Fuel/brakes/ clutch steel braided lines

[NORTHDATSUN510]

First I will start with the fuel lines. The fuel cell I am using has a 10an fitting for the feed and the return lines, my fuel pump ( walbro 255 fuel pump) has a 3an in and out. And I am not sure what the inlet on the fuel rail is ( S14 SR20 DET) nor the return line size from the fuel rail. Is going from a 10an to 3an to large of a jump? will this provide enough flow? Second the brake lines, I am using 4an sized line is this too big? and and would 4an or 3an hose end fitting fit directly into the clutch and brake master cylinder? third for the clutch what size hose end should I be looking to purchase for the S14 SR20 Transmission?

 

Any and all help will be greatly appreciated!

Thanks,

 

Ben

[datsunaholic]

3AN to 10AN is a huge difference. 3AN is 3/16ths and 10AN is 5/8ths. More than twice the size.

 

10AN fuel fittings are huge. We use 10AN to feed a 1710ci V12 at 400GPH.

 

3AN is apparently common for brakes... I didn't even know 3AN was a common size, as the SMALLEST I've ever used was 4AN. But this is aircraft-engine stuff. We use 4AN for gauge feeds, water bleeds, fuel vents, and individual bearing lube lines.

 

As for fitting a STOCK master cylinder, I seriously doubt it. The stock brake and clutch hydraulics use metric flare fittings. You'll need an adapter from the 10mm inverted flare to 3/16ths standard. You'll need that at both masters and at the clutch slave, all 4 brakes, and all the splitter fittings if you're replacing the hard lines entirely. I don't know about the SR but 10mm is pretty standard for clutch slaves.

 

I'd use 3AN for the hydraulics and 4AN for the fuel, but I don't know your intentions here.

[Dime Dave]

First -3 is the largest you should use on brake lines and you should use hard lines for all the OE hardline locations to keep a decent pedal feel. Reason, while the -3 flexes less that the OE rubber/cloth hoses, it still flexes. I heard of a Datsun race team that had a sponsorship from a steel braid hose shop. They replaced every inch of brake line with -3. After hours of bleading and getting every bubbble out ofthe car they still couldn't get a firm pedal. They changed to hardlines except for just what was needed for flex at the suspension points and everything was good again.

 

My 1200 racecar has a Tilton clutch. When I changed to a different transmission, it put the clutch slave on the opposite side. I didn't have time to hard plumb it so I extended the -4 line to reach the slave. The pedal felt good but it wouldn't fully disengage the clutch even with the pedal on the floor. When you looked at the line during clutch opperation you could actually see it swell when pushing in the clutch pedal. I changed the line to 3/16" hard line with about 8" of -3 and the clutch disengaged at 1/3 the distance to the floor. Problem solved.

 

In the world of formula cars they use -2 line on the brakes. The length of flex is allot longer and the -2 has so little swell that the longer lines are acceptable iwth -2.

 

For fuel, -6 is plenty for most auto applications. -8 in rare cases but -10 is overkill.

 

I hope this helps.

[NORTHDATSUN510]

This has all helped greatly especially the hard line business honestly had no clue...needless to say I will be returning some steel braided lines haha. But for the fuel line there is zero option the output and input on the fuel cell I have is -10an and the fuel pump inlet and outlet is 10mm.. I do not wish to run 6' of -10an line...just from the the tank to a set of reducers to the fuel pump( by the looks and sounds of it I will be needing quite a few) and then the rest would be run at -4an to the motor and then on the return line would be -4an from the motor to a set of reduces to take it back up to -10an to the fuel cell. With the brake and clutch lines 3/16 hard line to -3an is the way to go then? Again thanks so much just wish I would have asked this before I bought $400 worth of steel braided line haha.

 

Thanks,

 

Ben

[datsunaholic]

I just hope your fuel pump is up to pulling fuel up a line that big. It's like trying to use a garden hose as a straw, with a fitting that big. 10AN is enough to feed a midsized jet turbine engine.

