8 cylinder front engine iconic vehicle
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By Sazerac
#85378
Hi All

We have seen many threads in other places about the right methods to attach fuel hose to fuel line fittings. The best practices here are clear. What we have seen little discussion about is the actual material of the fittings to which the hoses are affixed and that we screw together.

When I recently replaced the fuel damper under the airbox I did quite a bit of testing and temperature cycling to make sure that I did not create any leaks. To my chagrin and consternation, on the first temperature cycling I found a weeping line, one that I hadn't even touched. This was the hard factory steel fitting to the aluminum fuel cooler. These lines had been replaced say 4.000 miles ago.

This led me to think about GB's lines, which I have on both my GTs. His fittings seem to be aluminum. This means that by using his lines I have introduced many steel to aluminum connections in my fuel system. Whereas the steel fittings are virtually indestructible, how are people tightening aftermarket lines like this? Is there any evidence to suggest that material differences (say CTE, etc.) cause these lines to loosen, if not tightened to a certain threshold?

I repeat this thread is not indicating that one of GB's lines failed. It is rather the opposite, I noticed a factory steel to aluminum connection that was weeping and am now wondering about other connections simply because I introduced aftermarket parts increasing the number of steel to aluminum connections. So, how are people tightening these? Are these material differences an issue? What's your opinion?
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By hans14914
#85477
Most people actually overtighten aluminum fittings and deform the seat. Its actually pretty difficult to get the "torque" correctly. Pegasus has a nice guide on the specs and real-world method to seat AN fittings:

https://www.pegasusautoracing.com/docum ... =TECH00157

This is somewhat different than a metric fitting, and dissimilar materials, but a good primer on the subject.

I am in the minority, and actually prefer ORB or radial o-ring sealing fittings, such as J2044 standard, as they do not suffer the tightening issues for a metal-to-metal sealing seat. Most people will state that the o-ring has a useable service life, and can fail. In my experience, it is more likely to have a metal-to-metal interface not get seated properly than the o-ring to fail.

I my designs, I try to adapt the original fitting with a permanently installed metal-metal interface that will never need to be broken, and then go to o-ring seals for every junction in-between. Again, that is a minority opinion, but I am just a Viton o-ring seal person.
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By ROG100
#85494
We reverted back to rebuilding the original hoses with the steel fittings.
I have sold a number of fuel hose variations over the years including GB's.
They can all fail in varying degrees. Essential to check them every 6 to 12 months.
Checking is pretty easy to do on a regular basis.
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By worf
#86098
I've nothing to add other than that I will be revising my fuel leak test procedure to include a second leak test after a heat cycle.
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