[DeTomaso] steel vs. aluminum fitting to mate an AN fitting to a fuel rai...

[JDeRyke at aol.com]

Sort of depends.... Aeroquip 6061-T6 aluminum AN fittings are used in all 
military and most passenger aircraft for lightness, at values up to 3000 psi 
(certain failure at 4000 psi), but non-AN hot-rod type fittings might be a 
guess as to their safe pressure range. Stainless steel is used in very 
high-temp jet engine fuel and hydraulic control applications. For EFI, high 
quality aluminum fittings in an aluminum rail should seal nicely at all 
temperatures and not leak under any possible EFI pressures (usually 35-65 psi). 
Suggest using use anti-sieze on the threads. I currently use aluminum ANs on: 
fuel (6-8 psi)
brake (1200-1400 psi)
clutch (350 psi)
A/C (150-200 psi)- 
all for lightness.
But if there's a chance of impact to the outside of a fitting, steel should 
be used; aluminum doesn't like bending!   Thats why I suggest NOT using 
aluminum brake fittings for the bulkhead fittings where they reach through the 
rear trunk area, 'cause when we climb back there to work, those things can 
be stepped on and a cracked brake fitting is plenty-trouble! FWIW- J Deryke