - and hits the OEM outlet bung of the tank. To make it fit that way, I'd have to shave that portion off and flatten it to clear the chassis, plus it eats into the upper under-dash room in the cockpit. The top of the tank pretty closely follows the underhood contour (at least the general angle of the top of the tank vs hood). Much more room under-hood further forward and allowing the tank forward ridge to fit underneath.
Also the steering shaft/underside clearance is a little less on the drivers side vs passenger, meaning I'd have to do some sectioning to clear the u-joints and connecting shaft.
Now - when I flip the tank around, the underside slots in like it was made to go that way! Plenty of room in the chassis further forward for the sump (without a front beam or tie rods in the way!), more room under dash in the cockpit and the extra steering gear clearance on the "passenger" side of the tank clears the steering shaft (or very darned close to it).
The top side however, now rises up abruptly in the back towards the dash - like Moto's pic, and the "ridge" along the back of the tank won't clear the underside of the hood in the rear. If I were to reverse the top direction, moving the high ridge back to the front - fitment would be a breeze. Just cutting a new tank apart and welding it back together - a bit of work!
Moto - how did you end up cutting your tank? Did you cut along the flange surface, or where the top starts to rise off the flange? The later tank I'm using isn't symmetrical on top, so a little trickier to do.
Here's a side view of the tank I'm using for mock-up. This shows the "rear-sump" layout of the bottom pretty well.
Just got the new tank in this evening. Looks like a very nice tank! Made in Canada (Spectra brand), and nice heavy gauge metal. Should work great.
Jeff
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Fiatdude
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Joined: April 20, 2009
Posts: 1218
Location: now in MO.
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| Posted: Tue Sep 01, 2015 7:16 pm Post subject: |
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I did a lot of cutting and welding before I bought mine the way I wanted it
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motoRAT
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Joined: May 05, 2013
Posts: 308
Location: Portugal
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| Posted: Wed Sep 02, 2015 10:29 am Post subject: |
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| BL3Manx wrote: |
MotoRat, It looks like you did what GS described but instead of reversing the bottom, it looks like you reversed the top and I'm assuming left the bottom in the standard orientation.
I'd be concerned with having the fuel quantity sender access hole below fuel level if the tank is full. Its supposed to be fuel tight but there's a difference with "fuel tight" above fuel level and below fuel level. Have you had any fuel fume/smell issues? |
yes I've reversed the top, the bottom was in its optimal position but the top hit the fiber on the front portion, so I flip the top and now is spot on, except for the filling neck, STUPIDLY I decided to live it on the OEM position, I should have welded in the middle, I can't fully fill it up or will lose gasoline on left cornering. I haven't had any spillage from the sender unit
| GS guy wrote: |
| Moto - how did you end up cutting your tank? Did you cut along the flange surface, or where the top starts to rise off the flange? |
I've cut along the flange from were the top rises, it's a fairly similar shape when flipped in my type of thank, in your case will be a bit more difficult, your filing neck is on the side not on top like mine
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SBD
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Joined: October 24, 2012
Posts: 3269
Location: SOUTH DAKOTA
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| Posted: Wed Sep 02, 2015 12:24 pm Post subject: |
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| motoRAT wrote: |
| GS guy wrote: |
| Moto - how did you end up cutting your tank? Did you cut along the flange surface, or where the top starts to rise off the flange? |
I've cut along the flange from were the top rises, it's a fairly similar shape when flipped in my type of thank, in your case will be a bit more difficult, your filing neck is on the side not on top like mine |
GS guy, In your case (late model tank) maybe it would be easier to cut around the bottom side of the flange instead of the top side? Looks like the tank is somewhat symmetrical there and might be easier to flip and reattach after cutting.
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| mark tucker wrote: |
| I wouldent waste $ or thyme on building a small motor. build it big so it dosent have to work hard.remember it's only as fast as your foot alows it to be unless you build a small turd then it just stinks as it squishes up through your toes when you step on it. |
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motoRAT
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Location: Portugal
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| Posted: Wed Sep 02, 2015 12:32 pm Post subject: |
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| SBD wrote: |
GS guy, In your case (late model tank) maybe it would be easier to cut around the bottom side of the flange instead of the top side? Looks like the tank is somewhat symmetrical there and might be easier to flip and reattach after cutting. |
nice spotted
I'm with SBD
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GS guy
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| Posted: Wed Sep 02, 2015 5:47 pm Post subject: |
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I'm looking at that SBD (and thanks Moto!). Yes, the bottom side is symmetrical, unlike the top. I guess I'm just having a hard time with the stresses of a full tank always pulling on the welded joint, instead of on top it would still have the flange supporting it. Have to think on this - I know with a good welded flange it "should" make no difference.
