Bozang1

So I ordered a new fuel tank for my 72 cutlass. I'm going to be ordering new straps and sending unit too so it's all new. I plan on putting a 455 in there and was reading something that was saying about using a sending unit with a return line if running a big block. My car (currently small block) is a single line sending unit with no return in stock form and a sending unit is basically just to feed info to the gauge and is the route for the fuel so why would I need a return line? I don't plan on changing up (getting a different sending unit than what I have). I plan on running a single line unit so am I missing something???

joe_padavano

The return line routs hot underhood gas back to the tank to cool. This helps prevent percolation and vapor lock, which is even more important with today's gas. Olds used fuel return on cars expected to have higher underhood temps, usually big blocks and A/C cars.

Bozang1

So do you think I would need that sending unit with the return line? I really wasn't planning on it. I don't see how a big block would make any more heat than a small block. Other than just taking up a little more room under the hood thus allowing less room for cool air under there. But I just don't think it would matter. Whaddya think?

pogo69

your 455 should run fine without the return line and work of installing the line replacing the sender and fuel pump

Fun71

Well, 455 cubic inches of air/fuel burning generates more heat than 350 cubic inches of air/fuel burning; therefore, under the same conditions a BBO generates more heat than a SBO.

Bozang1

That's what I thought..thanks

MDchanic

I think that GM did not spend all that extra money developing the return line sender and fuel pump, and the routing of the extra line, and installing them on certain cars, for no reason.

That being said, you will probably be fine without the return line.

... Or, you will learn about the fun of vapor lock, a problem which has been extinct since... they started using return lines.



Defeats it soundly, eh?

- Eric