TheSamba.com :: View topic - Metal Fuel rails.. GoWesty? VanCafe? Others?

Wed Apr 03, 2019 11:13 am

HackAl wrote: The test in the video is at 100 psi. What is the normal operating range for the Digifant fuel injection system?

I think it's in the Bentley but I recall pressure testing my fuel lines at 55 psi after replacing them. I forget if the normal pressure is 55, 50, or 30 psi - but certainly less then 100 psi.

My VC rails are drip free going on about 8 years.

Wed Apr 03, 2019 11:46 am

The Machinist wrote: I have instructed my employees to hold the pressure for a few seconds before releasing it to make sure a leak doesn't slowly develop and push the sealant through.
A pneumatic test that lasts only seconds doesn't seem to me to be much of a test. I would think a proper test would require the pressure be applied for at least a few minutes.

Wed Apr 03, 2019 2:04 pm

The Machinist wrote:

The thread sealant debate is interesting. The Loctite 545 that GoWesty uses is intended for fine-thread applications and is not for NPT threads. It looks like a good application for the GW fuel rails because they drill a much smaller than stock hole through the body and use small fittings. The 3/8 NPT plugs that I use allow a bore that is closer to the original plastic fuel rails. The thread on these bigger plugs seems like it could be too coarse for the 545.

In all my research I am still coming up with Permatex 59235 high-temperature paste as the best for this application. We apply the paste to the thread and torque the plugs to spec.

Question for you Machinist: What's the advantage of using Permatex 59235 over the 56521 which retains 75% strength with gasoline vs the existing 40%? Both appear to be NPT-thread worthy. The Loctite 545 is rated at only 300 degrees F as is the gas-friendlier 56521.

Wed Apr 03, 2019 11:59 pm

djkeev wrote: Well....... for what its worth, my GoWesty assemble them yourself fuel rails continue operating leak free after years and years of use.

Possibly assembly "technique" plays into this?

Dave

In my experience the assembly technique required for the original round Gowesty metal fuel rails is to crank the fittings down far tighter than you would ever consider doing for any other pipe assembly involving brass and aluminium.

The instructions give no torque specification so I fitted them with the sealant provided reasonably firmly without risking stripping threads. They seeped so I did them again and they still seeped so I got my money back and bought some Van Cafe fuel rails which have been fine. To me, there is something not right with the thread design that you have to crank the fittings on the Gowesty ones down so tight to avoid leaking.

I think it is a good sign that although someone has had a problem with the Van Cafe rails that both Mike and the Machinist have responded on here and are trying to review this and prevent it happening again.

Thu Apr 04, 2019 5:28 am

Just curious, but what's the advantage of having the customer crank the gowesty fittings on?

Thu Apr 04, 2019 6:54 am

Customer assembly means vendor isn't liable for results. If vendor assembled then they would almost have to claim they pressure tested as well. Price of item would go up, fewer sales, more liability.

Taper threads require a sealant to work. There's no sealant I would ever ever trust for long term use with gasoline. Taper threads are also harder to machine. GW's "design" depends on all those taper threads to be customer sealed, it's basically a back-yard approach, not a well-developed product, and the failure rate reflects it.

The VC manifolds are beautifully made but could have simpler machining and assembly and higher reliability by tapping straight threads and using shouldered plugs with sealing washers on the ends.

GW could do similar but shouldered barb fittings are much more expensive and with so many their price would probably not be very attractive.

Thu Apr 04, 2019 8:31 am

VdubVanner wrote: Question for you Machinist: What's the advantage of using Permatex 59235 over the 56521 which retains 75% strength with gasoline vs the existing 40%? Both appear to be NPT-thread worthy. The Loctite 545 is rated at only 300 degrees F as is the gas-friendlier 56521.

I went with the high-temp paste because I wanted to be sure the seal would hold even if the engine overheated. Looking at the performance numbers, I am considering switching to the 56521. It seems that 300° may be safely beyond the highest temperature ever present in the engine bay.

