Fuel system. - Chevelle Tech
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post #1 of 26 (permalink) Old Feb 15th, 20, 7:25 PM Thread Starter
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Fuel system.

Hey guys was doing a little testing this week. I recently installed an Edelbrock mechanical fuel pump and decided to do a little testing. So the system is a static and the fuel pressure after the reg is bouncing from 5.75-6.05 constantly at idle. 950rpm. Did a pull and from a dig fuel pressure drops to 2.75 at 6800rpm 1st gear and 3.15 at 6800 rpm 2nd gear. 3/8 from tank to pump. -6 from pump to reg. -6 from reg to log on carb. Tested with my gauge I use at work “plumber” to test static and flowing pressures. Works on liquid and vapor. Basically very accurate. So, I have a new holly 12-454-40 pump that was recommended. This is my idea for a new set up. What do those with experience think. 3/8 from tank to pump. -10 from pump to fuel catch can top. -10 from fuel catch can bottom to reg. -10 from reg to -10 log. Any recommendations on running the holly mechanical pump. Trying to avoid a dynamic system unless absolutely necessary
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post #2 of 26 (permalink) Old Feb 15th, 20, 7:48 PM
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Re: Fuel system.

Does the pump require a regulator? I would aim for 6-7 at idle and see what it does before ripping it apart. I ran a #10 hose in my car feeding 1000 hp. I also feel if itís got pressure there is gas in the bowl and itís fine. I think youíre going to do a lot of work for minimal gains.

Ray


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post #3 of 26 (permalink) Old Feb 15th, 20, 7:53 PM Thread Starter
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Thanks bracket. I’m trying to get a handle on the fuel as I have my direct port hooked up 250 shot and will start dialing that in as soon as I can get the fuel under control. I’d like to see 5.5-6.0 at 6800. The holly I’m about to install tomorrow puts out 11. And I’ll be regulating it down to 6.0 I think I’m having more of a volume issue hence my thinking of the catch can. Seeing less than 3 psi of fuel pressure certainly doesn’t make me want to push the 250 button. I’m basically holding my breath as is.
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post #4 of 26 (permalink) Old Feb 15th, 20, 9:17 PM
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Re: Fuel system.

I would not use a mechanical pump with nitrous...maybe 50hp shot.

'71 Malibu
3580 #, Carbed 6.0l LS swap in process
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post #5 of 26 (permalink) Old Feb 15th, 20, 9:32 PM
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Re: Fuel system.

With nitrous inadequate fuel can result in disaster. Why are you running nitrous? We all know it is cheeeep power but brings lots of possible problems. The solenoids should be replaced every other year IMO. If they fail you are in trouble. I like NA no power adder engines. Much more reliable and consistant.


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post #6 of 26 (permalink) Old Feb 15th, 20, 9:38 PM
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Re: Fuel system.

Good thing you checked before plumbing your nitrous and hitting the button. Snap crackle pop! Install a regulated electric fuel pump if you are going to run the bottle.

Your problem may be the pump, sucking air or the pickup sock in the tank. As soon as you put a demand on the pump it's not keeping up. It should easily hold 6psi through the rpm range.

I'm not familiar with that mechanical Holley pump. It probably shows fluctuations in pressure like any mechanical pump. I would run A Holley electric with 1 reg to the carb and one to the NOS system for consistent pressure and fuel delivery.
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post #7 of 26 (permalink) Old Feb 15th, 20, 11:04 PM
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Re: Fuel system.

Hi
If u have the correct fuel line size and pump should not be an issue.
Do u have the 110 gph or the 130gph [requires regulator] ????
flow /pressure chart should be available from Eldebrock , remember the 110/130gph is open flow . The flow at 6-7psi needs to match engine requirements .

Mechanical pumps fitted to engine donot like suction line restriction . This is why 1/2 line is recommended so often
Electric pumps fitted at tank are pushes and most can handle a little pressure drop
Most 3/ 8 line applications will work depending upon pump size eg electric units can easily over come pressure drop
Mechanical pumps like a more perfect install

engine required demand /flow
fuel line sizing
fuel pump chart flow vs pressure

All these answers and or calculators are on the net and or tech lines

** if total flow with nitrous is based of hp u maybe in trouble
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post #8 of 26 (permalink) Old Feb 15th, 20, 11:17 PM Thread Starter
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Thanks for the reply’s guys. I haven’t used the spray yet. I’m just being silly and want to go fast, spray is an easy way to do it. Iv slowly acquired most of the pieces to go twin turbo, but with my garage under construction 24x50x12 I’m probably not going to have the time to fab it up for this summer. The flow from tank to pump is good. I believe I’m having a volume issue. Do you think I should just bolt on the 12-454-40 dead head set up and run it on motor until I have the time to fab the turbo set up? And not risk the spray at all? I’m getting a lot of bad advise from a lot of local “racers” on using the spray. track isn’t open for a few months and I’m getting the itch so I find myself going in directions I normally wouldn’t go. Should I be aiming for a target psi at 6800? Or just not below a certain number. The car runs great as is, but after testing with my gauge and seeing below 3psi I’m worrying that I’m on the line.
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post #9 of 26 (permalink) Old Feb 15th, 20, 11:33 PM
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Re: Fuel system.

If you are going to spray 250 amd are dead set on the mechanical pump, I would set up a separate fuel setup for the nitrous. A small fuel cell, 803 regulator with a holley blue pump should work.

Nitrous is awesome, takes alot to get a clean tune though.
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'71 Malibu
3580 #, Carbed 6.0l LS swap in process
T-350, PTC 9" converter, 12 bolt, spool, 3.90 gears, MT ET R 275/60/15

355 [email protected]
125 [email protected]
388 Mud Motor- [email protected]
100 shot [email protected]
'72 Greenbrier Wagon: 454, 700R4, 12 bolt with 3.73
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post #10 of 26 (permalink) Old Feb 16th, 20, 8:02 AM
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Jeff
 
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Re: Fuel system.

I was having fuel issues with a 462 Pontiac with a Cliffs Quadrajet once. I sumped the tank and ran two 3/8" steel lines to a tee in the mechanical fuel pump. WOW!!! What a difference!! I was even able to go from 93 to 89 octane since the motor was 9.3:1, it would ping before the install..
I also have a 1/4" line for a return..

Before I did the dual 3/8" lines I was going to run one 1/2" which is the same as two 3/8 lines. A couple guys who know plumbing and how liquids flow told me it would be better to run two smaller 3/8" lines because the gasoline is being pulled under vacuum and not pushed. If pushed, the 1/2" would work better..

Last edited by hydro462; Feb 16th, 20 at 8:21 AM.
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post #11 of 26 (permalink) Old Feb 16th, 20, 8:16 AM Thread Starter
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Interesting I’m going to install the holly and dead head it. Then re do the test. If it’s still the same result I’ll be running two 1/2 Id lines from the tank and using 1 line for feed. When I eventually do the turbos I’ll use the other as a return with a Aeromotive belt drive fuel pump if the holly 40 won’t keep up. Thanks for the help guys. Today it’s swap the fuel pump and braze a small leak on heater core.
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post #12 of 26 (permalink) Old Feb 16th, 20, 8:49 AM
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Re: Fuel system.

Your pump is 225 gph. 1/2 line to pump and 8 to the bowls. Remember at 6 psi, flow is 1/2 advertised and then you have gravity working against you the faster you go. I used braided cloth covered hose and the slip together fasteners. Super easy. Cuts cleanly with a cable cutter. You can cut all pieces long, assemble, take it apart and make adjustments. Mine holds 6.5 psi at least an hour after shut off.


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post #13 of 26 (permalink) Old Feb 16th, 20, 10:19 AM Thread Starter
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Is that the push lock type? Sounds a lot better than my plan of hard pipe.
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post #14 of 26 (permalink) Old Feb 16th, 20, 12:18 PM
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Re: Fuel system.

Quote:
Originally Posted by 71malibuu View Post
Is that the push lock type? Sounds a lot better than my plan of hard pipe.
Super easy. If you make changes later, all the fittings are reusable.

This year I am going to add a fuel pressure gauge inside the car. I think I am running low on pressure about 300' from the 1/4 at the track. 1/8 mile is fine, I think ??? We will see.


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post #15 of 26 (permalink) Old Feb 18th, 20, 7:58 AM Thread Starter
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Installed the Holley, and 2x -8 lines from the reg to the bowls pressure is 6.5 at idle and 4.5 at 6800. All is well. Changes the oil and filter, drove the car for 45 min and now I have a very distinct tic under the valve cover. Solid roller so I’m used to some clicking, but this is different. Sounded like a belt chirping while idleing is park. Oil pressure is now 25-30 at idle vs 55 previously. And 50 under throttle vs 70-75 previously. At high rpm with load... doesn’t sound good. I’ll pull the valve covers after work today and pray it’s something stupid. Definitely starting to get nervous. Brand new engine with roughly 3k on it. Wish me luck. Pick up is welded. Using the same vr1 oil.
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