Jeff
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joescoolcustoms
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Joined: August 08, 2006
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Location: West By God Virginia
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| Posted: Wed Sep 02, 2015 8:01 pm Post subject: |
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I have beat the hell out of mine off roading in CA, UT and back home in WV. almost 22,000 miles crossing the US twice. It holds a touch over 12 gallon, so more weight than a stock size. No problems. I fill it up into the filler neck and roll down the highway.
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Bad News Racing 2018 NORRA 1000 3rd in Class
Best Day Ever Racing 2022 NORRA 1000 2nd in Class and first All Female team to complete the race
Everyone is gifted. Some just do not open the package.
Looks like it was painted with a live chicken,polished with a brick and buffed with a pine cone |
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motoRAT
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Joined: May 05, 2013
Posts: 308
Location: Portugal
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| Posted: Thu Sep 03, 2015 2:18 am Post subject: |
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GS guy, Strong the weld is, fear not you must 
hey joescoolcustoms, me likes it
OK, no more star wars 
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GS guy
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Location: Maryland
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| Posted: Thu Sep 03, 2015 3:51 pm Post subject: |
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 Moto-Yoda
Joe - your fab work is always an inspiration!
I'll post more pics up as I dive into this tank mod.
Thanks guys,
Jeff
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SBD
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| Posted: Thu Sep 03, 2015 8:30 pm Post subject: |
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| GS guy wrote: |
| ..Yes, the bottom side is symmetrical, unlike the top. I guess I'm just having a hard time with the stresses of a full tank always pulling on the welded joint, instead of on top it would still have the flange supporting it. Jeff |
I'm with you on that. I was thinking the same thing when I was posting earlier but figured, even if the entire weld failed and the whole bottom of the tank fell out, what's the worst that could happen??? 
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"Just $99 down and $64 a month for 36 months buys you a brand new Volkswagen Beetle!"
| mark tucker wrote: |
| I wouldent waste $ or thyme on building a small motor. build it big so it dosent have to work hard.remember it's only as fast as your foot alows it to be unless you build a small turd then it just stinks as it squishes up through your toes when you step on it. |
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motoRAT
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Posts: 308
Location: Portugal
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| Posted: Fri Sep 04, 2015 2:17 am Post subject: |
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| SBD wrote: |
| if the entire weld failed and the whole bottom of the tank fell out, what's the worst that could happen??? |
no more go go power after an espectacular ball of fire and sparks, burning man style
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GS guy
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Location: Maryland
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| Posted: Fri Sep 04, 2015 2:08 pm Post subject: |
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Thinking about this a bit (uh oh!), I'm back on snipping from the top. The bottom appears to be slightly smaller in overall dimensions at the flange (but is more symmetrical). If I cut along the corner joint where the metal curves up from the flange, It'll leave a "shelf" underneath to butt back against when it goes back together. Also, I'll be able to test-fit the bottom back into the car while adding new outlets, baffles, etc. since the flange will still be attached. Only thing happening to the top is sealing off the original inlet and adding a center-fill tube. A 2.25" steel tube fits perfectly with my Aero filler.
Just for fun I have to complicate it with an opening hood. Aero cap will stay with the tank when hood opens. More "schmit" to figure out! 
The (unsuspecting) patient:
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GS guy
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| Posted: Tue Sep 08, 2015 1:46 pm Post subject: |
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I'm needing some "school'n" on best practices on venting a modified VW tank. While I'm in there I want to be sure to add any new NPT or other bungs for getting the fuel out as well as venting back in.
I'd like to get ideas on adding vent/rollover valves and routing of the vent line. I've been googling rollover valves, not sure if an in-tank or remote would be best? Seems most are designed for fuel cells with all AN fittings. I'd prefer to stick with NPT fittings and hose nipples. Also read about a "double action" valve that vents normally, can seal up with a full tank to prevent vent-line dumping, and also has a roll-over shut off feature. This seems like something I could use? Just haven't found one of these with the right connections.
Looks like the high-point in the tank will be new center-fill neck or the raised ridge at the front of the tank. Not much head-room above that ridge - should I vent at the filler instead? Add a second riser for the vent?
I'm wide open to suggestions!
Jeff
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