Anyone know if a single flare is ok for the stock fuel lines? Are the stock lines seamless? I kinda doublt it. I wonder if places like Fine Lines are seamless.

Thanks,

John

 

Double 37

 

double because stock line is not seamless.

 

AN fittings use a 37* flare. A brake line flare tool only makes 45* flares.

 

Cool, that is what I thought. I'm going to find out if the Fine Lines stainless replacement line is seamless. If it is, a single flare is good?

Seeing as how rare and expensive a double flare tool is, I'd like to avoid it if possible. Perhaps a swagelok to -an (if it even exists) would be another solution as well?

John

 

Exactly. Hence my issue, 37 degree double flare tools are expensive.

 

lol, i honestly didnt even know there was a 37 degree double flare tool till today.

I have single 37 degree flares on my stock brake lines, no problems at all. Should i be concerned?

 

If you have a lathe you can make your own flare tools and cheap!!

 

As long as the line has a straight enough section near the end, you just need a nut and sleeve collar to make a connection to a AN fitting. No flare required. The flare is part of the sleeve. It's like a crush sleeve. When you tighten the nut, the sleeve crushes around the tube and prevents leaks.

You shouldn't need to make a double flare for a 37* fitting unless you're using it for high pressure hydraulic lines.

 

Why not use the insert from a normal flare tool to make the bubble?

The seat and cone is what makes the 37* angle, the first step is just making the bubble in which there is no real angle to speak of.

And, those tube nuts are rated to 50psi. Guys like me see more than 50 psi under boost with a 1:1 regulator. Guys with FMU's see even higher. Unless your running a carb.

-- Joe

 

I've worked with lots of (fairly) high pressure hydraulics (~6500 PSI) and don't ever recall seeing a double flare. Not saying it may not exist, just don't ever recall seeing one over the years.

That said, I'm not implying single is OK on brake lines because the brake line material seems considerably different than the material hydraulic fittings and hard lines are made from, and usually the hydraulic had a backup sleeve/ferrule between the flare nut and the actual (single) tube flare.

We don't do much with flare anymore though, it's pretty much all ORF or split flange these days in our hyd. systems.

 

Disclaimer: my only flare tool is 45°.

That said, I have never EVER, NOT EVEN ONCE, "settled" for a single flare on ANY joint. I don't care if it was power steering or brakes with pressures up in the 1000 psi range or more, vacuum, kitchen pumbing, fuel, or ANY OTHER THING. Can't see why, with a tool in my hand that makes double flares, how it would EVER be "A Good Idea" NOT to do so; or more accurately, "A Better Idea" to use a single than a double flare.

Having witnessed several cars burn to the ground on account of fuel leaks, I would DEFINITELY classify fuel FOR SURE as a place where I would MOST CERTAINLY NOT "settle" for a single flare, EVER, for ANY reason, at ANY angle.

JMHO.

 

I think I'm with you on this. I used a single flare on my fuel system, with a seamed OEM line and it leaks at the fitting at 50psi. I'm going to double flare it tomorrow. I think when I tightened it down, it split at the seam. A double flare I'd think would prevent that.

-- Joe

 

Since this thread came back to life, I think I'll add that I redid all my injection lines on my tunnel ram with hard lines. I bought a Rigid 37* flaring tool. It's not cheap at around $100-$130. You can buy the real cheap ones that look just like the 45* flare tools but I can't say how good the flare will look. The Rigid tool is so nice that even a blind person can make a perfect flare. It's impossible to overtighten and it makes a perfect flare.

To do a 37* flare, you need a nut and sleeve. Install both over the line, install flaring tool and make the flare. The sleeve sits against the back side of the flare and the nut holds it all tight.

My alcohol injection pressure at WOT and max rpm is in the 70-100 psi range.

 

Are you doing duble flares or are you using dom fuel line?

I took mine apart tonight and as I suspected, it cracked on the seam.

I'm not doing 37* flares though, I have a 3/8 to an adapter, although I technically do have 37* tube nuts from another project so I could flare the line that way but I'd have to wait a week for a new flaring tool to show up.

