I am putting a stock 425, turbo 400, Edelbrock 4 barrel carburetor with a mechanical fuel pump in a 52 Buick. Will 5/16 diameter fuel line be adequate or do I need 3/8?
Let's get some details here. Are talking about running 5/16" from the tank to the pump, and then from the pump to the Carb? If so then depending on how many bends you end up having in the overall lenght of the line and the severity of those bends you looking at a fuel delivery volume at the Carb that can support 350 hp safely. This all being said if it where me and if I was installing new line from front to rear I would atleast want 3/8" tube from the tank pickup to the pump.
I just looked at what is on the car from the factory it is 5/16. There a two 90* bends up to the fuel pump from the tank. So if I am right at the "edge' I will go to the 3/8 inch. I should probably change the line anyway. The pick- up tube is 5/16, I suppose I could braze in a 3/8 in place of the 5/16 but the fuel pump is still 5/16 inch, pretty hard to change. Thanks for your ideas.
In short bursts sometimes available volume is as important as flow. And even with the constriction of the 5/16th pump overall the 3/8th line will allow the pump to do its best. A fresh pump would be good while you’re at it!