1968 Dodge Polara C-Body Gas tank conversion

[blackmamba]

Hello fellow C-Body Brothers! Has anyone installed the 1970 Dodge Charger Flip open style Gas Cap, Filler Neck, and Gas Tank on a C-Body Car? I'm looking at doing this on my 1968 Polara Coupe. The tank Swap is what concerns me, mounting points for hangers etc.

 

[Fratzog]

I have a 68 Monaco 500 but it has never occurred to me to try such a modification since I'm more conservative when it comes to mods. It would be surprising if you found someone who has tried this so you may be breaking new ground. I will watch this thread with interest.

 

[MrMoparCHP]

I'd buy a new tank for the Polara and have the opening moved as needed. If the existing tank is in good shape a good shop should be able to move the opening.
The amount of work to put a E-Body tank may not be worth it and you'd be going from 23 gallons to 16


Alan

 

[blackmamba]

I'd buy a new tank for the Polara and have the opening moved as needed. If the existing tank is in good shape a good shop should be able to move the opening.
The amount of work to put a E-Body tank may not be worth it and you'd be going from 23 gallons to 16


Alan

I'd buy a new tank for the Polara and have the opening moved as needed. If the existing tank is in good shape a good shop should be able to move the opening.
The amount of work to put a E-Body tank may not be worth it and you'd be going from 23 gallons to 16


Alan

Hello! I'm a Retired Journeyman Nuclear Steamfitter Weldor LU-598. The repositioning of the gas cap for the Polara is pretty straight forward. Yeah the 16 gal is not acceptable. I might end up modifying the new polara tank by changing the filler neck opening then plumb it to Charger spec's.

 

[68 4spd Fury]

Interesting thought. The caps as I remember, were recessed into the sheet metal, nothing a good body person couldn't make happen. It may need to be a side mount, like the 67-69 A-body Barracudas, you may not have enough flat area near the trunk to have it on top like the Chargers. As mentioned in previous comments, modifying a new tank for the car would be the way to go, a 68-70 charger tank may not fit as well, either way the filler neck would need to be fabricated. Good luck, like to see the results.

 

[CBODY67]

Seems like there was a convertible from Canada that had had that mod done, for sale in here, a month or so ago? Key thing would be the flatness or curvature of the sheet metal on your car matching or being made to match what's needed for the Charger's item. A few little details like "rain drain" and such for any liquid to drain from the recesses of the Charger's cap, might need some additional plumbing.

Just some thoughts,
CBODY67

 

[fury fan]

Also consider that you'll hafta be careful *every* time you fill up to not spill gas on the paint.
The filler-neck-to-tank piping might be fabbable by a local muffler shop, then have them weld suitable flanges on both ends?
Source as many of the Charger parts as you can to see what you can re-use.

Make sure to tell a few Charger guys you're stealing their stuff for a C-body.

 

[blackmamba]

I'd buy a new tank for the Polara and have the opening moved as needed. If the existing tank is in good shape a good shop should be able to move the opening.
The amount of work to put a E-Body tank may not be worth it and you'd be going from 23 gallons to 16


Alan

 

[blackmamba]

Hey just a big shout out THANK YOU! to all you guys for your comments and advice. I just turned out the lights in the shop, Tomorrow I'm doing it!!!! LOL!

 

[blackmamba]

Good Morning C-Body Brothers and Sista's! Just received the flip top gas cap parts from Vans Auto LLC. The 1968 Monaco 383 cu in, A-727 TRANS. This was my first resto on my Dads car which hooked me on C-Body's. Runs like a "Raped Ape" For those of you Kat's that dig the Jive! My 67 Polara which shares much of the same body style will receive this modification.

 

[fury fan]

I know that's where it has to go, but watch that spot!
There's a brace that runs from the wheelhouse up to either the quarterpanel or Dutchman, and the trunk hinges in that area too. It might be tough to get around/through that.
However you plan to do it, check for clearance with trunk open and closed to see where the hinges must travel.
You will also have to decide on your tubing routing with respect to spare tire storage. It may end up as a somewhat complex pipe.

If you end up making this pipe as a welded fabrication, either yourself or from a muffler shop, any weld areas are a potential for rust to get into your fuel tank. Yes, your filter sock in the tank and the filter at the engine should catch this, but it's something to be aware of and make a risk-assessment decision on.

 

[fury fan]

Also -
Remember that you are now piping fuel thru the trunk area, and there is no fume/firewall between trunk area and the interior of the car. A standard tank location/fill outside of the trunk cavity has this covered. The Charger installation does also, but the components were factory-validated to be safe. Make sure you follow their pattern to as many details as possible, and to understand the risks of anything you change on your own. Pay attention to things that need to have relative motion. FMEA - Failure mode and effects analysis!

