Fuel tank replacement on 1987 LS swapped square body

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Squareondabayou

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1987
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LS1
Hi guys, kinda new here. First post so be gentle. I have a 1987 C10 with an LS 1 swap. I need to replace passenger side tank so I am just going to swap both of them while I am at it. My question is what is what parts do I need to complete the job? I have a mechanic that is going to do this for me but I need to order everything for the job. I have looked online and I am a bit overwhelmed at what I am seeing. I also want to replace the switching valve for the tanks as well. Do I need new fuel pumps? Thanks for your input.
 

aasleson

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Welcome!
The parts required depend on how your Fuel system is set up, most common is to use the 87 Fuel tank and run an ls Fuel pump in the tank. Beings as yours is an 87 I'd assume they reused the factory tank. In my opinion for the pumps and tank selector if there is no issue with it I would reuse what's there. If you must replace the tank selector valve holley makes a pressure rated tank selector P/N: 534-39
 

Squareondabayou

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Thanks for the info. I am pretty sure these are the original tanks. This all started when I switched to the passenger side tank and fuel started leaking out. I took it to my mechanic and he said that he was worried when he dropped the tank that there may be more than a gasket issue. He is very experienced with these trucks as he has a mid-70's Blazer that he did a frame off resto mod on. It was my decision to go ahead and replace both of them while he was doing the repair so I can check that off the list
 

crysalis

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I just finished both of mine on my '85 over the weekend. Granted, I dont have EFI like yours, but if you're gonna do it, prepare to do most of it. It wasn't hard, but wasn't fun.

I did both tanks, both sending units, 3 hoses each (supply, return, vent) between each sender to the metal lines (going to Pollak valve). When they drop the tanks, there is only a few inches of fuel line, and will need cut (at least for factory pre-EFI setups). I put two feet of each line on each tank so that putting the tank back up is easier. 3 of 4 of my brackets were completely rusted out, so I replaced all of them with new bracket/straps and rubber squeak prevention (I used rubber strips from flooring department). You may also need the fuel neck assemblies to go from the tank to the bed - mine were swiss cheese.

I didn't replace the Pollak valve as I've never used it since owning the truck... maybe it works, maybe it doesn't. I also didn't reinstall the plastic rock shield for the tanks.

If you need brackets/straps, make sure to order 2 front and 2 back. Also, be aware that the fronts have different bolt patterns for each side. If you order front brackets that does not have nuts welded on, your installer will need to weld some 3/8-16 nuts on to the bracket.

You can find almost everything you need from LMC, with exception of 16 gallon fuel necks. If you have 16 gallon now, I would suggest changing to 20 gallon. Parts are easier to find. I wasn't aware of this until after I bought the 16 gallon tanks.
 

Camar068

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or put a 'burb tank under the bed back by the bumper.

An option. 1 tank, fuel pump, sender, and lines. Hardest part is figuring out where to put the filler.
 

aasleson

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Thanks for the info. I am pretty sure these are the original tanks. This all started when I switched to the passenger side tank and fuel started leaking out. I took it to my mechanic and he said that he was worried when he dropped the tank that there may be more than a gasket issue. He is very experienced with these trucks as he has a mid-70's Blazer that he did a frame off resto mod on. It was my decision to go ahead and replace both of them while he was doing the repair so I can check that off the list

Is he sure its an issue with the tank and just not a fuel line leaking at the sending unit?
 

goldpack

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what donor did the LS1 come out of? ...do you have that vehicle to pick off?
 

Squareondabayou

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Not really sure of the vehicle as I purchased it after the swap from North Carolina.
Also, my mechanic said he wasn't really sure of where the leak was coming from but judging from the amount of fuel leaking he had his suspicions. He is a very good friend of mine so he is not trying to up sell me or anything. He did say that he has come across a few cases of going into it thinking it was just a gasket or fuel line and it turned out to be corrosion on top of the tank. I don't want to be held up waiting on parts and tying up his lift at his shop waiting on parts so I was just going to replace both and try and eliminate this situation going forward. We drive the truck to shows and such and I don't want to deal with this issue. There are plenty other issues that pop up as it is.
 

goldpack

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CountKrunk

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He can't look at it and know what parts to get? Surprised he wants you to figure that out then him install.
 

Bextreme04

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I removed both saddle tanks, replaced all rubber hose and both sending units and re-installed them all in about 2 hours. In a gravel driveway. I would put it on the lift and check everything out before deciding what to order. Tanks are easy to find and cheap. Sending units are not. The holley switching valve is probably worth having on an LS swap regardless. The most likely thing for someone to have done on an LS swap is to have just replaced the factory 12 PSI TBI fuel pumps with AC Delco EP381 pumps and send it.
 

Broken85

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Replacing the tanks is just good hygiene for the motor. After 40 years, and at $90 each, it’s a no brainer. I would expect you have a bad fuel line, but if you are taking them down, I agree with your buddy and just replace it. Also agree with ditching the rock guards. Those were one of GMs worse ideas. I think they put them in the truck just to sell more fuel tanks. Also agree if it’s a long bed, just upgrade to 20 gallon tanks

I can’t give you any suggestions on pumps, but they can range from $100 if you are using the stock ones to $400ish if you buy some wiz-bang Holley options. Not sure what your motor needs. New hoses are an obvious must. You will need 3/8 for the supply, 5/16 for the return and 1/4 for the vent. The switch valve is up to you. I know Holley offers a “high pressure” switch valve option but I am not sure if there is any real difference. GM did not change them from 86 to 87 when they went from carbureted to FI. I have had a $60 Napa on mine for two years with no problem in between my Holly Sniper and a pair of Holly 12-308’s. Holly’s valve for $135 seems a little unnecessarily steep. I replaced mine just because it was 40 years old, but my original was still working fine.

Good suggestions on the tank mounts and straps. The saddles will start to add-$$$-up, but the straps are cheap. You can probably reuse your fill necks.

Check the grounds on the fuel gauge when you are in there.
 
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