 

You won't need a bunch of reducers, they do make them to go from those 2 sizes in one go.

[NORTHDATSUN510]

Nice my search for this fitting starts!!

[Dime Dave]

Ben,

First, does the pump have removable fittings so you can upsize to a larger line?

 

A Walbro EFI pump should be pulling from a swirl pot not directly from the fuel cell so the pump gets constant fuel supply. EFI pumps use fuel for cooling. If the fuel level drops and the pickup sucks air, the momentary starvation can accelerate EFI fuel pump failure. The longer the starvation the quicker the pump will fail.

 

A swirl pot is basically a small fuel tank. It is fed by a low pressure pump (AKA lift pump) that pulls fuel out of the fuel cell and into the swirl pot. The high pressure pump then draws fuel off the very bottom of the swirl pot to feed the engine. The return line from the fuel injector rail is fed back into the swirl pot and an "over flow" line is run from the top of the swirl pot back to the fuel cell. The swirl pot is a sealed tank with the only vent being the overflow back to the cell. This line if located at the highest point of the swirl pot will evacuate all the air from the swirl pot.

 

The lift pump (or any fuel pump) that draws fuel should be mounted as low in the chassis as possible. If it can be below the pick-up height it is even better. The lower the better as it requires less effort to draw fuel from the tank. Some low pressure pumps have extremely poor suction and can lose prime if mounted too high above the cell.

[hosestop@msn.com]

Hey I stock # 10 pipe to # 6 an in an aeroquip steel fitting also may have in 90 degree (one fiting ), sometimes I use a Mercedes fuel pump which has #10 in and I make out either 3/8 #6 or even 5/16 which is stock s-13-s15 size seems to work fine for most street applications ,hey Fontucky just come by bring zoro .

[NORTHDATSUN510]

Dave you were talking about swirl pots? I have found several online...in 4 liters and 2 liters what should i be looking at? also what do you suggest for a lift pump?

[Dime Dave]

Dave you were talking about swirl pots? I have found several online...in 4 liters and 2 liters what should i be looking at? also what do you suggest for a lift pump?

 

Swirl tank size really doesn't matter. I would lean toward the 2 liter size or build one. I have a 1qt overflow cannister that I was going to add a couple ports to for a stalled SR project of mine.

 

Allstar P/N ALL36112 (MSRP $61.99)

 

Lift pump can be anything from an inexpensive Facet type

 

 

to a Holley Blue or

 

a Mallory 110 fuel pump.

[Dime Dave]

[NORTHDATSUN510]

Dave, thank you so much!!

[Tice]

They changed to hardlines except for just what was needed for flex at the suspension points and everything was good again.

 

Dime Dave, Are you suggesting that steel-braided hoses are basically more trouble than they are worth? You post has steered me far from even the idea of purchasing one now... :geek:

[Dawa]

if anything, the thing to take away from this is that braided lines still flex and cost more whereas

hardlines dont flex and are inexpensive.

[Dime Dave]

Dime Dave, Are you suggesting that steel-braided hoses are basically more trouble than they are worth? You post has steered me far from even the idea of purchasing one now... :geek:

 

Tice,

No I’m not suggesting that steel braid is not good for replacing rubber flex lines. By replacing rubber with steel braid you will have a firmer pedal. What I was trying to say was is if you start replacing OE hard lines with steel braid as well you can create a spongy pedal because steel braid does swell under pressure where hard lines virtually do not.

 

Maximize the amount of hard line and minimize the amount of steel braid and you will have a firmer pedal and better pedal feel.

 

And Dawa is 100% spot on about cost!

[Tice]

if you start replacing OE hard lines with steel braid as well

 

Ah-ha! Ok, I missed that bit somehow when I read through this thread the first time. Yeah, I could see that that would cause a few problems. LOL

[DatsunHiLife]

Thanks for this post. Taught me a ton.