mopar head
Well-Known Member
Did you upgrade to at least 3/8 feed line?
Verify pump pushrod is still good?
Set reg. @ 6.5-7lbs
Verify pump pushrod is still good?
Set reg. @ 6.5-7lbs
Yes on all 3 accounts.Did you upgrade to at least 3/8 feed line?
Verify pump pushrod is still good?
Set reg. @ 6.5-7lbs
First post you say you dialed it down to 5.5lbsYes on all 3 accounts.
Yes 5.5 lbs...First post you say you dialed it down to 5.5lbs
It has a stock tank with 3/8 fuel line and, 1/4 return line, a Carter CRT6903 mechanical pump from the pump it has all -6 an steel braided lines to the Holley HLY-12-803 regulator then, -6 an steel braided line through an Earls filter to a Holley 850 double pumper. I really feel the regulator is the wrong one for this set up. The 1/4 return line has never been hooked under the hood and, this regulator does not support a return line. I'm hoping with the new regulator that is set up for a return line it will be able to vent some vapors from the heat under the hood and, keep the flow of fuel cooler to cut down on vapors.Ok fill us in on what components you currently are using. Fuel pump, carb, regulator etc. it seems you’ve covered a lot of bases already and all of us are picking at it. Tell us about the fuel system front to back.
Couple thoughts. I hate dead head regulators. They never seem to work perfectly and are constantly suspect. I would do as @pishta says and run it without the cap as a test. Then, get rid of the regulator completely and run the mechanical pump straight to the carb. That pump is rated at 7psi max so your 850dp needles and seats should be able to handle it if adjusted correctly. I’d like to see a pick of what Earls filter you’re using. Most of those have very little filtering surface area and are known to be problematic at higher hp levels. Also please let us know where you are measuring the fuel pressure and what you’re using. Remember pressure is resistance to flow so when the carb is dry and the pump is filling it, theoretically you’ll have zero pressure. Unless the pump is way oversized. Although you should never be able to run the bowls dry with a properly sized pump. Lastly 3/8” line IMO is just barely adequate for 600hp. I'd consider using the 3/8” for a return and stepping up the supply to 1/2” once the rest of the system is dialed.It has a stock tank with 3/8 fuel line and, 1/4 return line, a Carter CRT6903 mechanical pump from the pump it has all -6 an steel braided lines to the Holley HLY-12-803 regulator then, -6 an steel braided line through an Earls filter to a Holley 850 double pumper. I really feel the regulator is the wrong one for this set up. The 1/4 return line has never been hooked under the hood and, this regulator does not support a return line. I'm hoping with the new regulator that is set up for a return line it will be able to vent some vapors from the heat under the hood and, keep the flow of fuel cooler to cut down on vapors.
I'm measuring psi at carburetor with a non fluid filled gauge in the rail. It had a vented gas cap on it before and still had this issue. It also had this problem before the regulator was installed. Without the regulator this pump will put out 9.5 psi at the carburetor that was the point of the regulator.Couple thoughts. I hate dead head regulators. They never seem to work perfectly and are constantly suspect. I would do as @pishta says and run it without the cap as a test. Then, get rid of the regulator completely and run the mechanical pump straight to the carb. That pump is rated at 7psi max so your 850dp needles and seats should be able to handle it if adjusted correctly. I’d like to see a pick of what Earls filter you’re using. Most of those have very little filtering surface area and are known to be problematic at higher hp levels. Also please let us know where you are measuring the fuel pressure and what you’re using. Remember pressure is resistance to flow so when the carb is dry and the pump is filling it, theoretically you’ll have zero pressure. Unless the pump is way oversized. Although you should never be able to run the bowls dry with a properly sized pump. Lastly 3/8” line IMO is just barely adequate for 600hp. I'd consider using the 3/8” for a return and stepping up the supply to 1/2” once the rest of the system is dialed.
I dont believe a mechanical pump will supply enough fuel for your engine @ WOT. I ran an old Holley electric pump on my 512 other than the noise I never had any fuel issues. Never even ran a regulator and/or return line.I have checked the seporator and it's free and clear and, hooked up correctly.
The gauge is non fluid filled gauge in the rail right before the carb. The line to the pump is 3/8 and from the pump forward is all braided -6 an lines.I dont believe a mechanical pump will supply enough fuel for your engine @ WOT. I ran an old Holley electric pump on my 512 other than the noise I never had any fuel issues. Never even ran a regulator and/or return line.
What type of fuel pressure gauge do you have and where is it located?
What size fuel lines?
I have had them all off and inspected them, they all look good and they are also new."steel braided lines" rubber hose? checked for collapsing hoses or folded over inner layer hose at the insert
Its fine under WOT, its about an 1/8 down the road after you get out of the throttle when it has a problem.I dont believe a mechanical pump will supply enough fuel for your engine @ WOT. I ran an old Holley electric pump on my 512 other than the noise I never had any fuel issues. Never even ran a regulator and/or return line.
What type of fuel pressure gauge do you have and where is it located?
What size fuel lines?
Unfortunately you cant trust the accuracy of that gauge. They all go to zero under the hood from the heat. If you remote the gauge out from under the hood you will get a different story.The gauge is non fluid filled gauge in the rail right before the carb. The line to the pump is 3/8 and from the pump forward is all braided -6 an lines.
Sounds like you are draining the lines and it just takes 1/8 to empty the carb dry.Its fine under WOT, its about an 1/8 down the road after you get out of the throttle when it has a problem.
It will run WOT for as long as I want it to after I get out of the throttle it will run just fine for about an 1/8 of a mile before it looses pressure and dies. It also seems heat related as if the motor is cool it doesn't seem to do it.Sounds like you are draining the lines and it just takes 1/8 to empty the carb dry.
I ran 3/8 aluminum hard fuel lines from the tank thru the fuel pump all the way up the firewall and into the back of a dual hard line feed to a 950 cfm Holley. Ran a 1/2 thick thermal spacer under the carb - no issues.It will run WOT for as long as I want it to after I get out of the throttle it will run just fine for about an 1/8 of a mile before it looses pressure and dies. It also seems heat related as if the motor is cool it doesn't seem to do it.
You may be right. My new regulator will be here Wednesday so I will try it before i go with electric pump. I also have a 1/2 im phenolic spacer under the carb.I ran 3/8 aluminum hard fuel lines from the tank thru the fuel pump all the way up the firewall and into the back of a dual hard line feed to a 950 cfm Holley. Ran a 1/2 thick thermal spacer under the carb - no issues.
I still think you cant do this with a mechanical pump.
Prove me wrong, I hope you can.
It is possible, With the right pump. On the engine masters show Freiburger just made over 1000 hp on a BBC with a tunnel ram and two 4s naturally aspirated, all fed by a mechanical pump.I dont believe a mechanical pump will supply enough fuel for your engine @ WOT. I ran an old Holley electric pump on my 512 other than the noise I never had any fuel issues. Never even ran a regulator and/or return line.
What type of fuel pressure gauge do you have and where is it located?
What size fuel lines?