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25 Gallon gas tank install

72K views 43 replies 20 participants last post by  teahead 
#1 ·
Classic Performance Products
Tri-Five Chevy High Capacity Fuel TankBy Steven RuppHere's the scenario: You've been wrenching on your '57 all winter long with the goal to long-haul the Hot Rod Power Tour. The A/C is charged, cup holders have been installed, and your rims are wrapped in fresh rubber. Your only concern is that the 572 big-block under the hood gets 15 mpg on the highway. This means you'll have to stop for gas every 240 miles, and you just know that fill-up time will happen when it's least convenient.You've thought about dropping a bigger tank, but you don't want to cut up your trunk floor, lose your spare tire or have some gigantic tank hanging down under your ride. The guys over at Classic Performance Products considered that exact scenario and started working on a way to drop a much bigger fuel tank into a Tri-Five Chevy.What they came. up with is a 25-gallon stainless tank to replace the 16-gallon factory unit. It looks better, and more important, it installs without having to violate the factory sheetmetal of your classic Chevy. For the guy knocking down 15 mpg, it will up his range from 240 to 375 miles. And that adds a lot of flexibility to your cruising plans.


Here's the original fuel tank as seen from under the car. In addition to being unattractive, it doesn't utilize the space efficiently.
After we disconnected the fuel hoses and mounting straps, the old 16 gallon tank is removed. However, we left the spare tire well in place. The goal is to increase tile size of the tank without cutting up the car.
Once all of the original fuel tank mounting hardware is removed, we put the new 25-gallon tank up in the chassis for a quick test fit. This tank is fully baffled, made from 1/8-inch thick aluminum and mounts on beefy 3/16-inch flanges. All of the CPP tanks are pressure tested before being shipped.
The new sending unit after it has been set up for this tank, pictured with a new sending unit as it comes out of the box.
Here you can see the sending unit mounted in the tank. This billet flange is already tapped for both of the popular sending unit bolt patterns. There are several sending units available to work with the OE and aftermarket fuel gauges.
First we mount the new crossmember under the car.
The cross member is a two-piece telescoping design that hangs off
of the top of the frame rails. It is assembled finger tight until it can be set into its final location.
A measurement is taken from the rear of the tank mount to the front of the tank mount.
Using the measurement taken from the tank, the new mounting crossmember is located the same distance from the rear-frame crossmember.
We do the final prep work before putting the new tank into the car. Here the vent fitting roll over valve is being installed. If any fuel stal1s to flow through this valve, it will automatically close, keeping the gas where it belongs in the tank.
Using the new crossmember as a template several 5/16-inch
holes are drilled into the frame. Then 3/8-inch self-taping bolts are installed to hold the crossmember against the frame rails.
After the crossmember is bolted tight to the frame, the two bolts that control the telescoping action are tightened. This design allows for variances in the distance between the frame rails.
With the crossmember in place and the vent hose attached, the new tank is raised into position under the '57.
Using the tank as a template, 3/8-inch holes are drilled into the rear crossmember.
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The tank is then bolted to the rear crossmember using these trick little nut plates that were included in the CPP kit.
Since this car has the original carburetor and fuel pump, one of the 3/8-inch fittings is plugged and the fuel line is connected to the other. If we add fuel injection later we can simply remove the plug and connect a fuel-return line.
A reducer is used to connect the new 1.5-inch kinkproof fuel-filler hose to the original fuel filler in the rear fender. The hose is routed through the original guide, then between the frame rail and trunk floor before it reaches the connection on the side of the fuel tank.


These two pictures show how the new 25-gallon tank fits between the rails next to the spare tire well and the Flowmaster exhaust system. The spare tire well, rear bumper, and rear fenders are all lower than the tank, so the tank can not be seen once the car is back on the ground. Even if your Tri-Five only knocks down 10 mpg, this tank will give you an extra 90 miles before having to pull over. Imagine the range if you have a fuel-sipping LS engine and a deep overdrive.
 
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#5 ·
#6 ·
I just ordered this 25 gallon tank from Danchuk for pickup this Saturday. After getting back from Reno and Hot August Nights this year the wife and I decided to go with a larger tank for her car which we will drive to HAN next year. The Bel Air got about 17 mpg on average for the whole trip and her 210 will get a similar MPG so I will get an extra 150 miles with the larger tank accounting for reserve. We needed a new tank anyway and this tank keeps the spare tire space AND mounts to the frame so I can run all of my lines without the body on. This is a win-win for us as the body is out at paint and not due back for a few months.

http://www.danchuk.com/ItemForm.aspx?item=15220A



 
#7 ·
I just ordered this 25 gallon tank from Danchuk for pickup this Saturday. After getting back from Reno and Hot August Nights this year the wife and I decided to go with a larger tank for her car which we will drive to HAN next year. The Bel Air got about 17 mpg on average for the whole trip and her 210 will get a similar MPG so I will get an extra 150 miles with the larger tank accounting for reserve. We needed a new tank anyway and this tank keeps the spare tire space AND mounts to the frame so I can run all of my lines without the body on. This is a win-win for us as the body is out at paint and not due back for a few months.
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Good luck with the tank- looks like a nice set-up. My Rick's tank is 3 gal less and wouldn't allow for a spare tire well (Though I'm still very pleased with it).
 
