Fuel pump return line necessary?
Thread Starter
Drifting
Joined: Nov 2000
Posts: 1,361
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From: Honolulu Hawaii
Fuel pump return line necessary?
Is the fuel return line necessary if the replacement fuel pump does not come with it? Many here have been very resourceful in helping me choose a replacement performance fuel pump. Some of the ones recommended only come with an inlet/outlet setup, no return line. Just wondering if it is really needed. Thanks to all.
Pro
Joined: Jun 2001
Posts: 683
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From: Calgary
Re: Fuel pump return line necessary? (nunus79)
When I purchased the Holley mech. fuel pump for my 74, it had no provision for the fuel return (vent?) line. All it had was suction and discharge. I just plugged the return/vent line in an inconspicious spot and have had no problems.
Race Director
Joined: Oct 2000
Posts: 15,009
Likes: 79
From: central FL, near the beach.
Re: Fuel pump return line necessary? (nunus79)
i put a T with a 1/16 restriction returning fuel to the tank, as i live in FL and don't want vapor lock, or hot fuel going to the carb. no problems 3 years so far.
but, if i lived in a cold climate, i would not bother
but, if i lived in a cold climate, i would not bother
Instructor
Joined: Jul 2001
Posts: 183
Likes: 0
From: Brighton MI
Re: Fuel pump return line necessary? (nunus79)
I replaced my stock pump with a hi-po model that did not have a provision for a return line. I did start to have vapor locking problems. These were more or less resolved by getting as much heat away from the fuel lines as possible. When I re-engine the car in the near future, I'll probably go back to a return line set up.
Burning Brakes
Joined: Sep 1999
Posts: 931
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From: MI
Re: Fuel pump return line necessary? (nunus79)
I concurred with 72stingray. The return line is a big relief of pressure build up from vapor lock, when the engine is hot under the hood, especially, the HP motor. All my Vettes have return lines. Been there, and learned my lesson.
[Modified by Ki m Le, 7:45 AM 9/14/2001]
[Modified by Ki m Le, 7:45 AM 9/14/2001]
Melting Slicks
Joined: Jun 2001
Posts: 2,429
Likes: 14
From: CA
Re: Fuel pump return line necessary? (Ki m Le)
I remember reading that LT-1's, LS-6's & some high power 427's only had the one fuel line & no return.
We will have to wait for Joe Lucia to confirm this... :cheers:
We will have to wait for Joe Lucia to confirm this... :cheers:
Thread Starter
Drifting
Joined: Nov 2000
Posts: 1,361
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From: Honolulu Hawaii
Re: Fuel pump return line necessary? (71coupe)
Thank you all for sharing your knowledge! Sounds like it is probably going to be needed in Hawaii. I've read Joe Lucia's & drives61's rec replacement p/n from another thread that should have the return line. Going to start there and see if the specs match up to my needs. Again thank you all for your replies. You guys are a great bunch!
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Team Owner
Joined: Jun 2000
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From: Southbound
Cruise-In II Veteran
Re: Fuel pump return line necessary? (nunus79)
The return line was an emissions thingie. It's on my '68 and is not on my '80. There is also a small metal return line from the stock in-line fuel filter connecting to the return line at the chassis.
Drifting
Joined: Nov 2000
Posts: 1,390
Likes: 39
From: North Brunswick NJ
Re: Fuel pump return line necessary? (nunus79)
The return line is not necessary and the Holley equipped Corvettes did not have a return line. It is nice when you are operating in a hot climate to have a return line so that you dont have vapor lock or percolation.
Ed
Ed
Burning Brakes
Joined: Jan 2001
Posts: 1,004
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From: Gainesville, Florida
Re: Fuel pump return line necessary? (ED DINAPOLI)
I have no return line, live in a relatively hot climate and suffer no vapor lock or fuel percolation. Maybe the carb spacer and Air Gap intake helps isolate the carb....and the coated headers really reduce compartment heat as well.
Mark
Mark
Thread Starter
Drifting
Joined: Nov 2000
Posts: 1,361
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From: Honolulu Hawaii
Re: Fuel pump return line necessary? (Red73)
Thanks guys for the additional input. Got me thinking. Where does vapor lock occur? at the pump? at the carb? in the line?
Rod
How did you size the return flow line? Wouldn't to big a return line lessen the pressure & flow at the carb?
Excuse my ignorance on this stuff. The more I've looked into this, the more I questions I have. This type of problem has always been a problem for some other guy, so I never paid to much attention to learning about fuel systems. Thanks guys, for walking me thru this.
Rod
How did you size the return flow line? Wouldn't to big a return line lessen the pressure & flow at the carb?
Excuse my ignorance on this stuff. The more I've looked into this, the more I questions I have. This type of problem has always been a problem for some other guy, so I never paid to much attention to learning about fuel systems. Thanks guys, for walking me thru this.
Drifting
Joined: Sep 1999
Posts: 1,411
Likes: 1
From: Wylie TX
Re: Fuel pump return line necessary? (nunus79)
I beleive vapor lock is in the line.
Red73, is that a Holley 803 regulator? If so, how do you restrict the flow back to the return line (I think this is what nunus79 is asking to)? I just installed one of those regulators and for now, I just have one of the outlets plugged. I was going to fight the return line battle later.
