Fuel system upgrade...got some questions

[travis]

I need to upgrade the fuel system on my truck from it’s existing dual tank and 5/16” line setup. I’m in the process of building a 340-350-ish HP 351w, but the dream is to some day build a 408 with closer to 500 HP. Is a -8 line big enough to feed 500hp with a Carter superpump mechanical? Is there any downside to running an overkill setup in the meantime?

My 2 biggest questions are...1) what is the best way to run a -8 line into the fuel tanks, without resorting to sumping both tanks? Can I just drill a hole in the existing “plate” (I’m not sure what it is called...where the existing pickup line and fuel level sender are mounted), feed the -8 line in, bend it to match the existing 5/16” line, and weld it up around the hole? And 2...what do I do about the switch over valve that switches between tanks? I’d prefer to keep the dual tank setup, but the only available valves I have found are 5/16” or 3/8” in/out...which would be a restriction.

[tresi]

3/8 is large enough for 500 hp on gasoline.

[SupStk]

I've read 3/8" line will support 600 HP. There are lots of variables that will make a difference. Some are, length of the line, number of bends, type of fittings, is the pump sucking or pushing fuel?, how close to the exhaust?
On the fuel sender part, if a bigger one isn't available (many replacements come with 3/8) you can do what was mentioned.
On the transfer switch, if its electric you are probably stuck unless one from a different application can be substituted. If manual, there are ones that have ball valves with 3/8 holes.

[travis]

3/8” makes life easier, but so far I have found no fuel senders bigger than 5/16”...even for 460 applications??? Same fuel tanks are used in the F250’s and F350’s of that era...seems crazy that an application intended for heavy towing would use such a dinky fuel system

[cjperformance]

www.scintex.com.au/collections/automoti ... tion-valve

This will do the trick !

[SupStk]

That being the case, you will have to modify your existing senders.

[cjperformance]

I need to upgrade the fuel system on my truck from it’s existing dual tank and 5/16” line setup. I’m in the process of building a 340-350-ish HP 351w, but the dream is to some day build a 408 with closer to 500 HP. Is a -8 line big enough to feed 500hp with a Carter superpump mechanical? Is there any downside to running an overkill setup in the meantime?

My 2 biggest questions are...1) what is the best way to run a -8 line into the fuel tanks, without resorting to sumping both tanks? Can I just drill a hole in the existing “plate” (I’m not sure what it is called...where the existing pickup line and fuel level sender are mounted), feed the -8 line in, bend it to match the existing 5/16” line, and weld it up around the hole? And 2...what do I do about the switch over valve that switches between tanks? I’d prefer to keep the dual tank setup, but the only available valves I have found are 5/16” or 3/8” in/out...which would be a restriction.

Yes, just mod the existing sender/pickup as you described. When i do this type of thing i remove the original pipe and open out the hole it went thru to fit the new bigger pipe in. Bend it up to suit and weld/solder it back into place.