bluethunder364

iTrader: (5)

Having some fuel flow issues so went from 3/8" line to 1/2"line .Currently running a CARTER 4601 Pump . suppose to generate 14-16 psi/100gph. Also have a Holley regulator. Now that I have 1/2" line , I have very little fuel pressure 3-4 pounds. Do i need a higher output pump now? Holley tech says i need to restrict the flow some place to bring up the pressure.??? don't really want to restrict it. Any thoughts from the drag racers??. Would thought that the carter pump would keep up.........maybe bad pump???

Thanks

Pop N Wood

iTrader: (1)

Is this a dead head or return style regulator? If return did you upgrade both the supply and return?

Any adjustment available on the regulator?

GC99TA

iTrader: (30)

What were your prior fuel flow issues that prompted the upgrade to the 1/2 inch line? Not enough fuel being delivered for your power level or was it low on pressure through the 3/8 line as well?

Remember that pumps are rated at a volume of fuel they can move. If your Carter is rated at 100gph, the 14-16psi cited by the manufacturer is probably based on a certain line size; most likely 3/8 line in this case. The actual pressure produced comes from trying to push a certain volume of fuel through a restriction (line size). The more volume a pump is capable of moving, the higher the pressure will be for a given line size. The pressure drop you saw was most likey due to the larger line size you changed to.

Let us know what problem you were originally having before swapping lines and how old your pump is. It may just be that your pump isn't performing as advertised. Or as stated above, maybe just a mis-adjustment of your regulator? I would also check that the pump is grounded well and is receiving adequate voltage at all times.

bluethunder364

iTrader: (5)

Thanks for the replies.... I 'm pretty sure that the pump can't keep up with the demand. At the end of the 1/4 mile I am getting some indication that not enough fuel is there. (skipping) As soon as I let off it comes back. I had this pump back in the car when I was running a SBC 350 with alot less HP than my ls is making now, never changed the pump. I made some other changes, put a 1/2 bung to pull from the bottom of the tank rather than from over the top of the tank. So from what I have read and have been told for the HP that the car has I should be running 1/2" line. Also have a reguator but no return line. The pump may be the issue now as I have only 3psi at the regulator after a couple of adjustments. The brake specific fuel consumption calculation says I need a pump with 120/130 GPH. If that is so it would leave my current pump out of the running sort of speakin @ 100GPH with 3/8 " line. I tried running fuel from the line coming into the regulator into a gas can and if the pump should run 100GPH it should pump about 1.6 gallons into the can in 1 minute. No way that happened. So wondering if the pump is tired and the larger 1/2" line is to much for it. I need to try a larger GPH pump. I think it will fix th problem but not sure which pump to get. Like the new Holley 12-125. Has a built in reg. to 7PSI and flows 125GPH. Not sure what else could be wrong. Thanks

GC99TA

iTrader: (30)

Sounds like this is the case. I'll bet the pump is slightly undersized for the demand even when operating to full capacity and is probably tired to boot.

Maybe look into the Aeromotive SS pump. I've got a few buddies that have had good luck with it. http://aeromotiveinc.com/products-pa...l-pump-38-npt/ At 140GPH, it would be just about right for what you're trying to do. Looks like they rate it at 14psi through a 1/2 inch feed line and it can be used a bypass or deadhead regulator. Just one of probably many options.

bluethunder364

iTrader: (5)

Thanks fo the help. Really appreciate it. I'll keep ya posted. Will order a new pump. I like the Aeromotive, but the inlet -oulet don't match up to my lines. Would have to reroute everything.....pain. May try a mallory 140

GC99TA

iTrader: (30)

No problem.....I hope it works out for you. For what its worth, I've heard not so good things about the Mallory pump around here and there's lots of good feedback in this section on the Aeromotive SS pump. Also, the Aeromotive has a 3/8NPT inlet on one side of the pump base and a 3/8NPT outlet on the opposite side, which is a pretty standard configuration. It may look like both ports are on one side, but that second position on the inlet side is the outlet pressure screw, not the outlet port itself. I don't know if that's what you were thinking about the configuration being different or not. http://aeromotiveinc.com/wp-content/...9/12/11203.pdf

Either way, I don't own stock in the company or anything....LOL...I just don't want to see you buy another pump that you're unhappy with. I just remember seeing a post where one member was so angry at his second Mallory 140 failure that he literally set it on fire. I think it was 1970camaroRS. Best of luck with whatever pump you end up with.

