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?

You’ll be borderline on the street. Upgrade if you hit the track. My old 470 ish hp 455 did well on the street. At the track, it would pop through the air cleaner just before the line at the top end. Pulled the plugs. All white like a bed sheet.

I don't have a bunch of experience with EFI at the track other than racing LS engines back in the 90's and early 2000's. All those vehicles had smallish factory fuel lines, but they also pump 58 psi fuel pressure too. I ran them into the 11's and near 120 mph without issue but I did upgrade the factory in tank pumps. Others were going even faster with them back then.

Pressure is one thing, volume is another, I'm sure you're aware.

Whether it matters or not, when I'm doing a moderately high HP EFI build, I just run the 1/2" lines to and from and be done with it. One reason is because I'm typically replacing fuel lines on a build anyway, so I just upgrade to 1/2", the cost is the same.

Ironically both of our current EFI cars (one running 10's and the other 11's) already had 1/2" lines and in tank pumps when they had carbs, so all of that was left in place when the switch to EFI was made.

Thats a very good point. And when put like that I guess it's a no brainer to upgrade with all the money going everywhere else to.make power. Thank you.

Need to figure in 6 lbs/gal, so 41.6 gph

Sent from my SM-S901U using Tapatalk

Paul,
What fuel setup do you have on that pretty light blue TA of yours?

Send Caster1 a DM and ask him about his setup, it has a 1/2 pickup and a few other mods. Its pretty sick.

That's the car I was talking about. I always wanted that car to look "stock". For years I ran two Holley blue pumps. One through the factory 3/8 line for the nitrous and one for the motor side. I added a peice of .500 tubing that entered the front of the tank but ran to the rear. That set up worked well when the car ran bottom 11's and low tens on spray. When we upped the power it became inconsistant and the pressure gauge moved around more than I liked. No matter what I tried I couldn't get it to work to my satisfaction so I ended up installing a new tank with a sump.... Now I need to build another car to use the old tank :D

Pretty simple to make them look stock with a little thought and time.

I use the Tanks Inc tanks with the pump in the tank. No sumps hanging down. I run the 1/2" line, sometimes using stainless pre bent stuff from places like Inline or Right Stuff, which gives the appearance of stock if anyone cared to crawl under the car.

I then keep the stock mechanical pump in place if it's visible (like a Chevrolet) and keep the stock steel lines running to the carb or EFI, although it's all dummy stuff with the line soldered shut.

The 1/2" line I hide in the back where it can't be seen.

Look under the car or open the hood and it looks like a typical street car with a mechanical pump but it actually has a fuel system that'll support 1000+ HP depending on which pump I put in the tank :D

Agree..... None of that was an option in mid 90's when I modified my fuel tank. Billet fuel pumps were just coming out. Most folks used the BG pumps and they didn't recommend them for any type of street use. We tried a Mallory 250 three different times and it never worked. Mallory tried three stabs at fixing it and it still failed.

Understand, I did a lot of the same things back then, that's all we had. Can't tell you how many times I had to rebuild that damn mallory pump lol. They tend to start complaining after a while of continuous street use. Always had to replace brushes in the things.

They make it so easy these days with these fuel systems, it's like modern car stuff. Problem is.....none of it's cheap.

Ok so I got a robbmc 1/2" pickup and inline tube 1/2" fuel line on the way. Now my question is do I need to get a 1/2" carb feed line from the pump or will the robbmc pump supply suffecient pressure with a 3/8" line.

Ive done 3/8 from the pump to carb or the regulator to carb to make things look stock and works fine. 1/2" is always better but the most important thing with a mechanical pump is having the larger feed line on the suction side because they aren't good at sucking, that's a long distance and making it as easy as you can on the pump with larger line helps that scenario.

Agreed the bigger pump to carb line isnt always required, but, if you have a Q-jet & dont care about an original looking/size line, using a 1/2" or -8 AN line will provide a little more fuel from pump to carb if that matters. Its easy to run a -8 line from the robbmc pump outlet to the carb using one of cliffs -8 AN fitting & high flow marine filter.

