sevenracer HalfDork
12/18/22 11:25 a.m.

I am in the midst of adding a fuel pressure regulator to my car and upgrading the fuel pump. It's an 82 rx7 with a Turbo 13b swap. So, nothing in the fuel system is totally stock or unmodified.

When I put the car together earlier this year, I used as much of the stock fuel lines that are steel with bubbles on the end to clamp rubber hose. For all the new components I added, I just used hose barb adapters and rubber hose to connect to the hard lines. I also made up some NiCopp lines for places where the stock lines didn't work.

It all turned out ok, but I never got a good method for making bubble ends on the NiCopp lines. All i had was a cheap autozone tool intended to make single and double flares, not bubbles, and >50% of the time the line didn't expand uniformly - creating a lopsided bubble that was almost flat on one side. I don't have any leaks, but those Nicopp lines concern me a bit.


Now that I need to dive back in to add the fpr and larger pump, I'm revisiting options for my fuel lines.

My number one consideration is that space is tight on my car where all of the new components are. So bulky lines and especially fittings don't fit well, and the space to tighten fasteners is limited.

I don't particularly like AN fittings and braided lines. Pretty bulky, so not great in tight spaces, and pricey.

I instinctively prefer hard lines running on the underside of the car - thinking they will be less likely to get damaged.

Vinyl lines look to be easy to work with and not bulky - do they hold up well? Do they need protection from rubbing on the chassis?The only experience I have with vinyl lines are on my 2017 F150 where one of the lines split for no apparent reason. Also , not sure how to get the vinyl line to conform to all the twists and turns needed to snake through the chassis like the steel lines do.


so tldr:

1. What works well for non bulky fuel line and connections?

2. How can I make bubble flares on the hard lines I make? I couldn't get the cheap parts store flare tool to work well at all.


MadScientistMatt UltimaDork
12/18/22 12:06 p.m.

Where are you using bubble flares, and can you replace those with AN or brake flare fittings instead?

Dusterbd13-michael MegaDork
12/18/22 12:12 p.m.

You can borrow my mastercool and do bubble flares. And an flares. And iol co.e and help if you want. I still owe you for your hospitality on the ace rollbar.

jgrewe Dork
12/18/22 1:20 p.m.

You want a beading tool like this.

I have one that does three sizes of tubing. Let me know what you are working on specifically and if mine will work for you, you can use it. Just pay shipping back and forth.

sevenracer HalfDork
12/18/22 1:38 p.m.

Sorry, not clear. Not true bubble flares. Just standard Mazda fuel connections circa 1990.

jgrewe Dork
12/18/22 2:11 p.m.

That's what mine does. It is a miniature bead roller.

sevenracer HalfDork
12/26/22 6:34 p.m.

Minor updates.

Jgrewe - that looks like exactly the tool I need. I may take you up on your offer to borrow it, since I hate to spend a couple hundred bucks for something I will barely use.


I ordered some fittings to try to get a sense of how to mount/route everything.

I got some bad info off the an rx7 forum regarding thread size in the fuel rail. Supposedly, it was M14X1.5, but the threads are actually M12X1.25. I got a banjo fitting in the right size, but it doesn't sit flush to the rail, so I don't think it's going to work. 


I can't find an M12 X1.25 to right angle 5/16 (8mm) hose barb, but I can get an M12X1.25 to AN6. So, are AN fittings reliable? As in do the aluminum fittings stay torqued without safety wire? This one won't be easily visible/accessed, plus it's right above the turbo and exhaust, so very bad place for a leak. I feel more comfortable with tried and true rubber hose and hose clamps.

sevenracer HalfDork
12/26/22 6:40 p.m.

And this is the total fuel system (except banjo fitting to be replaced with something else). So many connection points (opportunities for leaks):

Dusterbd13-michael MegaDork
12/26/22 7:04 p.m.

Ive never had an an fitting spontaneously loosen. I don't think its an issue.

NorseDave HalfDork
12/26/22 9:10 p.m.

This is likely more than you want to spend, but I can vouch for it.  Thing works fantastically.  They (FedHill) used to rent it out.  It doesn't seem like they do that any more, but maybe give them a call.  Many years ago - like 10-12 I think - I redid my truck's entire braking system with all new Cunifer (NiCopp) hard lines.  I don't even know how many fittings it was, but it was a bunch, and I didn't scrap a single one, at least not because of the flare. 

