How are the factory dual saddle fuel tanks supposed to be routed?

[WranglerTJForum]

for your purpose, i would only use the 87 switch if youre using the pollak valve and using baffled tanks for the in tank pumps

The switch above is for switching the sending unit most likely

I thought that might be the case, but then that begs the question, where on my 73 is the switch to engage each tank? Near as I can tell I’ve only got that one switch.

I’m going to use the 87 style Pollack valve and switch. My tanks aren’t baffled but with those Holley in-tank pumps and the HydraMat that should take care of that problem.

 

[WranglerTJForum]

That switch shown in post #13 is exactly like the one was in my 75 K20 with the added on left tank. Controlled everything and worked beautifully for 30 years..... til I removed it.......bad idea.....you can ALWAYS use fuel in a Square

So that switch on yours handled both switching of the tanks and sending units all in one switch?

It seems that there is so much variation in regards to how these worked over the years. I’ve even seen some earlier models that had manual valves under the seat that you had to twist in order to open up one tank or the other.

 

[Broken85]

That looks like the right valve. Yes, you only need the 3 port. The 6 port is for feed, and return on a mechanical system. You can use the 6 port, you just have to plug 3 of them because you don’t need a return. You can tie the vents from both tanks together with T-barbed fitting, they don’t need to go through the pollack. The switch that comes with the kit will probably work fine. The pollack valve also switches the fuel gage from left to right as well. If you are going to use a stock switch, it might be just worth getting a wiring harness off a donor truck. If you are going to wire it yourself, there is really no benefit getting a stock switch over using the one that comes with the kit since you will need to cut a square hole in the dash to use it.

I actually don’t think your switch and set up is a factory installation. I am not aware of GM placing them down there or ever looking like that, but if I am wrong, someone will correct me. I do know that most squares come with a 3/8 hole down there so the PO probably just repurposed it.

Fuel line supply is 3/8 hose, return lines are 5/16 and vent lines are 1/4. Below will help you understand how the switch works the pollack valve.

They say that you don’t need a baffled tank, but I think that is BS. My 12-308 will only pull 12 of the 16 gallons before they start sucking air. It is kind of frustrating loosing 25% of my fuel capacity. Take Aurora Girls advice. One day I will replace them but only when I get tired of stepping on legos or stubbing my toe.

 

[AuroraGirl]

I thought that might be the case, but then that begs the question, where on my 73 is the switch to engage each tank? Near as I can tell I’ve only got that one switch.

I’m going to use the 87 style Pollack valve and switch. My tanks aren’t baffled but with those Holley in-tank pumps and the HydraMat that should take care of that problem.

your setup would have simply actuated the solenoid if it used one, to direct the tank, if it didnt have a sender, then it was only doing that

 

[AuroraGirl]

That looks like the right valve. Yes, you only need the 3 port. The 6 port is for feed, return and vent on a mechanical system. You can use the 6 port, you just have to plug 4 of them. You can tie the vents from both tanks together with T-barbed fitting, they don’t need to go through the pollack. The switch that comes with the kit will probably work fine. The pollack valve also switches the fuel gage from left to right as well. If you are going to use a stock switch, it might be just worth getting a wiring harness off a donor truck. If you are going to wire it yourself, there is really no benefit getting a stock switch over using the one that comes with the kit since you will need to cut a square hole in the dash to use it.

I actually don’t think your switch and set up is a factory installation. I am not aware of GM placing them down there or ever looking like that, but if I am wrong, someone will correct me. I do know that most squares come with a 3/8 hole down there so the PO probably just repurposed it.

Fuel line supply is 3/8 hose, return lines are 5/16 and vent lines are 1/4. Below will help you understand how the switch works the pollack valve.

They say that you don’t need a baffled tank, but I think that is BS. My 12-308 will only pull 12 of the 16 gallons before they start sucking air. It is kind of frustrating loosing 25% of my fuel capacity. Take Aurora Girls advice. One day I will replace them but only when I get tired of stepping on legos or stubbing my toe.

do not plug ports on the 6 port
You should use the return functionality and a new pump for driveability

 

[WranglerTJForum]

That looks like the right valve. Yes, you only need the 3 port. The 6 port is for feed, return and vent on a mechanical system. You can use the 6 port, you just have to plug 4 of them. You can tie the vents from both tanks together with T-barbed fitting, they don’t need to go through the pollack. The switch that comes with the kit will probably work fine. The pollack valve also switches the fuel gage from left to right as well. If you are going to use a stock switch, it might be just worth getting a wiring harness off a donor truck. If you are going to wire it yourself, there is really no benefit getting a stock switch over using the one that comes with the kit since you will need to cut a square hole in the dash to use it.

I actually don’t think your switch and set up is a factory installation. I am not aware of GM placing them down there or ever looking like that, but if I am wrong, someone will correct me. I do know that most squares come with a 3/8 hole down there so the PO probably just repurposed it.

Fuel line supply is 3/8 hose, return lines are 5/16 and vent lines are 1/4. Below will help you understand how the switch works the pollack valve.

They say that you don’t need a baffled tank, but I think that is BS. My 12-308 will only pull 12 of the 16 gallons before they start sucking air. It is kind of frustrating loosing 25% of my fuel capacity. Take Aurora Girls advice. One day I will replace them but only when I get tired of stepping on legos or stubbing my toe.

Awesome, thanks again for the helpful advice! The more I read those diagrams the more I understand how this works.

I’m going to make my own wiring harness. Fortunately I’m very good with wiring so that won’t be an issue. I can make something clean unlike this rats nest that the previous owner left behind. I can’t stand bad wiring. As for the switch, maybe I’ll see if I can use the one that comes with the Pollack valve and fit it into that factory location.

