I am trying to find out if all of the 71 b-bodys with either the 440 or hemi had the 3/8" dia. fuel line or if some had the 5/16" ?
I just ran across something odd on my 6-pack car. It has the 5/16" dia. line from the gas tank to the fuel pump. Yes it is a real 6-pack car and I have owned it since 1977. I also know the person who ordered the car new out of Chicago and he never changed it. He had the dealer undercoat the car when new and the tar undercoat is still on the lines and they still have the factory crimp clamps on the hose ends.
I wonder if it was a goof up on the assembly line or did some cars not get the 3/8" lines ?
I remember about 10 years ago a friend was restoring his 69 GTX and his had 5/16" lines but he figured it was a California emissions car because it had a vapor return line also.

I thought that only Hemi cars got the 3/8" line.

I'm pretty sure my 440 4v R/T has 3/8" line....

Supply-3/8

Return to canister-5/16

I've owned a few 69-72B with 440-4bbl and all had the 3/8" and 1/4" return line.
Thought the return is 1/4 not 5/16 but not positive.

Return is 1/4"

Thanks for all the input, Yes I agree the line should have been a 3/8" not a 5/16". I think it must have been a mix up on the assembly line. My return line is a 1/4" line and the vapor line is a 5/16".
This is maybe part of my problem when I raced it at the strip The carbs would run out of gas at 9o mph.
I am going to change the line to 3/8" but am I going to see any improvement when the fuel lines from the pump to the carbs are 5/16" ?

My 440 magnum had a 5/16" line. I've gone 12s at 109 mph, others have gone 11s with a 5/16" line.