what would you do

[MEMO43]

ok rig first 85 k20 sbc 350/ th400 208.
I'm debating removing both my saddle tanks, and doing a blazer or suburban tank swap.
I have replaced the sending unit on the pass side, selector valve, dash switch. still need the driver side sending unit an tank ( has some sort of puddy to fix a hole)
I plan on doing efi swap down the road an would rather pull from one tank than go through the hassle of pulling from two tanks.
plus the weight over the axles.
what would you do

 

[Bent77]

Single 31 gallon tank, needs its specific sender for EFI and depth

made the change 4 years ago. Should have done it sooner

the only real thing to sort is the filler neck
I ran the hose to the bedside and relocated the filler there. Works great

 

[MEMO43]

thanks for the reply @Bent77
I'll browse through your builds an see if there's any pics of how you set you fill neck.
my rig is a DD with occasional trail rides

 

[Joel Wilson]

ok rig first 85 k20 sbc 350/ th400 208.
I'm debating removing both my saddle tanks, and doing a blazer or suburban tank swap.
I have replaced the sending unit on the pass side, selector valve, dash switch. still need the driver side sending unit an tank ( has some sort of puddy to fix a hole)
I plan on doing efi swap down the road an would rather pull from one tank than go through the hassle of pulling from two tanks.
plus the weight over the axles.
what would you do

That's a tough one. I've had a 76 and an 85 with saddle bags and my 77 Jimmy has a rear tank. Yes you have twice the headaches with saddle bags, but you have that redundant backup if you have a problem with one tank. If you have a problem with one big tank, you are a sitting duck. I seem to vaguely remember there being a surge tank fuel pump thing that you can mount in the engine compartment after the stock mechanical pump. The mechanical pump fed the surge tank and the electric pump pressurized the rail. Supposedly allows you to keep the stock fuel system while giving you EFI. Read it in some article somewhere but can't remember when or where.

 

[skunked]

the 31 gallon tank is a pretty straight forward install on the long bed.

I added a forward crossmember (1.25" sqaure tube IIRC) along with some anti squeak single sided HVAC tape you can find at Lowes. For the fuel tank straps I added a piece of angle iron on the forward side and drilled holes in the stock crossmember in the rear.

Plumbing

and the filler neck I use is 1.75" https://www.millsupply.com/unleaded-gas-filler-neck-81983.php?p=324357

It flows very well, so well I can walk away from it.

 

[1-ton]

The one thing nice about saddle tanks is if you have 20-gallon tanks that is 40-gallons of fuel versus 30-gallons in a single tank. I also would not be surprised if GM purposely designed the saddle tanks for proper weight distribution when it comes to load capacity of the suspension.

 

[ZooMad75]

Sitting duck with a single tank? No less a sitting duck to a dual tank setup with a switch valve that failed. I think there are plenty of blazers and burbs with single tanks that have way less issues than the dual tanks in the trucks had.

In terms of simplicity with an efi swap going to one tank makes it a lot easier. Someone has come out with a high pressure unit capable of more than TBI fuel pressures. Still that means two TBI tanks, higher pressure pumps, and some interesting fuel lines between the tanks and the switch valve. Sure there's a level of redundancy if one pump fails, but not if the switch valve does. You end up having more fuel lines/connections for possible leaks too.

 

[1-ton]

My 1991 V3500 crew cab pick-up with dual 20-gallon saddle tanks has TBI. I had the TBI unit modifeid by Vic Morse to include an adjustable fuel pressure regulator. I have a set of in tank AC/Delco fuel pumps that are used in cross-fire TBI units that have a max fuel pressure rating of 60-PSI. After doing some data logging I have found that my engine runs best with the adjustable fuel pressure regulator set to 12-PSI.

P.S. I do carry a spare tank switch valve with me when I go on any long distance or wheeling trips.

 

[Joel Wilson]

Sitting duck with a single tank? No less a sitting duck to a dual tank setup with a switch valve that failed. I think there are plenty of blazers and burbs with single tanks that have way less issues than the dual tanks in the trucks had.

In terms of simplicity with an efi swap going to one tank makes it a lot easier. Someone has come out with a high pressure unit capable of more than TBI fuel pressures. Still that means two TBI tanks, higher pressure pumps, and some interesting fuel lines between the tanks and the switch valve. Sure there's a level of redundancy if one pump fails, but not if the switch valve does. You end up having more fuel lines/connections for possible leaks too.

I never had the switch valve fail on my 76 or my 85. Not even after the 85 was T boned by a Mustang doing 55mph. Just not a fan of having a fuel pump in the tank. If you don't drop the tank to change the fuel pump then you have to cut a hole in your bed or floor board. And if you drop the tank, I guarantee it won't be when the tank is empty. So then you're back to having to cut into your bed which just allows more junk and crud to get in there which means rust. And if you go from dual tanks to a single tank, then you have to cut another hole in the bed for the filler neck. There are pros and cons to both ways.

 

[MEMO43]

Thanks for all the replies
so far between everyone's input an me crunching numbers
saddle tanks 100 (need to get both)
sending units 60 (bought one already)
selector valve 50 (already bought)
dash switch 15 (already purchased)
thats just shy of 400

one 31 gallon tank 110
sending unit 60

My rig was parked for 10 years before It followed me home.
really like @skusent up may end up doing something similar to his
now to wait for some warm weather an decide/plan on either inline pump or in tank pump.
Decisions Decisions
but hey at least I can still dream