#8 ·
I'm a big fan of that tank, I've posted my praises here a few times. I would suggest removing the tank when you drop your body down as it is very tight betwen the spare tire well and tank. I had to "adjust" my well with a 3lb. hammer to lift the tank up. No biggie with my heap but your car is in another class alltogether! On my car once the tank was fully installed, the filler neck on the tank was resting firmly on the frame rail, no room to slide on the filler hose. My assistant is a welder and suggested notching the frame for clearance, which he did and solved that problem. Hopefully my situation is unique.
(there's plenty of room above the frame to angle up that neck a few degrees, they really should change it)

Good Luck, Gerry
 
#10 ·
We just finished the installation of the new 25 gallon CPP fuel tank from Danchuk. My friend James came over and we finished it up in two hours. I was VERY lucky that the hardware was already very close to the silver color of my wife's 210 frame!

The kit and parts are well made and I would recommend this tank to anyone who wants more range or for anyone who wants to keep their spare tire well. This kit should be installed with two people and make sure you have a couple of sharp 3/8" drill bits before you start.

A few pictures of the installation are shown below.







 
#14 ·
That 25 gal tank was well worth the investment, I love it.

I made an access cover in the trunk of my car so I can easily change the fuel pump sending unit etc, without removing the tank.

I cut an additional opening at the top of the tank to put in an electric fuel pump.

The tank has baffles in it, you can stand on the tank and it does not have any give at all.


It fit perfect, no mods needed


Otis :)
 
#15 ·
did i miss what sending unit is needed
 
#16 ·
#17 ·
I bought the jumbo 29 gallon for my wagon and will begin the install this week. I bought the universal 30 ohm sender and I'm thinking of putting in a cover and ring for a submersible fuel pump , just in case I might go to EFI in the future. I'd rather do this now as the tank is clean.
 
#18 ·
When we went to install the body back on the frame the old tank mounts were in the way of the new bracket so we had to cut those off. If you installed the kit with the body on it would have been apparent much earlier.

After we got the body on I cut about 7" off the original one piece 56' filler neck and used the included adapter, hoses and clamps to get it all back together. As a side note, I had the original bracket and filler neck/pipe powder coated in black while it was out of the car.

Once I get gas in it and get the wiring done in April I will continue the post with the gauge readings and final comments.









 
#20 ·
Funny place to mount the gas tank Tim.....Reminds me of the old Ford firewall mounted gas tank.


Never mind....I see you changed your mind :)

 
#24 ·
I just got my 25 gal tank and had a couple of questions:

1. Any concern with this being a bottom feed tank?

2. How are you guys plumbing the fuel line?


I was planning on running a 90 degree npt/an fitting and take a hard line vertical to the top of the tank, then bend the line to run over to the frame rail and off to the engine compartment.

Hopefully that would issolate any fuel line leaks forward the tank and I'd only have one set of fittings to deal with at the tank.

Please let me know. I'm just a beginner and want to make sure I get this right.
 
#26 ·
Well I got my tank bolted in.

I guess 56 years of crud and undercoat makes it a tight squeeze. But with some scraping, scrubing, and a little massaging with a hammer it just clears between the spare tire well and frame.

Not easy to put in all by yourself. But I managed.

Now I just need to connect the filler tubing and run the new fuel lines.

I did have a problem with the air vent fitting and the bottom of the trunk floor as well. But it all worked out...with a hammer.
 
#28 ·
ill be putting mine in someday hopefully soon
 
#30 ·
had a quick ? on the sending unit do you want it to install to one of the sides or front to back on the tank
 
#36 ·
How much clearance do you need from what you have now? Could you space the tank down enough without it being an issue? Or depending upon where it hits, make a strategic and small dimple to get the clearance you need? Just some thoughts to consider. Not sure either would be the solution but .........it sounds like this is darned close to a fit with perhaps a small modification that the tank would hide (well, depending on where it would show up on the topside if you chose the second option. I'm interested in what you end up doing as I'm considering the same swap.
 
#37 ·
saf57 i need about 1/4 in so i took a hammer to the floor so i think that will work. Its 110 in Phoenix right now so i am in no hurry to get out to a 112 degree garage to see how it fits! I will update with picture when i am brave enough to go out into the heat to install the tank
 
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