If your running a stock gas tank with a 3/8 sending unit, what is the point of running fuel line or return line in anything larger than 3/8. Isn't the flow restricted to the smallest diameter in the fuel system. The reason I ask is I'm going to a bigger electric pump (current holley blue) with more gpm and was wondering about the need to increase the fuel line and return line size? Thanks

My first question would be to show the engine combo that would require anything above 72 gph consumption. IMO , you may be returning more fuel to your tank than you use? If you had a large CI motor with dual carbs and were screaming at 7500, all day long, I would say no bypass is needed but very few street cars need this. I would consider a bypass line in event you are running EFI unit that requires 30-60 psi constantly. 3/8 line would be sufficient for this purpose. Stock fuel pumps on HI PO motors may require 30-40 gph. This is just my .02 .

I got tired of playing games with my old combo and purchased a 468 bb that in its current set up runs 10.60's. My concerns with the swap are the current blue pump with 3/8 lines (has return line and regulator) the driveshaft, and the axles. I think the blue pump is rated at 88 gph. If the motor is at 700hp I was thinking of at least a holley black, but didnt know about changing the fule line size, based on the 3/8 sending unit.

I got tired of playing games with my old combo and purchased a 468 bb that in its current set up runs 10.60's. My concerns with the swap are the current blue pump with 3/8 lines (has return line and regulator) the driveshaft, and the axles. I think the blue pump is rated at 88 gph. If the motor is at 700hp I was thinking of at least a holley black, but didnt know about changing the fule line size, based on the 3/8 sending unit.

Little more like what I ran with a 468, So I get your picture now. I used the Blue , which I see rated at 110 gph at 14# psi, with a reg, I ran one 1050 8896 Dom and 1/2 line all the way from pump with no bypass and regulated down to 7-8 psi at carb. No issues. I ran the 1/2 hard alum line . Yes, you may need that blue pump, with reg and use the 3/8 for return bypass, just to keep load off pump but still have plenty of volume. There are more expensive ways to do this but I would put my money where it counts.

I don't know how true this is but I've been told that on a street car you want to have the return/bypass system because it cools the fuel by returning it to the tank, supposedly without a return the fuel has a better chance of vaporizing in the line due to the heat of the fuel.

[QUOTE][I don't know how true this is but I've been told that on a street car you want to have the return/bypass system because it cools the fuel by returning it to the tank, supposedly without a return the fuel has a better chance of vaporizing in the line due to the heat of the fuel./QUOTE]

Old Man that is very true and the chances of vapor lock increase with the amount of heat a big block generates.

Do believe this but can't see why some stock fuel pumps have this little return nipple at the bottome of the pumps, and some don't. Also example is the first gen camaros, some have dual fuel lines and some don't.

Something I was just thinking about is the Holley fuel regulators, unless they have changed, they just regulate fuel pressure, there are no bypasses with outlet lines, or at least the ones I used at one time. I guess they engineered the pump to bypass internally.

I do use the return line because it was a cure for vapor lock . My biggest concern is the ramifications of the new bb horespower. Drive shaft, axles, and fuel delivery. I'm concentrating on fuel delivery right now, I dont see the reasoning behind increasing fuel line size anywhere if the sending unit is 3/8, as this would be the weakist link in the systems ability to move fuel or would 3/8 be fine with a 140 or 150 gph vehicle, if not what to do?

I do use the return line because it was a cure for vapor lock . My biggest concern is the ramifications of the new bb horespower. Drive shaft, axles, and fuel delivery. I'm concentrating on fuel delivery right now, I dont see the reasoning behind increasing fuel line size anywhere if the sending unit is 3/8, as this would be the weakist link in the systems ability to move fuel or would 3/8 be fine with a 140 or 150 gph vehicle, if not what to do?

I have been in your shoes, all I can say is try it, prove your point. I agree, it wont matter if you had 1/2 lines to carb , if your suction point is limited to 3/8's opening.
Whats the concern on drive shaft and axles? You need them but if you break them, you proved your point, need something better.

I'm not sure if stock axles and stock driveshaft can take the new and improved hp. I'm pretty sure I will be changing to an aluminum 3.5 driveshaft with 1350 ujoints, dont want that breaking at track. Axels, I have no clue about, anybody want to donate a 9 inch ford for the cause?

Moser? Strange? Mark Williams? for axles, Don't forget drive shaft loop.

I've got a loop, what do I do get for axels, more splines? What else what have to be changed?

I've got a loop, what do I do get for axels, more splines? What else what have to be changed?

I have a 9" in my 99 T/A, it's build for drag racing and has Strange 41 spline light weight steele axles in it. I think it can handle just about anything.

I've got a loop, what do I do get for axels, more splines? What else what have to be changed?

Axles spline needs to match your diff carrier splines. This does not mean that one of the companies dont' have a stronger replacement axle for what rear you have. You can upgrade.

zdld17,
How did the 468 eat your wallet, their is something wrong with one of your pics, your front wheels arent touching the ground? LOL

To build, was expensive and get to where it was, broke every part I had spare to get 9.70 @136 to out run the vett in another picture. 3150# car with a 468 , steel heads, th400/5500 stall , pontiac rear, 5.86 gear, From that point, I never had problems. Just getting there. Sure miss that car form the 80's. Motor was still flying when I sold it.

Mine is teaching me alot literally and monetarily. I have learned to take on alot more than I used to be willing to try, but it's the info I get here that helps the most.

For me, it passing on all I know to others and absorbing what others give, that is what makes this forum so great.