Thu Apr 04, 2019 8:35 am

tencentlife wrote: The VC manifolds are beautifully made but could have simpler machining and assembly and higher reliability by tapping straight threads and using shouldered plugs with sealing washers on the ends.

I have been looking at other options for sealing the end. I am not sure exactly what setup you are referring to here. Would you be willing to show us?

Thu Apr 04, 2019 9:01 am

Gotta love a thread like this.

Questions jump in my head! So, if the end product needs intervention by the purchaser so the vendor isn't liable, why don't we come up with a design that most of us could agree would be a better plan.

Here is one I came up with: 6" or 8" long steel pipe nipple, end caps, drill for smaller threaded nipples for the fuel lines to come off. Flux and braze the threads for the end caps and smaller nipples. I think brass fittings would be fine too, brazed in place.

Half an hour at the hardware store, an hour with the drill press and tap, and some time with a torch. $70-$80 worth?? Peace of mind?

That should settle qualms about what sealant to use, for sure!

Thu Apr 04, 2019 11:00 am

The Machinist wrote: tencentlife wrote: The VC manifolds are beautifully made but could have simpler machining and assembly and higher reliability by tapping straight threads and using shouldered plugs with sealing washers on the ends.

I have been looking at other options for sealing the end. I am not sure exactly what setup you are referring to here. Would you be willing to show us?

Simple, use a shouldered plug, like a drain plug, you can find them in hex-head and socket-head types in many thread sizes. Or even a short hex-head machine screw.

Use a fiber, alu, or copper crush washer to seal. Tubular crush washers in copper or alu are most tolerant of low-precision faces. You would want to use regular or fine thread to produce predictable compression of the seals. You're already milling your manifold ends flat so the sealing surface is there.

No need to worry about dissimilar metals which is a concern with pipe plugs, the seal here is between flat sliding faces and will tolerate differential expansion. Brass would be closest to alu in expansion rate, but hard to find cheap shouldered plugs or bolts in brass. In a steel plug or bolt, a galvanised finish would be fine, the business end is immersed in gasoline. Stainless is a crazed obsession with people here but wasted money in most applications and this is one of them, plus the cost would make your product too expensive for no real benefit.

You're using a 3/8" pipe plug now, you could trade that for M16 or 5/8" thread to keep the large interior volume you're already producing (which I think is smart). Those aren't the most common thread sizes in drain plugs but they're not hard to find. Here's just one place that has an M16 shouldered plug with decent pricing at 79cents for 100 pcs. and fiber washers 8cents per 1000pcs.

http://www.oildrainplug.com/#Oil%20Filter%20Magnet0

This way you'd have a pretty predictable sealing mechanism that once you find the right combo of plug, seal, and torque by testing, can be assembled dry or with light oil and not even need pressure testing of every copy like pipe threads require, just spot sampling should suffice to keep you honest.

Anyway, that's how I would approach this, I've dealt with pipe thread more than I care to admit and a machined seal is always easier to machine and more predictable.

Fri Apr 05, 2019 9:59 pm

tencentlife wrote: Simple, use a shouldered plug, like a drain plug, you can find them in hex-head and socket-head types in many thread sizes. Or even a short hex-head machine screw...

Thank you. This is giving me some ideas.

Sat Apr 06, 2019 11:42 am

I wish you all the best with the re-design of your rails because they are real pieces of artwork. Once those two threaded ends are sorted out, I'm getting in line for a new pair.

Sun Apr 07, 2019 9:42 am

the below is an aluminum air distribution manifold that was suggested a while back for construction of a fuel rail. notice the TWO threads available for sealing, on NPT no less. manifold is still in my fittings bin needless to say.

i'm pretty confident in the plastic fuel rails but i've done two things... one, cleaned them off really well and fully inspected for cracks, and two, oriented the 'cap' to face the rear so that i can see any weaping easily. i carry a spare with 2 injectors mounted for quick swap out.

Sun Apr 07, 2019 10:15 am

If you are referring to my posts, that is not exactly the cheapo manifold I used although it is similar. The one I used was 1/2 that length. I had zero leaks.

