scottylack
Well-Known Member
looking for a good Walbro for my 360/4bbl engine...any suggestions? Not sure if the high pressure ones are just made for EFI ?? thanks
WALBRO Pump for Carbureted System??
- Thread starter scottylack
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mopardude318
Well-Known Member
the walbro gsl 392 seems the be the favorite..
scottylack
Well-Known Member
Is that too much pressure?
moparlover
Well-Known Member
i dont think the brand or psi of the pump matters as much as the setup.
clean or new tank, supply and return lines with bypass regulator before the carb
pre pump filter (coarse 100 micron) post pump filter ( finer around 40 micron)
you choose pumps not by psi but by gallons per hour... horsepower * .5 divided by 6.2
so 400hp you need 33 gph
500hp you need 40 gph 6an supply and return lines 3/8"
600hp you need 50 gph 8an supply and return lines 1/2"
etc
you could call aeromotive or walboro or one of the others and one of their techs will help you get the right model pump & regulator for your needs.
http://aeromotiveinc.com/tech-help/frequently-asked-questions/faq-carbureted-regulators/
clean or new tank, supply and return lines with bypass regulator before the carb
pre pump filter (coarse 100 micron) post pump filter ( finer around 40 micron)
you choose pumps not by psi but by gallons per hour... horsepower * .5 divided by 6.2
so 400hp you need 33 gph
500hp you need 40 gph 6an supply and return lines 3/8"
600hp you need 50 gph 8an supply and return lines 1/2"
etc
you could call aeromotive or walboro or one of the others and one of their techs will help you get the right model pump & regulator for your needs.
http://aeromotiveinc.com/tech-help/frequently-asked-questions/faq-carbureted-regulators/
magnumdust
Well-Known Member
What i read online is that you need to run a bypass regular and run a larger return than your feed. So like a An6 feed and an an8 return.
Good advice.
We run a Walbro 392 pump on our turbocharged slant six, with Holley double-pumper 600 4-bbl and have ZERO problems using an Aeromotive regulator that adjusts the pressure down to 6psi with no boost, which the carburetor likes. The regulator has a 3/8" supply with a half-inch return, and that setup provides a steady 6-psi gauge reading, for the gas coming out of the regulator under all circumstances.
The secret to running a high-pressure pump is the regulator and the return line. We didn't get satisfactory results until we increased the return line from 3/8 to 1/2"... Don't ask me why; I can't answer that... I just know it worked.
Here's a photo...
hey bill do you think a 1/2 in feed and a 1/2 in return will work this is what im trying to do now with the 392 pump.
I can't see why that wouldn't work, but consider this: With 60psi pressure from the pump, why would you need a half-inch supply line? That is an AWFUL lot of gasoline (at 60 psi, I mean.) I can't imagine that a 3/8-line would be too small...
Food for thought...:coffee2:
I agree bill the 1/2 line was already there on the car and the fuel sending unit was already 1/2 so I just decided the easyiest way would just put a 1/2 return nipple in the sending unit and run a line thanks.
Since the hardware is already there, that makes all kinds of sense. I'd try it.... I think it would probably work okay.
scottylack
Well-Known Member
thanks for your help...going to go with the Walbro 392, an Aeromotive bypass boost referenced regulator and a 1/2 return line!
keep us informed and a few pics of your setup good luck and thanks
BillGrissom
Well-Known Member
A carbureted engine usually doesn't usually need the biggest, baddest EFI pump. Even a little pump will flow a lot of volume at 10 psi outlet. Walbro has flow curves. 1/2" lines sounds like overkill. I currently have a Walbro (190 lph?) on my 65 Dart w/ a carb. I have a 3/8" supply and 5/16" return. With no bypass regulator, it runs ~10 psi on the return. That is too much for a carb needle to handle, so I use an in-line Holley regulator (pressure-reducing, came w/ a blue pump) to reduce to ~5 psi at the carb. The EFI pump is for future FI.
I expect the 10 psi return is due to returning thru the 1/4" vent tube in the sender I used. Whatever your design, you might need to install some pressure gages, at least temporary, to tell what is going on.
I expect the 10 psi return is due to returning thru the 1/4" vent tube in the sender I used. Whatever your design, you might need to install some pressure gages, at least temporary, to tell what is going on.
magnumdust
Well-Known Member
But the idea behind the larger 1/2" return is to compensate for the pump. Again from things i read, if you're return isnt big enough to compensate, you will have pressure creep.
scottylack
Well-Known Member
Thanks for the input. My ride is supercharged so I will be using a boost referenced regulator
on a N A engine and using the 13204 bypass regulator do you just plug the boost nipple?
I don't think it needs to be plugged, but that's not a bad idea, to keep stuff out of it...
scottylack
Well-Known Member
what about the ignition set up? Anybody want to elaborate on a good system for a Paxton motor?
UOP
Well-Known Member
I know it's not exactly the same (in-tank vs rail mount) but you can run a pump intended for efi with a carb no problem. The pump in my car is a Walbro 255lph (forgot the p# but it's the "high pressure" one turbo imports use) and the setup is 3/8" (-6 AN) feed/return lines with the regulator mounted on the end of the fuel rail, past the carb, just like efi.
