Holley Sniper and Gas Tank Swap

Bextreme04 · Sep 9, 2022

Also... since this is a suburban, shouldn't you have no clearance issues even with the 40 gallon tank? The 31 gallon blazer tank easily clears my 14BFF on my K25 pickup, but the 40 gallon would be close.

SquareRoot · Sep 9, 2022

Vbb199 said:
While the community appreciates and loves all opinions, respectfully, your failed holley installation doesn't make ALL holley efi junk.

-signed the entire high performance community that makes more than the 450hp the PF4 supports

Installation was per instructions. The repeated dead ecu for no reason was the last straw. Crappy Holley tech line just had me uninstall and send it back. Twice! I needed my truck to run without fear of being stranded. And each time it was a "firmware" issue. I'm not taking my family for a ride in the desert and having to worry about a good internet reception so I can download and reinstall firmware to get me home.
There are other issues but they're minor in comparison. For $1000 I expected better.

Vbb199 · Sep 9, 2022

Bextreme04 said:
I thought the sniper had its own internal regulator....

I've heard mixed reviews on the integrated corvette filter/regulator. I ended up just going with an external adjustable regulator on the return line so that I could vacuum reference it to the manifold and maintain a consistent fuel flow. Makes it a bit easier to tune the EFI when you don't have good injector data.

I'm currently pushing walbro 450 pressure thru my sniper regulator, if there's any doubt, you should look up the pressures a 450 operates at.

The holley rep I spoke to on the telephone said it'll handle I'm thinking 120 psi max internally regulated.

Bextreme04 · Sep 9, 2022

Vbb199 said:
I'm currently pushing walbro 450 pressure thru my sniper regulator, if there's any doubt, you should look up the pressures a 450 operates at.

The holley rep I spoke to on the telephone said it'll handle I'm thinking 120 psi max internally regulated.

My second paragraph there is referencing LS swap and OEM type fuel injections. I probably should have specified that in my original post. The reason I was saying that is I had never seen anyone use a separate regulator on a holley unless they didn't want to run a return line all the way to the motor. It seems to me you are just asking for more trouble and expense by doing that though.

A stock EP381 in an 87 EFI tank and stock 87 sending unit is simple and easy to get replacement parts for if anything ever fails. You can get the adapters for dirt cheap to go from the TBI fuel lines to -6 AN and then run AN lines all the way up to the Holley and back to the tank for feed/return. No extra regulators or filters necessary. For extra feel good, put an EFI filter somewhere in between there on the frame rail for easy access to clean/change it out and prevent the EFI injectors from getting clogged if the pump frags.

Frankenchevy · Sep 9, 2022

I’m confused why folks think the sniper needs an external relay? Mine ran fine with 12v from the fuse panel. It needs to supply a clean 12v when in “Run” and “Start” with no hiccups in between. I did install a new ignition switch because when I toned out the the fuse contact it was a bit ‘scratchy’ when I cycled the key. New switch, solid tone.

Though, you can definitely use a simple switch with 12v directly from the battery or relay if you’d like. And as VBB said, the blue 12v wire for the fuel pump is ample for most setups.

Regarding the PF4 only supporting 450hp, I believe if you use the correct regulator and injectors it will support more. The throttle body itself should be high enough CFM to get a fair bit past 450. I made the mistake of ordering the regulator for 400hp and up, but that will turn out to not be a mistake when I install a 383.

consti2tion · Sep 10, 2022

Bextreme04 said:
I thought the sniper had its own internal regulator....

I've heard mixed reviews on the integrated corvette filter/regulator. I ended up just going with an external adjustable regulator on the return line so that I could vacuum reference it to the manifold and maintain a consistent fuel flow. Makes it a bit easier to tune the EFI when you don't have good injector data.

Bextreme04 said:
Also... since this is a suburban, shouldn't you have no clearance issues even with the 40 gallon tank? The 31 gallon blazer tank easily clears my 14BFF on my K25 pickup, but the 40 gallon would be close.

I have read mixed reviews on the integrated filter/regulator too but I think it's dependent on which filter people get. The Wix filter is supposed to function great, so that's the one I went with. If it ends up being a crapshoot I'll just put a return line on it back to the tank.

As far as the tank goes, the OP has a K series truck, not a Suburban.

Bextreme04 · Sep 12, 2022

consti2tion said:
As far as the tank goes, the OP has a K series truck, not a Suburban.

Well that makes it even more weird. My 31 gallon blazer tank has tons of clearance on my K25 pickup

chuckler3 · Sep 14, 2022

Frankenchevy said:
I’m confused why folks think the sniper needs an external relay? Mine ran fine with 12v from the fuse panel. It needs to supply a clean 12v when in “Run” and “Start” with no hiccups in between. I did install a new ignition switch because when I toned out the the fuse contact it was a bit ‘scratchy’ when I cycled the key. New switch, solid tone.

