so i am planning to sump my tank and run .5" lines (-8AN) from tank to carb. running about 500hp, so this should be about right. so here is the question;

in the interest of getting a head start, i was planning to run the -8 line from mechanical pump to the carb. i have not pulled the tank to weld in the sump or run the lines from the tank to the pump. I will soon, but some other work needs to get taken care of first. so will i run into problems running the large line after the pump with the stock line from the tank?

At 500 horsepower, maybe you need 1/2" plumbing to a mechanical front-mounted fuel pump. I don't know for sure; I chose to use an electric pump at the back so the pump didn't have to suck fuel through ~14 feet of tubing. And that'd be my suggestion to you:

Forget the 1/2" tubing, at 500+ horsepower 3/8" tubing is plenty--if you also put a high pressure (~14 psi) electric pump near the tank so you can "push" the fuel instead of "pull" the fuel; and then regulate the pressure downwards near the carb.

My 'Camino got a tank sump; if I had it to do over again, I wouldn't--I'd pull the sending unit and re-tube it. Granted, I don't have 500 hp. I keep thinking that if I get in a collision that injures the gas tank, the sump is very likely to come unglued from the rest of the tank and there'll be gasoline all over. That'd be less likely (but of course still possible) on a non-sumped tank.

To answer the question as it was asked, no you will not have a problem running a large line from the pump to the carb with a smaller line behind the pump.

Being a fluid gas is not compressible. Thus once the large line fills up with gas it does not know the size of the line behind it. As long as the smaller line can supply the fuel needed the larger line will carry it with no problem. If the smaller line behind the pump cannot supply the needed fuel it really does not matter the size of the line in front of the pump, it will not be filled whether it is 5/16 or 3/4.

Hope I understood the question.

Just had a class on fluid dynamics. Like stated above it wont make a difference, since all your worried about into the carb is volume flowrate, if anything flowrate will go up due to less friction in the larger line due to the fact that the fluid does'nt have to have as high of a velocity to flow the at the same volume rate to the carb.

At 500 horsepower, maybe you need 1/2" plumbing to a mechanical front-mounted fuel pump. I don't know for sure; I chose to use an electric pump at the back so the pump didn't have to suck fuel through ~14 feet of tubing. And that'd be my suggestion to you:

Forget the 1/2" tubing, at 500+ horsepower 3/8" tubing is plenty--if you also put a high pressure (~14 psi) electric pump near the tank so you can "push" the fuel instead of "pull" the fuel; and then regulate the pressure downwards near the carb.

My 'Camino got a tank sump; if I had it to do over again, I wouldn't--I'd pull the sending unit and re-tube it. Granted, I don't have 500 hp. I keep thinking that if I get in a collision that injures the gas tank, the sump is very likely to come unglued from the rest of the tank and there'll be gasoline all over. That'd be less likely (but of course still possible) on a non-sumped tank.

I was going with the -8 because that is what my engine builder told me to do. i know it might be overkill, but can't really go wrong with being more than adequate huh? being that i do fabrication of aircraft parts for a living, i was gonna tig weld it. no problem with bonding that way. also bending up hydruallic and fuel lines with a production mandrel bender is another part of my job, so fabbing the lines is easy for me as well. I like the simplicity and reliability of the mechanical pump. i do have a 170gph mechanical pump on it so that helps. I have not experienced any supply problems with the 3/8" line so far. i have not really stood on it yet due to the TH350 that is in it still. i am waiting till the TKO600 goes in it to really wring it out.

Just had a class on fluid dynamics. Like stated above it wont make a difference, since all your worried about into the carb is volume flowrate, if anything flowrate will go up due to less friction in the larger line due to the fact that the fluid does'nt have to have as high of a velocity to flow the at the same volume rate to the carb.

cool, that is what i was hoping was the case. i am a scuba diving instructor, so we got pretty deep into bernoulli's principle. i just wanted to be sure i understood correctly.

thanks fellas, i think i have it figured out.