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Old 02-16-2021, 09:51 AM   #1
Xavier
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In-cab to under-bed fuel tank conversion questions

I've been collecting the parts to do an EFI upgrade on my '68 and was looking for some insight from other regarding fuel tank options.

I already have and plan on using a Holley Sniper EFI with a Holley in-tank Retrofit fuel pump module.

Using that setup I think I will still need a sending unit to get fuel levels, correct?

There are so many different tank options I'm not sure which would be best suited for my application. I definitely want a side filling tank.
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Old 02-16-2021, 01:27 PM   #2
MARKDTN
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Re: In-cab to under-bed fuel tank conversion questions

I put EFI on a '72 SWB for a guy about 15 years ago. Used an '86 S10 Blazer tank that had a 2.8 TBI. Swapped the pump for what I needed ('89 IROC pump). It has the correct resistance sending unit for the stock gauge. It has a side fill. On the truck I did, I notched the top of the frame for the filler neck. Somebody else put a (5th gen) stepside bed on it and made the filler on the passenger side.
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Old 02-16-2021, 02:56 PM   #3
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Re: In-cab to under-bed fuel tank conversion questions

Sounds like you have a good plan.
The hose issues will be hose type, hose routing and adapting the hoses.
Planing for the return, if required, and the vent.
These are the easy issues.
Figuring out how to fill the tank is always the hassle.

I went the cheap route on a new aluminum tank. (Of course it was Made in China. They conveniently leave that out of the ad) Not only would it not fit without hitting the cross member for the bed. The bed the filler was offset from the middle by 3" and designed for a hole in the bed floor. The center is about the worse place I could think of for a bed tank fill.
The pump was also situated behind the bed cross-member which makes the lines difficult to run. You have to notch the cross member or run the lines a the side of the tank next to the frame. Makes it really difficult to remove and replace the tank.
I would purchase a quality tank for a reputable manufacture. I believe you can get them with the pump you specify. It gets expensive but you will avoid many of the hassles I had to deal with. If you want to save money use a solution like Markdtn did and retrofit a used tank. Still have to modify it but you know that up front.
At least you don't have the initial investment of a new tank that doesn't fit.
And avoid CPP truck parts if you can.

Last edited by Accelo; 02-19-2021 at 11:33 AM.
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Old 02-16-2021, 10:52 PM   #4
Peanut74
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Re: In-cab to under-bed fuel tank conversion questions

2x Accelo advise on the tank. I bought one from Brothers and the filler neck lined up with the bed sill. Currently working on the fuel filler routing. Planning on having the fill cap in the stake bed pocket.

For my fuel line routing I used the passenger frame rail for both the supply and return lines. Had them come up in the middle of the trans tunnel.
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Old 02-17-2021, 08:56 AM   #5
MARKDTN
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Re: In-cab to under-bed fuel tank conversion questions

I actually used the fuel lines from the Blazer. It was the perfect length for a SWB. I did replace all the rubber hoses with new EFI hose while I had it out. Be careful joining lines, You need a barb so hoses don't blow off under pressure. Brass unions are not really the best choice; they are meant for low pressure. Hydraulic unions are a better choice. An easier way would be buy/borrow a Mastercool tool and make quick-connects where you need to join lines. With proper fittings you can join different line sizes if needed (like 5/16 to 3/8)
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Old 02-17-2021, 01:13 PM   #6
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Re: In-cab to under-bed fuel tank conversion questions

Quote:
Originally Posted by Xavier View Post
I've been collecting the parts to do an EFI upgrade on my '68 and was looking for some insight from other regarding fuel tank options.

I already have and plan on using a Holley Sniper EFI with a Holley in-tank Retrofit fuel pump module.

Using that setup I think I will still need a sending unit to get fuel levels, correct?

There are so many different tank options I'm not sure which would be best suited for my application. I definitely want a side filling tank.
I was in the same boat. I decided to keep it all Holley and just ordered my tank last week. I called Holley Tech with some questions about the tank and ended up ordering it straight from Holley. Check it out, Holley part #19-185. Side fill neck is #19-186.
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Old 02-17-2021, 01:49 PM   #7
67C10Step
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Re: In-cab to under-bed fuel tank conversion questions

Perfect timing on this thread and I hope I don't hijack but here is my current delima:

1967 short stepside - what are the filler options if moving tank to the rear? In bed, side, or ?

Also, if I am not going to EFI right now but might in the future is there a tank/way to accommodate that?

