Recommended fuel line sizes to support NA 575 HP
 

I am re-plumbing my fuel system and switching to a Holley 6-valve mechanical pump. I planning to replace the small 3/8" tank pickup with a 1/2 inch pickup, and I think I have room to install a pipe nipple on the pickup and a sweeping 90* fitting instead of the right angle rig that is on there now. From there my plan it to go with 1/2" hose up the the fuel/water seperator/filter. I bought one that has the larger 1/2" in/out fittings. From the filter, #8 braided line with AN fittings to the input side of the pump. My question concerns the line from the pump output up to the carb. Will my current #6 braided line flow enough fuel? This engine has an 800 Holley and will see a max of 5300 RPM.

One more question - since I am eliminating the anti-siphon valve at the tank, do I need to install some type of shutoff valve? Any recommendations for this?

Thanks!

Yes install a shutoff, I think -6 will be fine. I quickly calc'd that to be about 1gpm flow.

.6#fuel/hr/hp is the formula I used

Would something like this work OK for a fuel shutoff valve?

http://www.downwindmarine.com/images/P/91002632.jpg

http://www.downwindmarine.com/Apollo...-91002632.html

The -6 carb lines should not originate by a -6 that then Y's. A -8 that Y's into 2 6's shall be fine.

-10 pickup and line to mechanical pump. -8 to carb distribution block. 2 x -6 to carb.


Most carb lines come with a Y or distribution block same size as lines going into carb, thus why you see many people run a -8 set up to carb.

SB, I will have to measure the diameter of the bung in the fuel tank. I'm not sure if it is large enough in diameter to support a 5/8" diameter tube and fitting. I think 1/2" is about the max, which would correspond to a -8 AN.

1/2" shall prove totally fine. As always, just don't put some stupid fitting in there that kills flow.

Budman, I have fuel shutoff valves like that in my boat. They work.

Thus my plan for a pipe nipple to allow me to install a 90* sweep fitting instead of the right angle. The one on there now actually has part of the opening obstructed by the threads of the barb fitting that is screwed into it. It's hard to see how it could flow much of anything at all. No wonder my fuel pressure gauge was fluttering.

Anybody have suggestions on what type of hose to use going from the tank pickup to the fuel filter? I know I could go stainless braided with AN fittings, but that shizit is getting expensive. Is there something similar to the push-loc that is safe to use but less expensive? Hell, the damned thing had USCG approved rubber 3/8 hose on it for 30 years with no problems.

Bud, try Sniper fittings. Cheapest I've found and much nicer quality than most. You can order directly from their website...