I had (wrongly) assumed that the third port was for a return line to get rid of the extra gas, but it is just another outlet port for a dual feed carb, I guess.
Red73, is that a Holley 803 regulator? If so, how do you restrict the flow back to the return line (I think this is what nunus79 is asking to)? I just installed one of those regulators and for now, I just have one of the outlets plugged. I was going to fight the return line battle later.
I had (wrongly) assumed that the third port was for a return line to get rid of the extra gas, but it is just another outlet port for a dual feed carb, I guess.
Thread Starter
Drifting
Joined: Nov 2000
Posts: 1,361
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From: Honolulu Hawaii
Re: Fuel pump return line necessary? (Chris A)
Chris
Thanks for the answer. Yes, I'm wondering about the return line restriction/sizing. I guess the original return line sizing provides the needed restriction.
So do you think if the fuel line from the pump to the carb is bent in a way to avoid vapor pockets from collecting then no vapor lock problems will exist?
PS I think I'm going to try that Weiand 7525 too. When will that 383 be up & running?
Thanks for the answer. Yes, I'm wondering about the return line restriction/sizing. I guess the original return line sizing provides the needed restriction.
So do you think if the fuel line from the pump to the carb is bent in a way to avoid vapor pockets from collecting then no vapor lock problems will exist?
PS I think I'm going to try that Weiand 7525 too. When will that 383 be up & running?
Safety Car
Joined: Aug 1999
Posts: 4,862
Likes: 118
From: Texas
Re: Fuel pump return line necessary? (71coupe)
I remember reading that LT-1's, LS-6's & some high power 427's only had the one fuel line & no return.
We will have to wait for Joe Lucia to confirm this... :cheers:
We will have to wait for Joe Lucia to confirm this... :cheers:
Le Mans Master
Joined: Apr 1999
Posts: 6,134
Likes: 46
From: Raleigh North Carolina
Re: Fuel pump return line necessary? (Cam Potter)
My LS5 has the return line. Also, Holley made a fuel pump with the return line. But I believe it may have been discontinued. I have one in a box somewhere. Vapor Lock occurs due to over-heated/vaporized fuel. Not because of any specific line curvature. You can have vapor lock in a perfectly straight piece of fuel line given high enough temperatures. Vapor lock is a function of the ambient temperature in an engine compartment, and how far from stock you have modified your engine compartment. So, once a Vette has been changed from stock, a discussion on vapor lock of one Vette vs another is usually moot because we are in "apples & oranges" mode. This is especially true of BB vs SB engines. The BB's produce a higher volume of heat.
Drifting
Joined: Sep 1999
Posts: 1,411
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From: Wylie TX
Re: Fuel pump return line necessary? (nunus79)
nunus, if you get the Weinad 7525 manifold, you might want to also get allen head bolts. The manifold is made to accept every manifold add-on created (EGR, hot air choke, hot air crossover, etc). Becaus of this, the 2 middle bolts on the passenger would be impossble to get a normal wrench on.
I've actually fired up the 383 last weekend. It ran fine once I found the correct timing (it was about 30 degrees off my first try), but I had a pretty good oil leak from the rear of the intake manifold. There is something really weird with my block/heads/manifold setup and it is real work to get the manifold on. Well, it turns out that the rear of the manifold did not compress the gasket at all (it barely touched it), so oil just spewed out the back. I just finished replacing it, but it's probably going to leak again. I ended up using some MR Gasket manifold gaskets and I don't like the way the manifold gaskets mate up from the block to the heads. I went ahead and put everything back together and I'll try again tomorrow afternoon. If it leaks again, I'll get some Fel-Pro (cannot find the 1206 or 1256 locally) gaskets again and goop the heck out of the rear seal.
I've actually fired up the 383 last weekend. It ran fine once I found the correct timing (it was about 30 degrees off my first try), but I had a pretty good oil leak from the rear of the intake manifold. There is something really weird with my block/heads/manifold setup and it is real work to get the manifold on. Well, it turns out that the rear of the manifold did not compress the gasket at all (it barely touched it), so oil just spewed out the back. I just finished replacing it, but it's probably going to leak again. I ended up using some MR Gasket manifold gaskets and I don't like the way the manifold gaskets mate up from the block to the heads. I went ahead and put everything back together and I'll try again tomorrow afternoon. If it leaks again, I'll get some Fel-Pro (cannot find the 1206 or 1256 locally) gaskets again and goop the heck out of the rear seal.
Team Owner
Joined: Apr 1999
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From: Reno Nevada
2024 C3 of the Year Finalist- Modified
Re: Fuel pump return line necessary? (Chris A)
Chris Some manifolds like the weiands require some manifold grinding to get more than a 1/4 turn and move the wrench action. I always used 7/16th small header type bolts and allens on everything else. Never use a cork or rubber gasket. Permatex blue goop is all you need. Use the factory pattern to tighten all bolts. I use red spray sealer on the head side only and blocking plates for the cross over.
I don't know what kind of heads you have but 1206 is pretty big. Only bigger single planes even need them. 1205 is a more typical. Order them through http://www.summitracing.com
I don't know what kind of heads you have but 1206 is pretty big. Only bigger single planes even need them. 1205 is a more typical. Order them through http://www.summitracing.com