Thanks all, good thread on this.
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Old 02-19-2021, 11:25 AM   #8
MikeB
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Re: In-cab to under-bed fuel tank conversion questions

One of the things I want to do on my 69 C10, when I get it back this spring, is add EFI. I hate the idea of the filler being on the bed floor, but the truck was recently painted so I don't want to put a filler door in the bedside. Are their any other choices?

You can see why I don't want to mess with the bedside!

Edit: It's not ideal, but maybe my best bet is to keep the tank behind the seat. I wonder if there's pump-in-tank setup for that.???
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Last edited by MikeB; 02-19-2021 at 11:49 AM.
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Old 02-19-2021, 11:48 AM   #9
Accelo
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Re: In-cab to under-bed fuel tank conversion questions

MikeB.
Yes I get it your truck is amazing.
Another option is the fill behind the rear plate.
Like the Chevelles from the 60's and 70's. I believe they typically use the Chevelle hinged mount for the Chevelle fuel fill.
Their is also the fill that they hide behind the rear side marker light.
Installing the fill behind may require fab skill that may be beyond the average enthusiast.
One would think the fill location would have been better addressed by the aftermarket providers. Seems most go the easy route and just cut the hole in the bed. Can be dressed up some with a pop up fill/cap. In my opinion installing it in the middle of the bed is ludacrist.
I will carry nothing in the back but maybe a lawn chair/cooler. So having it there may be tolerable. I have my tank installed with the pressure and return lines but no fill yet. Even if it is installed on the very edge of the tank it's still not near the edge of the box. One of the conundrums of installing the tank in a safer but none factory location.
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Old 02-19-2021, 01:58 PM   #10
greenweenie1969
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Re: In-cab to under-bed fuel tank conversion questions

I went with the Boyd rear tank and it worker awesome. Looks good too because of the low profile fro the rear. They come set up with the sender in tank and come top fill or side fill. Great customer support too.
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Old 02-19-2021, 02:10 PM   #11
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Re: In-cab to under-bed fuel tank conversion questions

Quote:
Originally Posted by MARKDTN View Post
I put EFI on a '72 SWB for a guy about 15 years ago. Used an '86 S10 Blazer tank that had a 2.8 TBI. Swapped the pump for what I needed ('89 IROC pump). It has the correct resistance sending unit for the stock gauge. It has a side fill. On the truck I did, I notched the top of the frame for the filler neck. Somebody else put a (5th gen) stepside bed on it and made the filler on the passenger side.
I also did an S10 Blazer tank once. 20 gal, side fill, correct GM stuff, also notched the rails to drop it in. I also remember notching a bed support right over the tank.
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Old 02-19-2021, 02:43 PM   #12
67ChevroletDude
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Re: In-cab to under-bed fuel tank conversion questions

Accelo,
You forgot the option that is to route it to the corner of the bedside. I was also in the same predicament that MikeB was and opted to cut the very corner of the inside of the bed near the stake pocket to route my side fill suburban tank. That way I can still use my truck for truck things.

Last edited by 67ChevroletDude; 02-19-2021 at 03:00 PM.
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Old 02-19-2021, 05:34 PM   #13
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Re: In-cab to under-bed fuel tank conversion questions

Quote:
Originally Posted by MikeB View Post
One of the things I want to do on my 69 C10, when I get it back this spring, is add EFI. I hate the idea of the filler being on the bed floor, but the truck was recently painted so I don't want to put a filler door in the bedside. Are their any other choices?

You can see why I don't want to mess with the bedside!

Edit: It's not ideal, but maybe my best bet is to keep the tank behind the seat. I wonder if there's pump-in-tank setup for that.???
I have seen a side marker light mod and I think I have seen people leave it in the wheel well.
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Old 02-19-2021, 05:53 PM   #14
Andy4639
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Talking Re: In-cab to under-bed fuel tank conversion questions

The 68 step I was building but sold it before I finished it. It was running though. It's Rob's from 'NO LIMIT' tank and it's setup for FI if need be later on.
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Old 02-19-2021, 06:05 PM   #15
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Re: In-cab to under-bed fuel tank conversion questions

I have the in cab tank moved to the rear on my 71 4x4 fleetside. Has been there for nearly 16 years or more. Got the tank from GMCPaul, poly tank and the fuel fill is in the bed on the driver side wheel well. Works well, fills at full flow with no burp, run two vent lines up over the rear wheel wells. Get some strange looks dumping fuel in the bed at the gas station but this way it leaves the bed floor free for hauling. Had to cut a cross member to allow the bed to set down flat to the frame as it should.

