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Upon research to find what size 1st gen's fuel supply lines are, I was finding that 5/16" was the common answer, and I also confirmed this via measuring, so that way I would know which size to get for the hardline to AN fitting. However, once I actually received the fittings, I noticed that they did not fit onto the stock fuel hardlines but did fit onto my Holley 465 CFM carburetor inlet (not sure about the stock Nikki but I still have mine around and could verify if requested). It turns out that the stock fuel supply lines are actually 8mm and NOT 5/16". 5/16" is actually ~7.94mm when converted to metric, so fittings that were precisely machined (such as Earl's in my case) will not fit 8mm hardline. My solution to this was to buy a new hardline in true 5/16" and replace the original 8mm hardline, but a few members of this forum said they were able to 5/16" AN fittings onto their 8mm hardlines. This seems to largely depend on what brand of fitting is purchased and its tolerances. If anyone has converted a 1st gen fuel system to AN, please comment below what fitting(s) you used and also if running new 5/16" hardline was required or not.
I replaced my fuel lines with 3/8 NiCopp. 6AN from multiple manufacturers but most Beijing from .. sorry Being from Amazon (Evil Energy) . I have not ran fuel through yet though I have ran filtered air through as a stress test to catch leaks. Leaks that seemed to be from my inexperience in installation.
So you are going to be running the Holley, what about the fuel pump, have you upgraded that also?
Reason I ask is you might run into an issue with the OEM return line diameter I think all 12A cars were 8mm feed and 6mm return.
I installed an aftermarket fuel pump and could not get my fuel pressure low enough, and had to run a new 3/8" aluminum hardline. To go between the hardline and hose, I installed -6AN tube tube nuts and flare, and then used -6AN to hose barb adaptors.
Not sure the scope of your project and if you will have issues with stock return line diameter, and what about your fuel pressure regulator? I assume your FPR is what connects to the chassis hardlines and then its a straightforward NPT thread (usually) to go to your carb.
So you are going to be running the Holley, what about the fuel pump, have you upgraded that also?
Reason I ask is you might run into an issue with the OEM return line diameter I think all 12A cars were 8mm feed and 6mm return.
I installed an aftermarket fuel pump and could not get my fuel pressure low enough, and had to run a new 3/8" aluminum hardline. To go between the hardline and hose, I installed -6AN tube tube nuts and flare, and then used -6AN to hose barb adaptors.
Not sure the scope of your project and if you will have issues with stock return line diameter, and what about your fuel pressure regulator? I assume your FPR is what connects to the chassis hardlines and then its a straightforward NPT thread (usually) to go to your carb.
I'm currently running a MSD 4070M for my fuel pump which has a 6 PSI internal regulator. Due to the style of carb I'm using (Holley 465 CFM) a return line is not necessary so it is capped in the bay at the moment. Fuel pump