A retired nuclear guy probably has it handled, but I often type things for other people who visit these pages later on.

 

[blackmamba]

Also -
Remember that you are now piping fuel thru the trunk area, and there is no fume/firewall between trunk area and the interior of the car. A standard tank location/fill outside of the trunk cavity has this covered. The Charger installation does also, but the components were factory-validated to be safe. Make sure you follow their pattern to as many details as possible, and to understand the risks of anything you change on your own. Pay attention to things that need to have relative motion. FMEA - Failure mode and effects analysis!

A retired nuclear guy probably has it handled, but I often type things for other people who visit these pages later on.

 

[blackmamba]

Hello! Thank you for the insight! My Fitter and I looked at this like a Nuclear install LOL! We plan to run 2 inch Stainless tube and open root Tig weld the joints. We looked at using the existing tank by bobbing the filler neck behind the bumper, under the trunk turn a 90 to the left rear corner, turn a 90 toward the front, then short run under the floor 90 up through trunk floor through rubber filler neck seal. Then up to gas cap. Vent tube follows same run along tube.

 

[commando1]

I think the effort should be directed at rust repair first but if you insist...

[FOR SALE] - Ask and you shall recieve! (Flip Top Gas cap Adapter)

 

[blackmamba]

I think the effort should be directed at rust repair first but if you insist...

[FOR SALE] - Ask and you shall recieve! (Flip Top Gas cap Adapter)

 

[blackmamba]

Hello! Ah the Monaco! Yes right you are on the rust issue. This paint job was done in old barn 1985 "Roadkill Style" We skinned the peeling Vinyl top found extensive rust all around the bottom of it. Used Por-15 on everything! 7 years later blisters started showing up. Yes it go's in the shop this spring for more extensive body work.

 

[fury fan]

Hello! Thank you for the insight! My Fitter and I looked at this like a Nuclear install LOL! We plan to run 2 inch Stainless tube and open root Tig weld the joints. We looked at using the existing tank by bobbing the filler neck behind the bumper, under the trunk turn a 90 to the left rear corner, turn a 90 toward the front, then short run under the floor 90 up through trunk floor through rubber filler neck seal. Then up to gas cap. Vent tube follows same run along tube.

The pipe construction/materials sound awesome for this use, and bypasses the rust concern.
But I would not route it that way, here's my rationale:

• That's an awfully long run of pipe.
• It's going to route thru your tailpipe area (I assume you'll have dual exh) and make routing a tailpipe harder, then you hafta make the other side match that one (could be double-trouble).
• Biggest reason - you'll likely not have a good downhill run for the entire length of pipe, specifically by the gas tank, and if you don't, that will probably make a low spot that is lower than the tank inlet behind the license plate. You want the entire run of pipe to be higher than the tank inlet so that you never have a puddle of gas in a low spot. As the tank's original inlet is in the top half of the tank (and it's a much shallower stamping than the bottom), I don't think you can get a downhill angle while you're running beside the tank. You don't want a P-trap.

You hafta penetrate the trunk are no matter how you install this cap, so I would recommend the shortest, steepest run possible.

Perhaps you could incorporate the tank inlet into a fitting into the fuel sending unit? Whatever that is would need to outflow a gas-station pump, though, and that'll be tough with only head pressure of the fuel.

Or maybe weld a dedicated flange/nipple onto the vertical section of tank to the driverside of the fuel sender, that connects to your filler tube via a rubber coupling?

Or here's a crazy idea, way outside the box. It solves some issues (allows you to use smaller hose) but creates new hurdles:

• Pipe the fuel filler tube into a 'catch can', install an electric pump in the shock absorber area below it, pump the fuel into the tank into a #8 fitting in your fuel sender, or maybe a #10-#12 bulkhead fitting in the tank beside the sender. Or run that back into the original filler neck somehow.
• The catch can could be just a large section of pipe with a fitting at the bottom, and you have a switch located in the trunk hinge area to run the pump while you fill up.
• The big problem there is making sure you don't under-pump the catchcan and splash gas on yourself, or overpump it and run the elec pump dry too often. Theoretically the gas station pump should shut off and not splash you, but we know that isn't 100% trustworthy.
• With this idea, again, think FMEA big-time.

 

[ImpJay]

I´m not 100% sure, but think that someone has a flip top gas cap on a 67-68 Polara or Monaco on this side of the ocean. It´d be a blue or grey 2dr, if it was real.

 

[blackmamba]

I´m not 100% sure, but think that someone has a flip top gas cap on a 67-68 Polara or Monaco on this side of the ocean. It´d be a blue or grey 2dr, if it was real.