-- Joe

 

Sounds like a whole lot of stuff to accomplish nothing, what's wrong with the factory O-ring sealed connection ? Did someone manage to get that to leak with a good O-ring in there ?

 

Hard lines were rotted in spots. removed and replaced with new stuff.

Aftermarket fuel rails don't take saginaw fuel fittings.

-- Joe

 

Ah, the rotted stuff makes sense if you are replacing with regular fuel hardline.

I've just replaced the stockers with a set from another car, forgot you have to deal with that cars heavily rusting stuff.

As far as aftermarket rails, the lines can have the O-ring fitting at one end and whatever you need at the other end for the rail/regulator

 

There is absolutely nothing wrong with the stock connections. However, when going custom routed fuel lines, the saginaw flaring tool is very expensive plus the connects are limited and hard to get. Ever seen a saginaw bulkhead connection? I haven't.

This thread is quite old. I ended up using seamless line with single 37 degree flares. As has been pointed out, this type of connection is used on connections many times the pressure of anything in our cars. They are used for both commercial and military aviation. There is no question on the integrity of this type of connection. I ended up using the Rigid 377 tool for the flares, great tool. I have no question that the flares were done correctly.

John

 

Taking the stock ends from the rubber line off, machining off the collar and removing the hose leaves you with the stock end that a teflon lined stainless hose can be crimped onto.

 

That won't work for the corrugated hose I use.

Also, that is quite a lot of work and money for what is in my opinion no better than a proper 37 degree connection.

 

Its cheaper in the end, and not much work at all, for someone with a local hose & hydraulics shop.

But if you have no access to something like that, and needed to use AN stuff out of a catalog I can see its use.

 

The Rigid 377 tool only does singe flare. That's all it needs. The inside of the flare seats against the fitting. The outside of the flare is clamped by the sleeve which is held tight by the nut.

I just picked up pre-made brake line from the local auto parts store. I cut the double flare ends off and put the 37* flares on the ends. Brake line can easily handle 3000+ PSI. The 100 pounds of fuel pressure that I do is nothing.

The Ridgid 377 can do 37* flares up to 3/4" tubing. I'm glad I didn't cheap out on some cheap import piece of junk.

http://www.ridgid.com/Tools/458R-Rat...Tool/index.htm

 

Hrmm.. I know what your saying about brake lines and 3000+ psi, but I can't help but feel they put a double flare on for a reason.

I have some AN tube nuts but there is no sleeve. I'll have to google exactly what you have.

-- Joe

 

They use a double flare because of the type of fitting. It's called an inverted flare fitting. The flare nut is actually tightening and twisting down onto the back of the flare.

With a 37* flare, the sleeve pushes down onto the flare and doesn't twist against the flare as the nut clamps it down.

 

I see what you mean. The sleeve doesn't rotate.

-- Joe

 

The double flare process never forces the very end of the tubing to expand at any point during the process, in fact, it's actually slightly compressed in most cases, so there's no tendency (or at least, MUCH less) for it to split the tubing.

A single flare just widens out the end of the tube, which makes it thinner and tends to split it.

Doesn't really have so much to do with the extra ferrule.

Either a "common" or an "inverted" flare can be made single or double; the same thing happens to the tubing, the only difference is which way the threads on the nut and the body face. The actual tubing seat however is the same.

 

The double flare is there for a very good reason. Most tubes are welded. If you single flare a welded tube, the welded edge is on the sealing surface. This surface is not clean, so the connection doesn't seal. The double flare makes the outside of the tube, which has been ground down, the sealing surface. If you use seamless tube, all surfaces are clean and you can get away with a single flare.

All AN tube nuts should be used with sleeves. Usually they are sold separately, which is crazy.

 

Thanks guys.

So, I looked at what I had in the shop and my Holley made stainless lines have brass AN nuts with no sleeves, but it's a double flare. (I'd be happy to take pictures if nobody believes me).

I think I'm going to double flare the leaking connection I have now, then re-evaluate how I build fuel systems in the future.

-- Joe

 

Double flare cured the fuel leak.

Now I just need to find out why my iac passage sounds like an air raid siren at idle.

-- Joe