This is why I like chat gpt, some may knock on it but I like it. The only thing I wouldn't trust is letting it tune for me.---
Basic layout (fuel flow order) Factory tank → factory in-tank pump (lift) → surge tank → external high-HP pump → fuel rails → regulator → surge tank → surge tank overflow → factory tank That loop is what keeps the high-pressure pump fed no matter what the fuel level or G-loads are.---
Parts you’ll need1–2 liter surge tank (with 4 ports minimum)Factory in-tank pump (can stay stock for lift duty)External pump Post-pump fuel filter (10 micron EFI)Return-style fuel pressure regulator-6AN minimum (-8AN recommended for 700+ hp)Relay + fused power for external pump---Step-by-step install1. Mount the surge tankMount it close to the rear of the car, lower than the trunk floor if possibleTrunk, spare tire well, or under the car near the tankMust be secure and isolated (rubber mounts help noise)---
2. Use the factory pump as a lift pumpLeave the factory pump and pickup unchangedFactory feed line becomes your lift lineRoute that line to the bottom inlet of the surge tankLift pump only needs to supply volume, not pressure> The factory pump will keep the surge tank full even when the main tank uncovers under hard launches or cornering.---
3. Surge tank overflow / return to main tankThe surge tank will have an overflow port at the topRun this line back to the factory fuel tank returnThis keeps the surge tank from overfilling and bleeds off excess fuel---
4. Feed the external high-HP pumpRun a line from the bottom outlet of the surge tankInto the external pump inletKeep this line short and straightGravity-fed if possible (pump below surge tank level)---5. External pump to enginePump outlet → 10 micron filter → fuel railsUse -8AN if boosted or high horsepowerKeep filters AFTER the pump, not before---6. Regulator return to surge tankFuel pressure regulator return goes back to the surge tank, not the main tankThis keeps hot, aerated fuel out of the factory tankConnect this to a mid-level or designated return port on the surge tank---
7. Electrical (important)External pump must haveedicated relay10–12ga power wireSolid chassis groundTrigger the relay using:ECU fuel pump output orFactory fuel pump trigger (common on F-bodies)---
Line sizing recommendationsLift pump feed to surge: -6ANSurge → external pump: -8ANPump → rails: -8ANReturns: -6AN---Common mistakes to avoid❌ Returning regulator fuel to the main tank❌ Mounting surge tank higher than the external pump❌ Using the external pump as a lift pump❌ Not venting the surge tank properly❌ Undersized wiring on the external pump---
Why this works so wellFactory pump stays happy and coolExternal pump never sees airFuel pressure stays rock solid on launches, corners, and low fuelSupports big power without tank mods

 

Then the only question is how much power could the surge tank support and might I only need two 450 pumps or would I still need three.
I could mount it down in the t-top well which would be perfect.
I'm looking at roughly the same cost for any of these setups really, $700 for in tank pumps, $600 for big external pump (if the bung could be used in the stock tank), $600 for a Radium tank.

 

how much power are you looking to make? I have 2 525s in my truck but im only probably 800 wheel.
I dont think the surge tank supports the power, the factory pump keeps it full and your external pump size would be the supply .

 

I'd like to have enough to comfortably cover 1,000whp on E85.

 

I asked it about 1000 wheel and this is what I got back, but ive seen many guys with high horsepower cars setup similar to this.

1. Factory fuel tank (factory in-tank pump used as lift pump only) 2. Factory tank → surge tank: -6AN lift line 3. Surge tank: 2.0L minimum, bottom feed / mid return / top overflow 4. Surge tank → external high-HP pump: -8AN (gravity fed) 5. External pump → post-pump filter: -8AN minimum (-10AN preferred) 6. Post-pump filter → fuel rails: -8AN minimum (-10AN preferred) 7. Fuel rails → fuel pressure regulator: -8AN 8. Regulator return → surge tank: -8AN 9. Surge tank overflow / vent → factory tank: -6AN That’s the correct front-to-back fuel layout for 1000 whp turbo on E85.