If I am going to need baffled fuel tanks, are there any manufacturers that make baffled fuel tanks in polyethylene for these trucks? Mine current has the 16 gallon tanks on each side. May as well just order new tanks and do it all at once and do it right the first time.

 

[idahovette]

Yes , what I am saying is the switch that @WranglerTJForum shows is an aftermarket add on and that toggle is what controlled the whole system. Right side is constant and the toggle switches power to the left side along with the tank senders. IIRC the addon(left) tank was 25 gallons......always ran that one down then switched to the stock tank and started hunting for a station.......K20 with a 9 1/2 foot Kit self-contained overhead camper.......We went EVERYWHERE in that rig.....from Idaho to the Oregon Coast, to New York City and points between.......you HAD to have an abundance of FUEL!!!

 

[xm20k]

Oof I just tossed some of the dual tank stuff I pulled from mine when I swapped over to the fuel cell except the 3 port valve and 2 port sending units because they are new the harness etc went in the scrap.

 

[Broken85]

Awesome, thanks again for the helpful advice! The more I read those diagrams the more I understand how this works.

I’m going to make my own wiring harness. Fortunately I’m very good with wiring so that won’t be an issue. I can make something clean unlike this rats nest that the previous owner left behind. I can’t stand bad wiring. As for the switch, maybe I’ll see if I can use the one that comes with the Pollack valve and fit it into that factory location.

Believe it or not that switch is a factory switch. I saw on one of the other forums where they were discussing this. Apparently, it only came on some of the very earlier model trucks.

If I am going to need baffled fuel tanks, are there any manufacturers that make baffled fuel tanks in polyethylene for these trucks? Mine current has the 16 gallon tanks on each side. May as well just order new tanks and do it all at once and do it right the first time.

New tanks are like $100 and after spending $1,000 on two new pumps, it is cheap insurance. I don’t have any info on poly tanks. I bought two off of Jegs for $90 each.

 

[WranglerTJForum]

New tanks are like $100 and after spending $1,000 on two new pumps, it is cheap insurance. I don’t have any info on poly tanks. I bought two off of Jegs for $90 each.

Any idea which ones you bought?

I was looking at Jegs last night and none of them said they are baffled. Unless they are and they just don’t advertise it:

https://www.jegs.com/webapp/wcs/stores/servlet/SearchResultsPageCmd?pageSize=30&Tab=SKU&storeId=10001&catalogId=10001&langId=-1&year=1973&make=CHEVROLET&model=K10+PICKUP&submodel=BASE&engine=V8+(+5.7L+%2f+350+)&sbv=true&fq=category%3A10267&fq=PartTypes:Fuel+Tank

 

[Broken85]

Those might be the ones I bought. The ones I got were not baffled. I believed Holley when they said they didn’t need to be to baffled to work with the 12-308. Don’t fall for it like I did.

Also, if your is a short bed, the 20 gallon tanks won’t fit

 

[WranglerTJForum]

Those might be the ones I bought. The ones I got were not baffled. I believed Holley when they said they didn’t need to be to baffled to work with the 12-308. Don’t fall for it like I did.

Also, if your is a short bed, the 20 gallon tanks won’t fit

Oh okay, I misunderstood you then.

I’m stuck with the 16-gallons, you’re right. Now I’ve just got to find some that are baffled. All the ones coming up are non-baffled. I’m going to take your advice and do it right the first time.

Because before you even said anything I too was believing what Holley was saying about not needing baffles with the HydraMat.

 

[Ricko1966]

GM never used two different Pollack valves. The pollack valves on the 87’ and the pre-87’ are the same and can handle constant power when switch or momentary power. I used this as a trigger wire for the relay to activate the pump in the correct side. I am not sure if the pre 80’ can handle constant voltage, but maybe.

I thought the 3 port was early

 

[Ricko1966]

That looks like the right valve. Yes, you only need the 3 port. The 6 port is for feed, return and vent on a mechanical system. You can use the 6 port, you just have to plug 4 of them. You can tie the vents from both tanks together with T-barbed fitting, they don’t need to go through the pollack. The switch that comes with the kit will probably work fine. The pollack valve also switches the fuel gage from left to right as well. If you are going to use a stock switch, it might be just worth getting a wiring harness off a donor truck. If you are going to wire it yourself, there is really no benefit getting a stock switch over using the one that comes with the kit since you will need to cut a square hole in the dash to use it.

I actually don’t think your switch and set up is a factory installation. I am not aware of GM placing them down there or ever looking like that, but if I am wrong, someone will correct me. I do know that most squares come with a 3/8 hole down there so the PO probably just repurposed it.

Fuel line supply is 3/8 hose, return lines are 5/16 and vent lines are 1/4. Below will help you understand how the switch works the pollack valve.

They say that you don’t need a baffled tank, but I think that is BS. My 12-308 will only pull 12 of the 16 gallons before they start sucking air. It is kind of frustrating loosing 25% of my fuel capacity. Take Aurora Girls advice. One day I will replace them but only when I get tired of stepping on legos or stubbing my toe.

When I said early and late I should have said return or no return. Wasn't thinking. But now that I am he needs to verify whether his injection requires a fuel return,it probably does. If so he's going to have to go with the later style valve.

 

[Broken85]

I thought the 3 port was early

Yep, I think you are correct. I just meant there wasn’t a different pollack valve for just for the 87’ models. It was the same as the identical years. The round eyes had that valve I believe but I never owned a dual tank pre-1980, just single tanks