Fuel hard lines to regulator?

[richtersand]

Hi all, quick question for the gurus here. I noticed the norm is to run the hard lines to engine bay and then flex lines to the regulator that’s a couple feet away. Why not keep going with the hard lines all the way into the regulator?

Also, it looks like this is the required adapter for the Coyote fuel rails. I am assuming I need two of these. Can anyone confirm this is what I need? Thanks!

https://www.summitracing.com/parts/rus-640853

[edwardb]

Agree there's probably no technical reason you couldn't do hard lines all the way to the regulator. Practically speaking, are you good enough to get the bends just right and the two connections aligned? Additionally, I try to do my hard lines with no unions. So one piece from the firewall back to the filter for the feed and a flex line to the pickup for the return. That means just a simple right angle at the footbox or firewall and then flex over to the regulator. I wouldn't want to try to do all that with one piece.

For all the -AN connects on 3/8-inch hard line plus the connection at the Coyote fuel rail, I highly recommend Ham-Let Stainless Steel 316 Let-Lok Compression Fittings. Absolutely bullet proof and rated for way higher pressures than you'll ever see in this application. I get them from Breeze: https://www.breezeautomotive.com/shop/fitting-3-8-od-tube-to-06an-male-316-stainless-steel/. That Russell Performance part is OK. But this is a lot better IMO.

[bobl]

If the regulator is mounted to the body there is some movement and vibration. A hard line would fail. If it were securely mounted to the frame and the hard line secured very well it may work, but probably not worth the risk. With flex line on both ends things can move around without creating a stress point.

Bob

[edwardb]

If the regulator is mounted to the body there is some movement and vibration. A hard line would fail. If it were securely mounted to the frame and the hard line secured very well it may work, but probably not worth the risk. With flex line on both ends things can move around without creating a stress point.

Bob

As a general rule that's true. I left out vibration in my response though because in these builds the regulator is always installed on the chassis. Not the body.

[Al_C]

I agree with Edwardb that it's best to avoid unions on the fuel line. Where I differ is on the specific material: I used flex line for the whole line. I have one 3/8" line running from the fuel filter in the rear all the way to the regulator. My return line is also a single flex piece running from the regulator back to the fuel tank.

[richtersand]

Agree there's probably no technical reason you couldn't do hard lines all the way to the regulator. Practically speaking, are you good enough to get the bends just right and the two connections aligned? Additionally, I try to do my hard lines with no unions. So one piece from the firewall back to the filter for the feed and a flex line to the pickup for the return. That means just a simple right angle at the footbox or firewall and then flex over to the regulator. I wouldn't want to try to do all that with one piece.

For all the -AN connects on 3/8-inch hard line plus the connection at the Coyote fuel rail, I highly recommend Ham-Let Stainless Steel 316 Let-Lok Compression Fittings. Absolutely bullet proof and rated for way higher pressures than you'll ever see in this application. I get them from Breeze: https://www.breezeautomotive.com/shop/fitting-3-8-od-tube-to-06an-male-316-stainless-steel/. That Russell Performance part is OK. But this is a lot better IMO.

Thanks for the feedback. I am working with nickel/copper, so I am hoping getting a good fit across that distance will be more manageable. I am planning to run the flex line to the tank and I will try to make the run with hard line through to the regulator. If it turns out it's too hard to get a good fit, I can always cut the line and transition to flex.


If the regulator is mounted to the body there is some movement and vibration. A hard line would fail. If it were securely mounted to the frame and the hard line secured very well it may work, but probably not worth the risk. With flex line on both ends things can move around without creating a stress point.

Bob

Roger that. Thanks for pointing that out. As edwardb points out, the plan is to mount to the chassis as he did on his 20th anniversary build.


I agree with Edwardb that it's best to avoid unions on the fuel line. Where I differ is on the specific material: I used flex line for the whole line. I have one 3/8" line running from the fuel filter in the rear all the way to the regulator. My return line is also a single flex piece running from the regulator back to the fuel tank.

My buddy tried to talk me into going flex all the way around. I'm no expert on the subject, but I did read a lot about how the material degrades over time and it's actually very hard to realize the degradation happening because it's covered by the braided SS. Given I hope to drive this car for decades to come (I've had my '68 vette for 20 years now!) I am going with hard lines as a long-term investment. To each his own, and I've noticed a lot of people going with flex, but my personal preference is the hard line...

[egchewy79]

Use PTFE lines and you won't have to worry about degradation of rubber ones

[bobl]

As a general rule that's true. I left out vibration in my response though because in these builds the regulator is always installed on the chassis. Not the body.

So I shouldn't have mounted mine to the fender? LOL What I was actually referring to would be the unsupported aluminum firewall or even 3/4 tube structure which are subject to movement and vibration.