Though, you can definitely use a simple switch with 12v directly from the battery or relay if you’d like. And as VBB said, the blue 12v wire for the fuel pump is ample for most setups.

Regarding the PF4 only supporting 450hp, I believe if you use the correct regulator and injectors it will support more. The throttle body itself should be high enough CFM to get a fair bit past 450. I made the mistake of ordering the regulator for 400hp and up, but that will turn out to not be a mistake when I install a 383.

I've got some of the messiest wiring I've ever seen in this thing.. Pulling clean 12v from the battery via a relay is a cheap/easy insurance against the previous 40 years worth of owners and their strangely colored wires.

chuckler3 · Sep 14, 2022

consti2tion said:
I spent a lot of time trying to get the wire looms to look clean under the hood, a lot of moving components around etc. The hyperspark added a some more frustration on the wire routing and placement though so it shouldn't be as bad for you.

I considered just buying the fuel lines from "linestogo.com" for the FI suburban but decided to just go another route.

Fuel filler hose is surprisingly expensive at local autoparts stores but not too bad on amazon. I need to figure out a better system for routing mine on a completely different project and it is hard to figure out what will actually flow correctly and vent properly when filling so it won't "burp" or click the pump off constantly, I think that will be the most difficult task. I have a 1971 Dodge Sweptline with a D250 chassis swap and currently I just have the fuel filler in the wheel well, if you aren't able to get it routed easily you could poke it out in the wheel well and build some sort of cover/door over it.

That "filler in the wheel well" is an ignorantly brilliant idea and will be hard not to consider if I can't route to the stock placement. Thinking standard hole with a cheap filler cap interface (read: generic) and then a flap of 1/4" rubber floor mat/mud flap to hide it.

As of now, my filler neck on the tank is just at the lower body line while the door on the fender is at/above the same body line. Time will tell if the degree of fall is enough to fill 32 gallons in a timely fashion.

Just ordered a bed bolt kit and patch panels from LMC for the bed floor, and some square hole washers from Mcmaster to resolve my rounded out carriage bolt holes... And just realized I completely forgot to pick up a few of those replacement cross members that weld to the buttom of the bed.. great.

my $75 harbor fright flux welder is gonna get a workout.

Frankenchevy · Sep 14, 2022

chuckler3 said:
I've got some of the messiest wiring I've ever seen in this thing.. Pulling clean 12v from the battery via a relay is a cheap/easy insurance against the previous 40 years worth of owners and their strangely colored wires.

I hear ya. There’s no time like now to throw a painless harness in, if the original is hacked up.

SquareRoot · Sep 14, 2022

Vbb199 said:
I'm currently pushing walbro 450 pressure thru my sniper regulator, if there's any doubt, you should look up the pressures a 450 operates at.

The holley rep I spoke to on the telephone said it'll handle I'm thinking 120 psi max internally regulated.

consti2tion · Sep 15, 2022

@chuckler3 I'll try to get some measurements of how high the filler is on the Suburban from the factory, there isn't a ton of fall from the filler to the tank though so you should be fine as long as you have it vented properly.

chuckler3 · Sep 15, 2022

Frankenchevy said:
I hear ya. There’s no time like now to throw a painless harness in, if the original is hacked up.

That was a hard decision to make, not replacing the wiring harness. In the end, I essentially said that if the truck had a better body on it (it doesn't), I'd go that route. I've focused on mechanical resilience for now. If the time comes to shine the turd's body and/or replace panels, it'd require removing the cab/bed again and the electrical would get replaced at that time.

chuckler3 · Sep 15, 2022

consti2tion said:
@chuckler3 I'll try to get some measurements of how high the filler is on the Suburban from the factory, there isn't a ton of fall from the filler to the tank though so you should be fine as long as you have it vented properly.

I'm thinking the 3-5" fall over a 3' run from stock filler location to the new tank inlet should be enough. Tank has provision for the 1/2"(?) breather hose that went to the stock filler location. Technically I'll be running a big hose and a small one all the way to the stock location if I can pull that off. Also has a 3/8" line with a roll-over breather/vent as well. Should be good on the back-pressure front.

I'll always take reference pictures.. Hard to function without them sometimes.

consti2tion · Sep 17, 2022

chuckler3 said:
I'm thinking the 3-5" fall over a 3' run from stock filler location to the new tank inlet should be enough. Tank has provision for the 1/2"(?) breather hose that went to the stock filler location. Technically I'll be running a big hose and a small one all the way to the stock location if I can pull that off. Also has a 3/8" line with a roll-over breather/vent as well. Should be good on the back-pressure front.

I'll always take reference pictures.. Hard to function without them sometimes.

Sorry I haven't gotten a chance to snap a picture. The hose from the breather for the filler that goes to the tank on mine was a 5/8" hose. That should be more than enough fall to achieve a proper fill.

Holley Sniper and Gas Tank Swap

Bextreme04

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