Nice looking truck by the way.
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Old 02-19-2021, 06:21 PM   #16
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Re: In-cab to under-bed fuel tank conversion questions

Quote:
Originally Posted by greenweenie1969 View Post
I went with the Boyd rear tank and it worker awesome. Looks good too because of the low profile fro the rear. They come set up with the sender in tank and come top fill or side fill. Great customer support too.

I've used the Boyds welding tanks as well, they are very high quality and the customer service is great. The ones I've used have been bed fill though, that is what the customers wanted.

You could install a pump in your factory tank, but I would not recommend it, I think it would make the fuel smell unbearable in the cab due to the fuel return. You could do a surge tank setup if you wanted, that way it pulls from the in cab tank and the small surge tank houses your high pressure pump and return fuel.
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Old 02-19-2021, 08:13 PM   #17
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Re: In-cab to under-bed fuel tank conversion questions

69 camaro tank has fill that lines up with license plate
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Old 02-19-2021, 10:01 PM   #18
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Quote:
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69 camaro tank has fill that lines up with license plate
This is the Boyd tank with built in pump, I am using the hinged taillight fuel filler.
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Old 02-19-2021, 10:05 PM   #19
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This is the Boyd tank with built in pump, I am using the hinged taillight fuel filler.
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Still a long way to go...
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Old 02-19-2021, 11:00 PM   #20
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Re: In-cab to under-bed fuel tank conversion questions

I did the 69 Camaro tank rear fill behind the license plate. It's works well. A bit ackward
to fill but it doesn't spit back. The tank hangs down a bit but its well above the scrub line. I did not want to fill thru the bed or mod the bed side.
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Old 02-20-2021, 10:47 AM   #21
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Re: In-cab to under-bed fuel tank conversion questions

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I did the 69 Camaro tank rear fill behind the license plate. It's works well. A bit awkward
to fill but it doesn't spit back. The tank hangs down a bit but its well above the scrub line. I did not want to fill thru the bed or mod the bed side.
That's what I want to do with mine. As said above I really wish the aftermarket guys would realize there some of us who don't want to cut a hole in the bed, and don't have the desire or fab skills to do taillight or fender fills.

From what I've found online the biggest difference with the F Body tank is the straps don't go the same way, and as you said it does sit lower.
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Old 02-20-2021, 06:00 PM   #22
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Re: In-cab to under-bed fuel tank conversion questions

I don't recall using the stock tank straps. I went to a local metal supply shop and had them cut from stainless 16 gauge sheet metal 1" wide longer than I needed and then cut to fit. I used pieces of truck tire inner tube between the strap and the bottom of the tank. Tire shops will give bad inner tubes away.
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Old 03-29-2021, 11:51 AM   #23
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Re: In-cab to under-bed fuel tank conversion questions

Thanks for the advice, gents.

I went ahead and got a Boyd's tank, mostly because other options were on backorder until June.

Are straps a necessity with a tank? Would it be sufficient to just bolt it to the frame or are straps required in addition? I ask because Boyd doesn't supply them and their "mounting kit" is just a bar of flat stock with some threaded holes to put in the frame rail to bolt into.

Also a quick question regarding fittings. The Sniper comes with 6AN fittings whereas the Holley drop in pump has 1/4 NPT threaded holes. I already bought a 37į flare tool and plan on running some stainless supply and return lines but my question is about the fittings. Obviously I will need a fitting at either end of my hard line. I want to use flexible line at either end for the connection to the pump/efi. Do they come pre-terminated? Do I need 1/4" NPT to 6AN adapters for the pump or is that something that would be part of the flex line?

I've personally never used an AN fitting so I have no experience with them but I figure it's used in high-end builds all of the time so it must be good and I didn't own any flare tools up to this point.
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Old 03-29-2021, 04:43 PM   #24
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Re: In-cab to under-bed fuel tank conversion questions

Is your pump in the tank? I like to run SS -6 line both for the pressure side to the fuel filter regulator and the return side. I use the teflon type -6 line. I actually run SS -6 line front to back. I find it so much easier to route compared to hard lines.
You can get most any type of -6 fittings from Summit.
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Old 03-29-2021, 05:03 PM   #25
C101972
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I have in tank fuel pump, have you ever been and flared s/s lines? it can be a painful experience, especially if you donít have good quality tools. Iím just putting it out there.
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