Fuel pump question

[72c20customcamper]

I’m putting in a Blue Print motor and the fuel pump they recommended already have it in hand has only an inlet and outlet Holley #12-834 7.5 psi . My truck has the return line to the tank . Question is do I need to have it because both my 68 trucks don’t have it . Or should I just get a stock replacement ?

[RustyPile]

If your truck (you didn't mention the year) has the return line, then yes, you need to install the pump designated for that type system. Fuel formulation has undergone drastic changes since 1868. Modern fuel injection systems operation pressures are upwards of 5 - 10 times the operating pressures of the carburetor era. Today's fuel formulations are prone to vapor lock at carburetor fuel pressures. A fuel return system on these old vehicles is a good step toward preventing vapor lock..

[72c20customcamper]

Originally Posted by RustyPile

If your truck (you didn't mention the year) has the return line, then yes, you need to install the pump designated for that type system. Fuel formulation has undergone drastic changes since 1868. Modern fuel injection systems operation pressures are upwards of 5 - 10 times the operating pressures of the carburetor era. Today's fuel formulations are prone to vapor lock at carburetor fuel pressures. A fuel return system on these old vehicles is a good step toward preventing vapor lock..

Don’t have it on any other old car I have they only get non ethanol gas and never have had vapor lock . This is on my 72 it has no vapor canister or pollution controls other than PCV .

[dmjlambert]

My vote is try it since you already have it on hand. Plug the return line. I have a 69 with fuel pump and tank not having a return line and haven't had vapor lock and I run with gasohol. But I have a Quadrajet and ram horn exhaust manifolds and clutch fan, which may be a completely different setup. 7.5 psi is high to pair with some carburetors, but a regulator would probably solve that if needed. Now that I type this I better knock on wood and hope I don't start getting vapor lock.

[72c20customcamper]

Originally Posted by dmjlambert

My vote is try it since you already have it on hand. Plug the return line. I have a 69 with fuel pump and tank not having a return line and haven't had vapor lock and I run with gasohol. But I have a Quadrajet and ram horn exhaust manifolds and clutch fan, which may be a completely different setup. 7.5 psi is high to pair with some carburetors, but a regulator would probably solve that if needed. Now that I type this I better knock on wood and hope I don't start getting vapor lock.

My thinking is that vapor lock would be caused in the feed line to the carb since fuel would sit in it when the bowl is full . A return at the pump would only keep the fuel moving in the line from the tank to the pump. Not much heat there with a factory setup . The pump is matched to the Holley carb on the new motor . This will have rams on it too . Putting a Cold Case radiator and fans on the truck . I guess I’ll try it if it don’t work out I’ll use the Holley pump on the engine going in the 68

[68 P.O.S.]

I put an Edelbrock fuel pump on my 72 with a return line. What I did was block the return line and bought a vented gas cap. It worked fine and I had no issues with it, until I took the trcuk apart years later. Make sure the pressure works with your carb, or else you'll get flooding and starting issues.

[72c20customcamper]

Originally Posted by 68 P.O.S.

I put an Edelbrock fuel pump on my 72 with a return line. What I did was block the return line and bought a vented gas cap. It worked fine and I had no issues with it, until I took the trcuk apart years later. Make sure the pressure works with your carb, or else you'll get flooding and starting issues.

I called Holley tech the carb and pump are both Holley the tech said it should be a good match . I can always add a regulator truck has a vented cap on it already

[54blackhornet]

The return line is to eliminate fuel deadheading at the carb, it’s not an emission control device. I would keep it in place myself over just plugging the lines. GM engineers knew their stuff.

[RichardJ]

Add a Pressure Regulator with by-pass. Adjust the pressure and have the by-pass return.

HLY-12-881 should work.

https://www.summitracing.com/parts/h...SABEgKkQ_D_BwE

[Impact02]

I have a 96 mercury marine 454 with a 750 double pumper in my 72. I am only running the feed line no return line and do not have any vapor lock issues even in the hot summer. You should be fine.