This is very timely for me, very. My RobbMC came this week and I took out the old pump last night. I've been making a plan for needed fittings and was about to head out to the garage and check about the routing to the carb. The 3/8 outlet comes out the opposite side of the pump's inlet so it looks like I'll be using a 90 degree fitting to come out and straight up. Summit has a line (PTFE) by Fragola with this fitting feature already as assembly. I was going to determine if the line would fit through the factory routing between power steering pump bracket and timing chain cover. I, however, don't know the 3/8 line O.D. nor the bend radii of the line to see if this is possible. This obviously has everything to do with picking the correct line length as well. If I can't snake a 3/8 line through the original routing and have to find a different path I will go with a 1/2 line but where does it run? It must come up around the outside of the alternator and over or behind it over the valve cover? Im not concerned about original routing but am very cautious of moving parts (fan, pulleys, belts, alternator and pump adjustment) and electrical and headers....You already know that....Does anyone have a hint or even a picture?

I have an older version of the robbmc 1100 pump, not sure if the inlet/outlets are the same as newer models or the 550, but I used a summit or fragola brand curved 90 AN fitting on the outlet then ran the -8 braided hose up behind the p/s pump & alternator basically where the stock metal 3/8 line runs, -8 line is about 1/2" OD so its a lot bigger than 3/8 line, it slides through that area easily and is nowhere near moving parts or belts, its rigid ennough that it stays in place... i even added a small regulator to it that sits near the T-stat housing freely suspended with no bracket. i can get some pics of how its routed but its really pretty basic.

Dont forget the robbmc pump is clockable so you can adjust where the inlet/outlets are somewhat.

Thank you 78w72, pictures not needed, I see that a 1/2" OD line will fit through there fine and it sounds like it will be able to take the slight curves necessary to hook up and not kink or anything like that. Do you have an in-line filter along with the regulator too? I've usually used in-lines as it seems the in-housing filters (short/long) are so small but I see that Cliff sells pleated filters so they must be able to do the job. It would be a cleaner instl without.

The clockability is a cool feature. I'm really impressed with the quality and heft of the unit.

Just an FYI, the pump I took out had the outlet (bottom) on the same side of the pump as the inlet (1969 428) and I also looked at the pump on the 1969 400 in my other car and the outlet is on the opposite side of the pump. I would not claim either configuration is original or correct or whatever but the lines for both go up between timing chain cover/pump bracket/head.

thank you for your help

Yes a 1/2" line will fit like the factory routing, even a custom made steel 1/2" line should fit but the braided line makes its an almost straight run under the p/s pump & under/behind the alt with nothing even close to kinking... i did put a slit piece of heater hose over the line where it barely rests against the alt bracket just to be safe but no sign of any issues after 7-8 years. Can also put a section of heat shield on the line if thats a concern but ive never had any heat related issues with fuel.

I have filters, one bigger tanksinc right after the tank then just use the marine screen type right before the carb, cliffs AN fitting uses the high flow marine screen type, im sure you can use the factory pleated paper type too but the marine filter is supposed to flow better. I have checked both filters a couple times after years of use and the carb one is always spotless and so is the bigger one but it has a brass element so harder to see if there are any small specs in it, looks totally clean to me, i do have a new tank so no debris to get churned up. I dont have or feel the need for any other inline filters.

Heres a pic just to show the carb AN fitting & how the line is ran, i have since shortened the line a bit & now run a regulator for when I want to dial the 1100 pump up to a higher psi for track use but a regulator shouldnt be needed for most carbs with the 550 pump since its set at ~7psi.

I've done 1/2" steel line from pump to carb on some installs. It fits and works. Just a little tedious and time consuming but it all is really.

Thank you 78w72 and Formulajones. My plan is in place and putting the parts list together.