 

The only variance I get is how much twin 450's can support, I've got some say it'll support 1,000whp and some say it won't including my tuner.
This is the current in tank setup with the 450's going out through the factory hat outlet which I believe is 3/8" with an -08AN adapter with -08AN up to the passenger fuel rail. My thought was to maybe drill the hat and install a -08AN bulkhead to increase the flow if it would help get more out of the 450's.
There is a good chance I'm over thinking this lol.

 

This is my setup on my truck, before I had dual 340's on my truck but i did exactly what your talking about. I put an 8an bulkhead in the top of the hat. I also put my flex fuel sensor in the return, I know alot of people say dont, but my thought process was I didnt want anything restricting me on the feed size. I pushed those pumps and fic 80's to 750 wheel and I was at 90%. I knew i planned to push the new motor a little further so I changed the pumps to the Huron speed hat with 525's and put the bosch 210 injectors at the same time so im not sure if it were the injectors or pumps at 90% but I know now I have plenty fuel. Now my turbo would be contributing factor because that next gen 2.5 78/75 isnt making it too 1000 wheel. I honestly thing fueling wise I could get there though. Everyone always says different numbers on the pumps, I think it all depends on how good your tuner is as well, ive seen some tuners squeeze every drop out a fuel system and then some that will stop at 90%.

 

I'm planning on doing this to my Firebird this winter. 8AN bulkhead fitting, but with a 450 as my main pump and a 525 as my secondary hooked up to a Kenne Bell Boost-a-Pump. I have twin 340s right now and they just can't keep up. Unfortunately for me, I'm going to have to fabricate everything because no one makes a drop in setup for a '98 tank.

 

I think you could swap to a 99-02 fuel tank?

 

Yes you can easily enough just need to wire it up a bit differently to make everything work. I'm planning on doing this with my 91 Z28 so I can drop in dual 525's

 

I didn't know you could do this on the 3rd gen too lol.

 

Yep and of course I came across that right after I pulled my new metal tank out of the box. Hawks sells the tanks for like $300 not too bad and Huron speed makes a hangar they will take dual 450 or 525 pumps

 

I emailed Huron yesterday and they're twin 525 hanger will support 1000whp on E85, they said no way with 450's which is good to know.
They also haven't had any issues with the 525's failing prematurely that they're aware of, now to be fair guys may not be reaching back out to them if a pump fails, I know I probably wouldn't.

 

That's really good to know that they haven't had failures of 525's that they know about anyway

 

I have the Huron speed dual 525 pumps in my truck. I put them in the truck June of 2024. Keep in mind I dont daily my truck but i do take it out quite often and they havent given me problems. The only issue i had with them was a power supply problem and that was my fault, one of my power wires were loose and they were losing signal. Primary pump runs like factory and i have the second pump wired in to holley with tps activation. The pictures I posted are the Huron kit.

 

Nic D has seen them fail which is the only reason I'm hesitant about it, wondering if maybe the ones he saw were Chinese knockoffs or if they were used in a return less system because that seems to be a no-no as well.
I'm reading lots about melted wiring/relays and high amp draws which makes me wonder about under sized wiring and low voltage or is it just the pump....
*EDIT* So I emailed Walbro and asked if the 525 can be run constant duty or if it must be PWM controlled and they said it can be run either way, that the 525 is PWM capable whereas their other pumps like the 450's are not.

 

I think a 525 at full tilt is something like 29 amps. So it's a power hog for sure. You'll definitely need to have the wiring top notch even go overkill with it just to be certain

 

That's exactly the same type of thing I did on my Z06 with the MoTeC C127. Mine came from Mako Motorsport and they have all sorts of those types of things for many different vehicles and displays.

 

Aww man I wish I knew about this before I installed an Autometer cluster in my 91 Z28. I would've much preferred to have a Holley 12.3" pro dash in the car

 

Yeah that's at 160psi which I'd never get there, figure 45 base plus 25 lbs. of boost max gets me 70 psi at 20 amps which 30 amps requires 12-10-gauge wire so if anything, I'd use 10 gauge just for insurance.
The pumps would have full 13.5+ volts so no worries there.