Whats the "limit" with 5/16" fuel line? What are you guys running/how much power are you making? What HP level is it recommended to go to 3/8"? Im still running 5/16 on my Cuda with a "blue" pump

there was an informative discussion on this recently if that thread could be retrieved. the scientific way would be to add an isolated fuel presure gauge inside the car & see how much psi you have at the end and does it feel like it is laying down on the top end.

I've ran a Hemi in my Challenger at 150MPH for a few miles without running out of fuel with the 5/16 in line back in the 80's. However most of these fuel lines should be replaced now anyways and it only costs about $20 to buy a roll of 3/8" line to bend a better line. I think Fast68Plymouth has run into the 10's with a 5/16" line too. But there's just no reason to have that as the weak line.

Sheldon