I hijacked this from another thread. It's a very good question about the VP44 return line, and no one has answered it.

"So now to carry this one step further, shouldn't everyone increase size just help help the cooling action on the Injector pump. My next question here is, when I installed the fuel lines I was told I wouldn't gain anything by replacing the return line so I didn't and now I'm rethinking this. If I'm delivering 15 pounds of pressure through a larger line what is happening to all that pressure when the unused portion is routed through a smaller line. What's the backup gonna cause."

 

I was still wondering about this after no replied so I just put it in high performance also in the Holley Blue Thread, just so you can keep an eye on it.

 

Thanks,

 

the small return line not bleeding off enough pressure from high perormance lift pumps is what might have caused people to have hard starting with lift pump pressures higher than 20psi or so. More fuel circulating through the overflow would definatly help cool the injector pump. If the overflow is set at 8psi and you have a pusher pump system that can reach 30 psi of pressure that would be 22 psi of pressure going back to the tank which would provide some extreme cooling capability provided you could upgrade the overflow to handle that much fuel

 

Interesting. Is the overflow actually set at 8 psi, or is it used as an example?

 

How hard would it be to just run the larger fuel line back from the overflow valve? Disconnect the old put on the new, run it back to the return line on the tank and bam! its all done. Well, a few zip ties to keep it nice and neat.

 

Hmmm, this brings more questions to mind. Will the return banjo bolt have to be replaced? How does the return line attach to the tank? Is it a quick disconnect like the fuel line?

 

Is the limit on the return the line or the pump?

 

I'm not sure of the banjo size at the engine, but the return line at the tank feeds through the bulkhead and into a 5/16" (?) tube which returns the fuel into the bottom of the pick-up/sending-unit assembly. The stock pick-up and return lines inside the tank are the same size. Replacing them with A/N bulkhead fittings and 1/2" tubes would remove any chance of restriction at the tank.

 

While I don't know for sure, I would be surprised if the over flow valve in the VP could actually out flow the 5/16" return line.

 

I would have to agree with CTd nut until a larger overflow valve is out there I wouldn't see a whole lot of call for a larger line, that being said it wouldn't hurt either

 

I'd still like to know where all the excess fuel pressure goes and what damage is it doing to the seals in the pump, especially for these guys runnin twice and more the stock fuel pressure.