Upgrade fuel feed line?
 

Hey guys, asking if anyone with a 500-550hp build has felt the need to upgrade to a 1/2 fuel feed line? According to the online charts you need to but I don't put much into those type of guide charts. Would love to here some real world experience. Finally Making progress on my build and putting the fuel system in next.

I haven't had any issues with mine, 500 hp 467, carter mechanical pump. I haven't done any serious racing and usually shift at 5000 rpm.

I ran a Pontiac A-Body (Convertible 3/8" fuel line) down the drivers side of the 64 GTO.
https://www.sstubes.com/?gad=1&gclid...saAs80EALw_wcB.

I ran a 3/8" 1966 Chevelle (Convertible) line down the passenger side of the 64 GTO. (same supplier).
(All factory looking using Stainless Steel pre-bent lines. I was very happy with them installation. (Posted on this in the past).
No mechanical fuel pimp installed.

The fuel tank is a Tanks,inc (dual in tank fuel pump set-up) with TWO 400 liter/Hr fuel pumps.

I use fuel from the (26 gas pump) station that offers No Ethanol gasoline.

Two switches (independent) supply the fuel to the induction system.

The system has the ability to feed a 862 HP Vortech Supercharged (T-Trim), 455 engine.

Tom V.

1/2" fuel pump line is a smart move. Upgrade the pick-up line in the tank too.

My motor Dyno'd at 430 hp (many here think it should have been more like 500). I have a 3/8 factory line and with a BOP Carter style 120 gph pump it was starving bad. It would suck the bowl dry by about 4000-4500 rpm. I went to a RobbMc 550 hp pump and there was a dramatic improvement with no obvious starvation but I think it would still benefit from a 1/2 inch line. I'm planning on doing that next spring along with a baffled tank from Tanks Inc.

If your going racing and you get decent 60’ft times, keep this in mind.
you will find that for every foot of fuel line running from the rear at the tank to the front of the car that fuel pressure will drop .3 psi per ft due to G forces.

This is all really good info. Thanks guys. Sounds like I'll up to a 1/2 line and pickup. I'll be running a robbmc pump and I'll just order on of his pickups too. Still in the early stages but shooting for low 500hp range.

I'd go 1/2" feed and return with a regulator and a fuel pressure guage you can read while driving.

A true 500 hp motor would have about a .5 BSFC number showing up on a dyno print out, this converts to a need of 250 GPH.

This means with certainty that a 120 GPH pump will not support anywhere near 500 hp.

Myself & many others have used the common carter/edelbrock mech pumps that are rated at ~120GPH that support 500 hp engines. My 467 engine dyno'd on a "strict" crank dyno at ~520hp using an edelbrock mech pump, did numerous pulls and didnt have any issues but not sure what fuel ratios were since it wasnt a real dyno tuning session with all sensors hooked up, just some pulls on break in to verify no leaks, all parts like Q-jet carb & HEI dist were set up by cliff & suntuned & just bolted on with no real tuning.

The edelbrock pump says its rated "up to" 600 hp and was proven to support 500+ on a dyno with no problems, it did fine on the street too, however at the dragstrip it would only do low 12s with pretty bad starvation issues, using 1/2" pickup & lines to pump & pump to carb. Changed to a robbmc 1100 mech pump but was dialed down to 7psi with no regulator, with no other changes besides some skinny front tires the car has went 11.2-11.3 at 119-123mph... but still have occasional starvation on good runs.

Just wanted to give an example of a 120GPH pump supporting over 500hp when sitting still on a dyno, add in G forces from good launch & into the 11's and most cars will have problems.

For the OP's question, 1/2" lines arent usually needed for street use but a good pump like robbmc is a good idea, if doing any drag racing you may want to upgrade the lines.

I think the Q jet if a big factor in this equation-one needle and seat one small bowl.
My personal experience in my 78 TA Stock motor added a 228@ 0.050 cam -stock pump and 3/8 line ran out of gas top fo second. Added a small AC Delco electric pusher.
Added a real 430 hp 455 through mufflers on dyno with a Qjet-fell on it's face. Tried every mechanical pump-no help. Added a dead headed Mallory 140. Solved -until I uncorked the headers probably adding another 30 hp. Issues again. Added -8 from Mallory to carb and dropped the mechanical pump and it supports me into the 11s with a Qjet and now 10s with a Holley with still a factory 3.8 pickup-no sock.

Qjet may be a factor, just wanted to post a real world experience with a 120gph mech pump supporting over 500hp when it was said these pumps will not support "anywhere near" 500hp.