EDIT: Here's the thread I was thinking of: https://ls1tech.com/forums/carburete...mendation.html

Pop N Wood

iTrader: (1)

I assume you are measuring the pressure at the carb and not the pump, so no way is a larger fuel line going to cause a loss of pressure from too much flow. If anything the larger line should increase the pressure because there will be less pressure loss leading up to the gauge.

Sounds like either your pump or your regulator is going bad.

dr.dub

I just installed that aero pump, return system on 3/8 line, thing hit well one 20 first time I fired up. 3/8 return line is to small having problems dialing fuel pressure in ATM. Bit noisy when solid mounted but looks nice and works.

bluethunder364

iTrader: (5)

What is the part # for the Aeromotive SS pump?? Thanks

Pop N Wood

iTrader: (1)

you realize there is no way that is possible, right? your pump may be tired but the larger line will make it work less, not harder.

GC99TA

iTrader: (30)

The part number is in the links I provided above - its 11203.


I'm not sure I follow everything your saying. I'm not trying to sharp shoot you by questioning you. There may be something that I'm missing here and want to hear your perspective to be sure I'm thinking clearly.

Having said that, I fully agree with you that the larger line would make the pump work less and the smaller line would make it work harder. It's just like high blood pressure; your heart pumps a fixed volume of blood and the size of your veins dictates how high your blood pressure is. When internal vein size is reduced, blood pressure increases and your heart (pump) works harder to push the same volume of blood through a smaller line. However, it also sounds like you're saying that the larger line should not decrease the overall flowing fuel pressure, and that's where I don't follow you.

I think the key here is whether or not the line is flowing when the pressure reading is being taken, or if its being measured with the engine is off, bowls full, and needle valve closed. I agree that the same pump will eventually cause the same amount of pressure in the line (regardless of line size) if the line is not flowing and has been stopped by a closed valve.

But if we're talking about flowing pressures, this is the way I see it: If the pump is moving X amount of fuel volume (say 100gph) through a very large line (lets say 5/8 line for an extreme example) and another identical pump is moving (or attempting to move) the same amount of fuel through a 1/4 inch line, the smaller line is going to cause more restriction. In turn, this restricion is going to cause more pressure in the line and sacrifice volume.

It's like if I have water flowing through an open ended garden hose. It will move a fixed large of volume of water but at a low pressure. However, if I partially cover the end of the hose with my thumb, I cause a restriction in the line by creating a smaller opening. This smaller opening is still attempting to pass the same volume of water but cant, so the line pressure increases as water is "backed up" in the hose. This pressure increase would be even greater if the entire hose size was reduced instead of just the opening. This of course assumes that the volume of water attempting to be pushed through the hose hasn't changed and has remained a constant.

So maybe you're talking non-flowing pressure where I'm talking flowing pressure? Or maybe I've just completely missed something here, which is entirely possible. I don't mean to hijack the OP's thread but want to see what it is that I'm not understanding.

bluethunder364

iTrader: (5)

Thanks for the link......yeah I missed it when I first looked at it. I just ordered the #11203. Will be here Fri. I'll give you a follow up after the install. Thanks for the explanation above . You are correct. Mr Pop N Wood I never said the bigger line was going to make the pump work harder, I said I thought it just couldn't keep up with the volume cause the pump had a low GPH rating and was pretty old. Went back and check on when I got it. Long time ago, plus it was used!! I was asking it to do to much. Thanks again

bluethunder364

iTrader: (5)

UPDATE...
New #11203 in!! All new line front to back, and I have great fuel pressure. Will road test today and track soon as I can get there. Will post update again. Thanks

GC99TA

iTrader: (30)

Cool.....glad to hear it.