A little hunting and manufacturer direct appears to be:

jfryjfry SuperDork
12/27/22 9:40 a.m.

Try running a short bolt down that hole to see if it also has the gap to see if the fitting is cockeyed or the surface. 

you can also use a set of calipers to check the parallelness of the banjo fitting

you could possibly file the surface flat or the banjo so they are parallel. 


an fitting, if done right, won't loosen, at least also in my experience. 

don't ever use those cheap flare tools.  They are a crap shoot. And crap. 

rigid makes a very good kit for about $100 that is completely worth it.   If you think a half-double flare will work and you want to be able to flare in the future, get something at least that nice. 

but borrowing jgrewe's sounds like a great solution. 

sevenracer HalfDork
12/30/22 10:12 a.m.

In reply to jfryjfry :

Good call on using calipers and a bolt to check flatness of the fuel rail. I'm traveling home now and will be working on this tomorrow.

Hard to believe it wouldn't be flat since the original fpr would need a flat surface to seal, but a prior owner of this fuel rail endeavored to powder coat it, so who knows the life it's led.

On the AN thing. I've heard that tightening them too much will cause them to leak, plus I'm always reluctant to crank down on aluminum parts vs steel. I have some - 10 AN oil lines on my racecar, and have needed to re tighten due to weeping at the fitting. No big deal on a car that is on a race car inspection schedule for a line that isn't much of a fire risk, but could be a really big deal on a fuel line above the exhaust. 

GameboyRMH GRM+ Memberand MegaDork
12/30/22 10:25 a.m.

I haven't had any problems with AN fittings loosening or leaking either (from 2 cars that use them for the oil cooler), but I use high-end fittings (largely because the reusable ones are cheaper in the long run). Overtightening them can cause them to leak, and once that happens it tends to be permanent. The finger tight to contact + 1/4 turn rule works well, there are also recommended torque tables for different fitting sizes. If in doubt don't tighten too much, you can always add tension but you can't un-deform a fitting, and AN fittings tend to still hold a seal when undertightened.

AngryCorvair (Forum Supporter)
AngryCorvair (Forum Supporter) GRM+ Memberand MegaDork
12/30/22 10:36 a.m.

That banjo fitting is berkeleyed. The bottom is not machined parallel to the top. Send it back.

wawazat SuperDork
12/30/22 2:53 p.m.

The vice mounted flare tool is offered by a bunch of suppliers and sometimes on sale.  I got mine at Summit on sale and with free shipping.  I've also seen it offered at Eastwood and Jegs.  The flares it makes are fantastic.


Pete. (l33t FS)
Pete. (l33t FS) GRM+ Memberand MegaDork
12/30/22 3:44 p.m.
AngryCorvair (Forum Supporter) said:

That banjo fitting is berkeleyed. The bottom is not machined parallel to the top. Send it back.

Yeah no kidding.  The surfaces are visibly not parallel with each other or the barb.  You can also see where the barb was undercut in the machining process.


On my GSL-SE rail, which has the regulator on one end and the pulsation damper on the other (no secondary injectors), I just tapped the PD end to, I think, 1/4" pipe and used a right angle 5/16 fitting.  Hasn't leaked 15 years later.

sevenracer HalfDork
12/30/22 9:23 p.m.

In reply to AngryCorvair (Forum Supporter) :

Good eye. Didn't catch that in the 5 minutes I spent testing it before my trip. Luckily, I guess, it was a 2 pack and the other one looks OK. 

sevenracer HalfDork
1/11/23 12:14 a.m.

Quick update.

At $30, I thought I found a reasonably priced solution in this Pegasus Racing beading tool for 5/16" tubing. I had used a larger version for a coolant line and it worked well, so I thought this would be a reasonable solution. Unfortunately, this smaller version just barely puts a ridge in the tubing. I wouldn't trust it to keep a hose from slipping off, so I'll be sending the tool back.

But I did refine my method and am now able to put a decent end on NiCopp tubing using the cheapo parts store flare tool. Doesn't work for steel line, the line slips back into the tool before it deforms, no matter how tightly it's clamped in the tool.

Part from Pegasus tool on left, my new refined result in middle, OEM on right.

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