Fuel Pump for Sniper QuadraJet Question

[LKLusza]

Hi Folks.

1. I have a 1970 Pontiac GTO with the standard 350 HP 400 engine.
2. I'm preparing to install the Sniper QuadraJet EFI (550-867).
3. For fuel delivery, I've chosen the in-tank pump with regulator and integrated return for GM A-Bodies (12-303). The intention is to have the pump feed the EFI using the single factory hard-line in a "dead head" configuration.
4. The Sniper QuadraJet all specify 3/8" minimum fuel plumbing to feed the EFI.
5. The factory Pontiac fuel hard line necks down from 3/8" to 5/16" at the end of the tube to be connected to the gas tank. Forward from that, it's 3/8" tubing all the way forward through the factory mechanical pump and on up to the carb. I know it sounds odd and I don't know why Pontiac went that route, but they managed to adequately feed their Ram Air III and IV as well as the 455 HO engines with this arrangement.
6. I observed that the fuel feed tube from the 12-303 pump also happens to neck down from 3/8" to 5/16" at the end. Interestingly, checking in the replacement parts list, the Holley pump used in the 12-303 shows that it has a 5/16" output port that steps up to 3/8" prior to the regulator section of the assembly.

So my question is this: Given that the 12-303 pump is rated for for 255 LPH and regulated @ 58 psi as is, do I have to remove the 5/16" sections of the 12-303 feed and factory hard-line ends (ensuring it's 3/8" all the way through) to make the QuadraJet EFI happy or can I leave the 5/16" sections as is?

Sorry for the long winded preface, but I just discovered this and wanted to see what you all thought before potentially having to alter an expensive 12-303 fuel pump. Thanks, Larry

[Danny Cabral]

You'll be fine at 350 HP and 58 psi fuel pressure.

[63 bomb ohc]

That's the exact setup I used and it works great. I will caution you on one thing though: Running a true dead-head setup with the QuadraJet Sniper, you'll need a fuel damper at the throttle body. See this post for more info: https://forums.holley.com/showthread...ight=quadrajet. This is the damper I ended up using and it solved a lot of issues: http://www.radiumauto.com/Fuel-Pulse...Kits-P751.aspx

[LKLusza]

Thank you both for the quick replies!
63 bomb: Looking at the pictures in your other post, I see the damper is mounted inline with the fuel feed prior to the TBI unit. Being a true dead head setup, do you think it'd still work if attached to any of the other three available ports besides the one used for the actual fuel inlet? My thought is that since all ports see the same pressure, it ought not to matter. I'm just trying to hide things visually as much as possible to maintain a "stock" appearance. Thanks again. Larry

[63 bomb ohc]

It shouldn't matter where it goes, as long as it's as close to the throttle body as possible. An email to Radium might not bad idea just to be on the safe side.

[LKLusza]

Will do. Thank you for your help! Larry

[LKLusza]

Hi Folks. Just reporting back with some results. First, a big hat tip to Danny Cabral for the fuel pump advice, and 63 bomb ohc for the heads up about using a fuel damper with a dead head system and hard lines. I had to fab a bracket to mount the Radium fuel pressure damper. It all turned out well and works awesomely. The gauge needle is rock steady @ 60 psi and the car runs great. And it all hides under a standard Pontiac dual snorkel air cleaner assembly too. Thanks again!

[63 bomb ohc]

Man! Looks absolutely awesome! Congrats on the install and happy driving.

[Cutty70]

With that pump, do you hear it prime every time key is cycled?

[LKLusza]

Yep. You'll hear the pump priming, followed by a fairly distinct "click" sound. Once you hear that, you can crank the engine.