Back in the early to mid 90s i had a mild 455 (462) in a 78 t/a with a holley dbl pump mech secondary carb, milled .030 6x4 heads, 280 magnum cam, headers, 2.5" exhaust, th400, 3.90 gears. that car ran stock lines & pickup with a stock large canister AC mech pump... it was never dyno'd or went to the drag strip but on the street it would beat mid 12 sec cars that would come cruise our avenue with time slips in hand, i would easily beat them on stop light to stop light short runs and when we went to a divided highway section we had marked for 1/4 mile, it would beat them the entire run... that was my only verification for how fast the car was, im sure it would run mid 12s or better with good tires. I would guess at least 425hp on that motor that ran great on the street with stock pump & lines. The 120gph pumps can & do support 500hp engines.

Sorry, I forgot to convert my number I posted, so yes 120GPH will support 500 Hp.

My buddy dynoed the 400-495 we assembled with stock intake q jet and stock pump and line from carb to pump it made 541hp at 5500rpm it was just starting to go lean over 5500 but not damaging lean. I wish we could have tried a mcrobb at that time but didn’t have one yet. The stock pump got a stock body 69 gto with stock everything else but drag radials to 11.80’s. All cars are not the same even with the same size lines my 80 t/a with stock line needed an electric pump by tank not to nose over in third gear a 110 Mallory fixed that problem that car only went low 12’s. The purestock Firebird my buddy runs goes 113-115mph with all stock parts being used.

Completely wrong. Check out the Tanks, Inc offerings and tech. I have their 340lph pump which converts to 90gph with zero starvation. They say their 250lph pump will support 500+ hp

My car years ago with a 550hp engine? picked up almost 2 mph just by swapping from stock pickup and 3/8 line to all 8an lines and half inch pickup. At that time it was running high 11's.

Like has been mentioned, most will get away with smaller 3/8 line and never know there is a fuel delivery problem on the street, as most here don't bother or even worry about track performance, but will quickly find out there is ET and MPH to be found in that area as soon as they hit the track.

In nearly every scenario when I've been involved with a decent running street car, they've benefitted from 1/2" line and a good pump feeding it. Surprising the amount of people that spend a bunch of money on engines, worry about the HP they make, then skimp on the fuel delivery system. We've all done that, myself included. I quickly found decades ago as power level keeps increasing the fuel delivery becomes a key player. These days right off the bat I just spend the money and shoot for an in tank pump and 1/2" lines and call it done so I never have to revisit it again as the car evolves further.

A LOT OF TRUTH AND EXPERIENCE IN THAT POST.

I KNOW TANKS, OFFERS A "TRAP DOOR" YOU CAN ADD TO YOUR FUEL TANK (to service a failed fuel pump) BUT I JUST SET UP
MY FUEL SYSTEM WITH A PRIME FUEL PUMP AND A BACK-UP FUEL PUMP ON THE FUEL PUMPS FUEL PUMP MOUNTING COVER.

Food for thought there people.

Tom V.

You can support big HP with pretty much "stock" fuel systems and simply a mechanical pump upgrade right up untl the moment you take steps to make the car hook really hard and pin you in the seat on the launch

At this point sucking fuel some 14' or so from a stock in tank sump with stock lines will not longer make the grade.

What muddies the water here is that some folks post they they get away with it run on down into the 11's and some even on into the 10's without any further upgrades when most folks trying to do the same thing can't get out of the 13's.

I went thru the entire evolution with my car when I started installing bigger engines, more gear, converter and good tires. At the end of all the efforts to keep the carb full on hard runs I ended up sumping the tank and installing a 140gph pump behind the tank and 8AN lines/fittings everywhere.

That move INSTANTLY solved any and all fuel delivery issues and the car picked up a solid 2-3 tenths and at least 3-4 mph. That was just on the first outing. I made a few more changes and went on to run much quicker and never again experienced any fuel delivery issues whatsoever.

Since technology has improved considerably if I were doing it over again I'd go right to an in-tank system and "push" all the fuel and run a full return back to the tank. Then, as mentioned someplace above I could continue to make changes to make more power and go faster at the track without having to re-visit fuel delivery issues.......FWIW.......

I was taught when you want to run 12's you need to upgrade to 1/2 inch fuel line....that was forty years ago and pump technology has changed a bunch but that rule never failed me.

At 500 HP I'd think 1/2 would be helpful. I ran 1/2 with a hidden baffled pick up drawing from the front of the tank with a Holley blue pump for years. That worked fine for low ten second ET's but once we upgraded to nine second power I added a sump and better fuel pump to make things happy.

Is the situation different for EFI? With an in-tank EFI pump is the goal to maintain the fuel pressure required at the throttle body and sizing the fuel line to meet said PSI?