In this case I do not see how additional threads would equate to reduced risk of leakage or reduced risk in general. The two threads shown are certainly enough material to prevent the fitting from coming loose under fuel pressure. It seems to me that additional tapered threads would just be more likely to mask a case of poor thread machining and delayed leaking as folks have been complaining about with the more expensive options.

Sat Jul 20, 2019 9:24 am

Anyone use the RJE Rocky Jennings aluminum fuel rails?

https://www.thesamba.com/vw/classifieds/detail.php?id=2002224

Any comments/problems regarding them?

Sat Jul 20, 2019 11:27 am

DanHoug wrote: the below is an aluminum air distribution manifold that was suggested a while back for construction of a fuel rail. notice the TWO threads available for sealing, on NPT no less. manifold is still in my fittings bin needless to say.

i'm pretty confident in the plastic fuel rails but i've done two things... one, cleaned them off really well and fully inspected for cracks, and two, oriented the 'cap' to face the rear so that i can see any weaping easily. i carry a spare with 2 injectors mounted for quick swap out.

xlnt point re the number of threads

https://fieldfastener.com/2013/04/23/rules-of-thumb-for-fastening-and-joining/

safety margin is important for a thing full of gas located above the spark plugs (!!)

Likewise, the plastic ones are worrisome, even if visually inspected as per your post above. I suspect they may not weep then fail, but could fail quickly (w/o weeping, or after just a short period of weeping).

The plastic ones are old and plastic ages...

OTOH, I have not (yet) replaced mine...

Sat Jul 20, 2019 12:41 pm

Why not just machine a plug out of the same material that fits into a recess on the manifold, then TIG it in place and be done with it. No threads period.

Thu Aug 01, 2019 11:57 am

After trying to track down the cause of the leak, it seems that the fuel rail in question may have been disassembled to be cleaned out and then reassembled and shipped without a leak test. This is just a theory that I can't confirm. I have tightened up the process and I personally check to make sure the parts are properly cleaned before sealing now. I had a bad experience with one employee who is no longer with us. His attention to detail was lacking.

After researching the thread sealant, we have switched to the high-performance Permatex sealant. I have looked at other methods of sealing. They all start to get expensive. We have delivered hundreds of these since we started to leak-test them. As far as I know, one weeped a little in 2017 and CJVango's developed a leak after installation in March.

Thu Aug 01, 2019 12:41 pm

Farfromslow wrote: Why not just machine a plug out of the same material that fits into a recess on the manifold, then TIG it in place and be done with it. No threads period.

Because in production you avoid welds wherever possible. Why? Welds are expensive!

Fri Aug 02, 2019 8:37 am

The Machinist wrote: After trying to track down the cause of the leak, it seems that the fuel rail in question may have been disassembled to be cleaned out and then reassembled and shipped without a leak test. This is just a theory that I can't confirm. I have tightened up the process and I personally check to make sure the parts are properly cleaned before sealing now. I had a bad experience with one employee who is no longer with us. His attention to detail was lacking.

After researching the thread sealant, we have switched to the high-performance Permatex sealant. I have looked at other methods of sealing. They all start to get expensive. We have delivered hundreds of these since we started to leak-test them. As far as I know, one weeped a little in 2017 and CJVango's developed a leak after installation in March.
ehh, my Passenger side leaked until I tightened the end plug, took twice to get it fully leak -free- First tightening got rid of faster leak and all appeared okay, then a few weeks later tightening it again got rid of a Cold Engine only seepage. at least the fuel residue left traces for me to easily see that it had been leaking. Drivers Side has always been leak free.
I had noted this in another post, or maybe it was earlier in this post.... :P
Anyway, my Van Café Manifolds have behaved ever since then with zero issues. :)

AND, considering what some PO left me in the way of Original VW fuel rails with a 'slight' modification to one of them.....It's a wonder one of the rails didn't set the poor Vanagon on fire in the past... :shock: