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EFI back to Carby


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#1 Marks LXTorana

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Posted 16 July 2017 - 10:25 AM

Hi all,

I have recently had my 304 rebuilt and converted it and the engine bay back to carbie (Holley double pumper). I still have the high pressure fuel pump(s) in the car and wondering what the best and easiest set up would be? I initially bought a regulator with a return to the tank although the pumps continue to pump all the time with this set up and I noticed as soon as I started cranking that the pressure in the line at the carbie dropped from 5psi to almost nothing, so I assume the return is taking all the pressure away.

Is there a suitable pump that deletes the need for a regulator?



#2 purrlx

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Posted 16 July 2017 - 03:43 PM

A bit old school but i used holley blue pump back in the day with the regulator that came came with it. Probably better pumps around now.



#3 LC-GTR-1969

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Posted 16 July 2017 - 06:08 PM

I run a holley blue- excellent pump and very straight forward- highly recommend as long as you can tolerate the pump noise- its actually really bad, they make a racket...

 

No prob in my car- once the engine has fired I cannot hear anything but the induction and exhaust noise



#4 Redslur

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Posted 16 July 2017 - 06:50 PM

And even more basic is a Holley Red where you don't even need a regulator.



#5 ozyozyozy

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Posted 16 July 2017 - 10:43 PM

Carter black, there are 2 types, 7psi and 15 psi.
You prob get away without a reg with 7psi but for safety on your carb i would go the 15psi and a reg.
They are quieter than the holleys.

As for regs ots hard to say what to use without knowing how you have plumbed the system eg at what point is your return line, engine bay or at back of the car.
A diaphragm style reg is more stable with fuel pressure.

Aeromotive do regs to run efi pumps to carby.

Sounds like you may have a plumbing issue if its just dumping all pressure to tank or a dodgey reg.

#6 gtrboyy

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Posted 17 July 2017 - 02:06 AM

Carters are nice & quiet.

 

I had a holley black in boot with thick rubber mounts that you could just hear at idle...return line would have made it quieter.



#7 Marks LXTorana

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Posted 17 July 2017 - 12:26 PM

Thanks for the feedback so far. I have been looking around to understand my easiest solution. At the moment, I have an in-tank pump (dont know if it is high or low pressure), directing fuel to a high pressure in-line pump sitting on the outside of the tank, with a filter. The fuel original was directed to the fuel rack and then returned to the tank via a separate 5/16 line to the tank.

My preference is to replace all that with a single in-tank low pressure pump, direct to the Holley carby, This eliminates the second pump, the return line and any need for a regulator. Does this sound feasible? I just need to find the most appropriate in-tank pump to use.



#8 arrimar

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Posted 17 July 2017 - 06:54 PM

Simplest solution is mechanical isnt it?

#9 ozyozyozy

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Posted 17 July 2017 - 07:52 PM

You could prob make that work, not sure if you can get low pressure in tank pumps that have the flow rating.
Is the engine modified or standard?

Using a return line vs not using, will always get conficting info, think if your making good power and have a big fuel supply setup, a return line somewhere in the system is required.
Stock to light modified can get away without a return.
Me personally i would use some type of regulator either way, creates a head of fuel to help the carb to not starve when accelerating hard.

#10 Marks LXTorana

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Posted 17 July 2017 - 10:36 PM

Simplest solution is mechanical isnt it?

Do the 304 blocks take a mechanical pump? If so, do I just replace the in-tank pump with a fuel line to the bottom of the fuel tank?



#11 Marks LXTorana

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Posted 17 July 2017 - 10:45 PM

You could prob make that work, not sure if you can get low pressure in tank pumps that have the flow rating.
Is the engine modified or standard?

Using a return line vs not using, will always get conficting info, think if your making good power and have a big fuel supply setup, a return line somewhere in the system is required.
Stock to light modified can get away without a return.
Me personally i would use some type of regulator either way, creates a head of fuel to help the carb to not starve when accelerating hard.

 

It is a fairly angry street engine with stage 4 cam, flat top pistons, VN heads with roller rockers, Edelbrock air gap dual plane and Holley 700 double pumper. I am conscious of keeping the flow rate up to avoid leaning out the engine. I thought the Aeroflow regulator with the original pumps might have addressed this, although as stated, the pressure seems to drop as soon as I start cranking the engine. I did read somewhere on another forum that oil filled pressure gauges can fluctuate significantly although I thought it was due to heating up.....

 

I have the receipt for the in tank pump I bought from AFI in Granville in 2013. Code number FP0954 doesn't tell me much although I am guessing it is a high pressure unit.



#12 gtrboyy

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Posted 17 July 2017 - 10:48 PM

Carter or holley + regulator is all you really need outside tank as long as it has decent pickup line & filters. Any decent electrical f/pump will recommend regulator even if it's fixed at 4.5psi If you have already got a return line may as well use it. Regulator should be holding pressure not dropping it with excess fuel returning to tank instead of overloading f/pump & heating fuel. When you turn it off does it hold 5psi on guage? What are engine/driveline specs?

#13 ozyozyozy

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Posted 17 July 2017 - 11:48 PM

Sorry stage 4 cam doesnt mean shit to me, need actual specs and comp ratio.
If its got/needs a 700 holley then its obviously pretty heathly engine.

Would def recommend something like a carter 15psi pump and a reg to bring it down to about 7psi for carb.

Its not cutting the power to the fuel pump when cranking is it?

The pressure fluctuation on those guages can also be caused by the type of regs used, the needle and seat type regs would be constantly opening and closing to keep pressure at carb due to the carb needle and seat.
A diaphgam style reg has much more stable pressure.

Need to google some plumbing diagrams, beware not all regs are plumbed the same so finding what your reg is suppose to have.
Bypass regs are plumbed very different but keep good pressure and volume at the rail/carby, maybe you bought one of these and is incorrectly plumbed, easy to do.

#14 Marks LXTorana

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Posted 18 July 2017 - 10:32 AM

Sorry stage 4 cam doesnt mean shit to me, need actual specs and comp ratio.
If its got/needs a 700 holley then its obviously pretty heathly engine.

Would def recommend something like a carter 15psi pump and a reg to bring it down to about 7psi for carb.

Its not cutting the power to the fuel pump when cranking is it?

The pressure fluctuation on those guages can also be caused by the type of regs used, the needle and seat type regs would be constantly opening and closing to keep pressure at carb due to the carb needle and seat.
A diaphgam style reg has much more stable pressure.

Need to google some plumbing diagrams, beware not all regs are plumbed the same so finding what your reg is suppose to have.
Bypass regs are plumbed very different but keep good pressure and volume at the rail/carby, maybe you bought one of these and is incorrectly plumbed, easy to do.

Excellent point! I didn't check the power supply at cranking although there is a very good chance it is wired so that the pump cuts out, which will explain the drop in pressure!

The compression is 10:1 (possibly 10.1:1) although I need to get the cam part number off the box to give the detailed specs.

I will check the power to the pump at cranking and this will eliminate one concern, which means I could keep the current set up and save some time and money.



#15 mick_in_oz

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Posted 18 July 2017 - 09:24 PM

The fuel set up you currently have is prolly the best approach!

 

All you need is a suitable low pressure bypass reg up near the carb, the efi pump will like working with the lower pressure, it will pump more, work less, run quieter and last longer.

 

EFI pumps do NOT like or tolerate a dead head reg, it needs to be a bypass reg., typically they are a roller cell design or perhaps a gerotor and are a positive displacement pump, and seldom have any internal bypass system.

 

Go put a Holley Red or Blue on if you like noise and want to be broken down here and there and buying the occasional replacement pump...

 

As mentioned above, it could be wired such that the pump isn't powered at certain times, but why does it matter if there is no pressure while cranking, its prolly a good idea, a Holley carb will run for some time on what is just in the bowl, so will be plenty there once the pump is back in action when the key is in the run position. Another plus will be less load on the battery while cranking the engine.

 

If the fuel pumps that are there are neat and quality it would be a huge waste to throw them away just because there is a minor issue or someone doesn't understand the install properly.

 

LOTS of big HP cars (both efi and carbed) run EFI pumps, lift pumps and swirl pots, bypass fuel systems, its an ideal configuration.

 

Another benefit of having a bypass system with the reg at the carb/front is that as the car accelerates hard there are G's created that load the pump more, the fuel in the line may generate another psi or two that the fuel system has to account for, with a reg at the back this cant happen, but a bypass system, using a pump capable of more pressure than is needed, the bypass reg will account for the additional pressure to counteract the acceleration G's, so your gauge will show a constant pressure even under start line G's.

 

Just my two cents.

 

If you can't help yourself and pull the efi pumps out, at the very least use the Carter pumps mentioned above, at least then it'll be quiet and reliable.



#16 Marks LXTorana

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Posted 18 July 2017 - 09:39 PM

OK, problem solved! 

ozyozyozy was on the money, the pumps were cutting out when cranking so that explained the pressure drop. It holds a good constant pressure otherwise so all good in that respect. The fuel pumps are a little noisy although I started it for the first time and I wont need to worry about the pump noise! Damn that thing is loud  :rockon: ​. The cam is a Crane 884401 which if you look up the specs is a wild cam suited for 3000-6500rpm range. I only ran it for about 10 seconds as I need to break in the cam/lifters ect and there is a noisy roller rocker which needs tightening (and I didn't want the neighbours calling the cops while I run it in for 20 minutes @ 2000rpm.....). Oil pressure was good so I think I am all set!



#17 ozyozyozy

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Posted 19 July 2017 - 11:13 PM

👍🏽👍🏽
Good work.
Dont be too stressed prob will have a couple of teething issues to sort.
I wouldnt say the cam is huge, on the aggresive side for a hydraulic cam and street use.
Take care setting the rockers double check if need be, there is a preload amount to set them to, i cant remember what it is for them, been a long time.

#18 Marks LXTorana

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Posted 20 July 2017 - 10:28 PM

From Crane Cams:

 

How do I Adjust Hydraulic Lifters for Proper Preload?
In order to adjust the preload the lifter must be properly located on the base circle or "Heel" of the lobe. At this position the valve is closed and there is no lift taking place. You will need to watch the movement of the valves to determine which lifter is properly positioned for adjusting.

1. Remove the valve covers, and pick a cylinder you are going to set the preload on.

2. Hand rotate the engine in its normal direction of rotation and watch the exhaust valve on that particular cylinder. When the exhaust valve begins to open, stop and adjust that cylinder's intake rocker arm. (Why? Because when the exhaust valve is just beginning to open, the intake lifter will be on the base circle of the lobe, the correct position for adjusting the intake.)

3. Back off the intake rocker arm adjuster and remove any tension from the pushrod. Wait a minute or two for that hydraulic lifter to return to a neutral position. The spring inside the lifter will move the pushrod seat up against the retaining lock if you give it time to do so. (If you are installing brand new lifters they will be in the neutral position when they come in the box.)

4. Now spin the intake pushrod with your fingers while tightening down the rocker arm. When you feel a slight resistance to the turning of the pushrod, you are at "Zero Lash". Turn the adjusting nut down one half to one full turn from that point. Lock the adjuster into position. The intake is now adjusted properly.

5. Continue to hand turn the engine, watching that same intake. It will go to full open and then begin to close. When it is almost closed, stop and adjust the exhaust rocker arm on that particular cylinder. (Again, when we see the intake almost closed, we are sure that exhaust lifter is on the base circle of the lobe.) Loosen the exhaust rocker arm and follow the same procedure described before in steps 3 and 4 to adjust this rocker arm.

6. Both valves on this cylinder are now adjusted, and you can move on to your next cylinder and follow the same procedure again.





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