As for the ignition, take a look at MSD's programmable digital 6. You lock the distributor on 0 degrees, then just program initial and total timing, curve, retard, etc with a laptop. Much easier to set up than dealing with distributor springs and advance slots.
[ame="http://www.amazon.com/MSD-Ignition-6530-Programmable-6AL/dp/B001O22NVM"]Amazon.com: MSD Ignition 6530 Programmable 6AL Ignition Box: Automotive[/ame]
Pic of fuel rail and regulator to show what I'm talking about.
As for the ignition, take a look at MSD's programmable digital 6. You lock the distributor on 0 degrees, then just program initial and total timing, curve, retard, etc with a laptop. Much easier to set up than dealing with distributor springs and advance slots.
[ame="http://www.amazon.com/MSD-Ignition-6530-Programmable-6AL/dp/B001O22NVM"]Amazon.com: MSD Ignition 6530 Programmable 6AL Ignition Box: Automotive[/ame]
Pic of fuel rail and regulator to show what I'm talking about.
Mad Dart
Nothing to see Here!
Looks good! Is the fuel pressure rock solid like that? Did you have it a different way before?
If so what was the difference between the 2 configurations?
If so what was the difference between the 2 configurations?
UOP
Well-Known Member
Yup, fuel pressure is rock solid. I used to have it mounted before the carb ( fuel pump to the fuel pressure regulator (FPR), then "Tee'd" off to the carb, with return), but found that I was having some percolation issues in the line between the FPR and carb that caused irregular fuel pressures. My engine bay gets VERY hot, and the problem was exagerated by the fact that the FPR was located so far away from the carb (inner fender, firewall mount is not nhra legal) so the line going from the FPR to the carb was over 3 feet long. Even though cool fuel was constantly flowing through the FPR the fuel inside the feed line was stagnate, which allowed it to get too hot. I tried several things to relieve the problem, including insulating the line, but nothing helped.
Earlier this year I stumbled on a thread on Yellowbullet about FPR locations that prompted me to research the idea more. Turns out that mounting the regulator after the carb has a few benefits over fender well mounting. The one benefit that caught my eye was that the carb would now get a cool fresh supply of fuel since all of the fuel sent by the pump is now sent straight through the fuel rail first, then to the FPR. It's just like an efi system. What this does is ensure that the float bowls are supplied with the freshest fuel possible, and that the bowls are filled first without having to pass through the FPR first, eliminating a possible restriction.
For me it was problem solved, no more issues. Glad too since I bracket race a lot and am always chasing consistency. Any more questions feel free to ask.
Earlier this year I stumbled on a thread on Yellowbullet about FPR locations that prompted me to research the idea more. Turns out that mounting the regulator after the carb has a few benefits over fender well mounting. The one benefit that caught my eye was that the carb would now get a cool fresh supply of fuel since all of the fuel sent by the pump is now sent straight through the fuel rail first, then to the FPR. It's just like an efi system. What this does is ensure that the float bowls are supplied with the freshest fuel possible, and that the bowls are filled first without having to pass through the FPR first, eliminating a possible restriction.
For me it was problem solved, no more issues. Glad too since I bracket race a lot and am always chasing consistency. Any more questions feel free to ask.
Mad Dart
Nothing to see Here!
I am running the Walbro GSL-392 pump with the FPR mounted on the inner fender as usual and set up like yours use to be using -8 feed and -8 return. I was having issues too where the FP will be high and after the car warms up it would drop a bit. I have been chasing my tail on it like you did. Recently I put a restrictor in the return line and that seemed to help but then again after it was running a while and got hot it returned back to the same issue, not as bad but still there. When I get back out in the garage I will be setting it up just like yours is.
Did your FP start high and drop or did it do the opposite and spike? What exactly was your issue with the FP?
I also heard that Liquid filled gauges can sometimes give a false reading when they get hot? Have you heard this before? Do you run a liquid filled or just a regular? Any input on the subject will be appreciated.
UOP
Well-Known Member
Sounds like your problem is different than mine. Fuel pressure was all over the place when it got hot in the engine bay. If you're just seeing a higher reading at warm temps it may be your gauge, as long as it's a consistent rise. Liquid filled gauges are well known for showing false readings at different temps but I do think it's possible for non liquid filled gauges to be affected by heat as well. Things expand when heated, it's just the way things work. I'm not saying you shouldn't change your setup but I would try something first. When you get back from a drive, wrap the gauge with a cold wet towel to see if the temp goes back to where it needs to be. I'm thinking that it's possible the pressure is staying the same and the gauge is giving a false reading. Just something that came to mind.
As for the gauge itself, I personally run a non liquid filled NOS brand gauge. The gauge in the pic shown above is a Summit brand and turned out to be just fine, but I figure a gauge intended for a nitrous application would be a good bet.
As for the gauge itself, I personally run a non liquid filled NOS brand gauge. The gauge in the pic shown above is a Summit brand and turned out to be just fine, but I figure a gauge intended for a nitrous application would be a good bet.
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