85 K20 Dual Fuel Tank 16 to 20 gallon conversion?

[sick472]

It's time to work on my 85 K20 fuel tanks. It has duel 16 gallon tanks and one of them is leaking due to a rusted frame bracket and a hole in the bottom while the drivers side will not supply fuel (maybe an electrical problem as I have already replaced the dash switch and selector valve.

I plan on pulling the bed to trouble shoot the drivers side issues and I might as well convert to 20 gallon tanks while I'm at it.

Will the 20 gallon tanks swap in easy enough? Any tricks you could share?

[86454k30]

Parts needed that I am aware of.

20 gallon tanks
Fuel fill hose(s)
Fuel fill vent hose(s)
Fuel fill neck(s)

[sweetk30]

that list seems right . i just did this on one last year . the frame bracket on the rear position just moves to the extra holes in the frame .

with new bracket make sure you weld the nuts on the bracket to help in the install . and there universal left to right so mock it up first to see what holes to mark to weld the nuts on . i didnt watch on one i did but got lucky and swapped sides and got away with it .

i also use tar paper for house roofing jobs as the anti squeak pad between the tank and brackets .

[Dead Parrot]

Might plan on new frame brackets and straps. If one is rusted out, good chance the others aren't far behind.

Make sure the fill pipes on the new tanks match the size of your existing fill receptacles. IIRC - the earlier tanks had larger hoses. Possible some PO swapped in earlier parts.

Probably a silly question but it is a long bed?

[old Rusty C10]

I don't know what your skill and tool availability is but my brackets rotted right at the bottom and we were able to get straps at advance auto parts and then make the patch to fix the old brackets.. they worked well

[sick472]

Thanks a million for your responses...you folks are great! Now, it's time to save some time and money as all the items I will need will be a bit spendy if I go "all the way".

I think I read that the tanks can swap sides??? If that is the case, I might put the driver's side good 16 gallon tank on the passenger side and just buy a 20 gallon tank for the driver's side. I'm tired of filling up so often AND having to walk around the truck to get to the "good" tank (than now seems to have a small leak).

[Dead Parrot]

IIRC - the tanks can be swapped. The senders can't.

[sweetk30]

tank and the brackets are left/right swappable unless the nuts are welded to the brackets then you just work around that .

i got my spectra premium tanks off ebay cheeper than any were i found from the popular stores and web sites .

[sick472]

Thanks a million for everyones help. I got the job done and all is good now. Those plastic covers should be outlawed! Once I got both tanks removed, there was very little left of the tank brackets and straps and all that added up too more than I cared to spend on the fix so I had to spend time refurbishing them using steel from the scrap pile out back. Those covers collected and held sand and dirt which ultimately rusted out the one tank and all the brackets. My truck is now part recliner (steel from the guts of grandma's old lazyboy...lol). I added some strip steel to reinforce the straps, acid washed the works and laid some industrial enamel on so thick that the parts could outlast time. At anyrate, it's amazing how much you can sink into rebuilding a dual tank system if you had to replace it all...I now have a 20 gallon on the drivers side, moved that good 16 gallon tank to the passenger side, new sending units, and it all works like it should! I found out why the drivers side never worked...pinched feed hose at the sending unit. Someone did a sending unit job on that side without remvoing the bed and couldn't see what they were doing hence pinching the hose. I bet they were po'd to do the work and get the gas gage to read proper, but then lose the function of that tank.

Thanks again! Here are a few pics for those that skipped my long winded "thank you".

[Keith Seymore]

Looks good -

What was the motivation for going blue (rather than black)?

K

[sick472]

Originally Posted by Keith Seymore

Looks good -

What was the motivation for going blue (rather than black)?

K

I happen to of had some left over blue and I'm tight that way.

Now the blue is gone and the only paints left in my stash is safety orange and yellow and a johndeere green. Who know's what will need painted next...I hope it's not on the exterior of the truck...lol.

[sick472]

A fellow member has asked me to post some photos of the hole locations for the 16 and 20 gallon tank brackets. Just for the record...the rearward brackets will be in a different location, but they do share two of the holes regardless of the bracket location (circled in red AND green). These photos show that. You can even see where the 16 gallon bracket holes where used on the driver's side by the witness marks from the washers. These photos are of the rearward most holes. The forward sets will be the same regardless of the tank size. If, for some reason, your frame does not have the extra holes...it should be pretty easy to use the shared holes to mirror the markings for the new holes. Here's a tip...make the hole for the strap threaded section about 3/8" larger than stock so that it is easier to get a socket in there to tighten the straps. I got it done with some fussing, but just a bit bigger hole would have made it easier.

The first pic shows the passenger's side with a 16 gallon tank and the second is of the driver's side with the 20 gallon tank...

[Getter-Done]

Great info in this Thread.
I can Add one thing.
Use anti-seize on those bolts.







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