3/8 fuel lines and fuel pump - ClassicOldsmobile.com


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Old November 13th, 2017, 08:26 PM   #1  
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3/8 fuel lines and fuel pump

I have a 1966 cutlass, 455 with a quadrajet and realized this weekend that the fuel bowl was running dry while drag racing. Works great on the street but not so great when the 2-3 shift happens it just falls flat. It has the original 5/16 line, with new sending unit and fuel pump. Iím planning on switching over to 3/8 line but which fuel pump works with the 3/8 line. And which pump to carb hard line do I use?
Thanks
Dan
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Old November 14th, 2017, 12:02 AM   #2  
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I do know 65 Cutlass with a 330 is 5/16" and 65 442 400 motor is 3/8" that's one way to tell if real 442 or not but lines can be changed but body must lift up for replacement of 3/8" fuel lines.
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Old November 14th, 2017, 12:08 AM   #3  
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My street and strip 64 F-85 post had a 425 Olds with the stick W-30 cam and 400 trans with 350 convertor and a W-37 3.91 and 66 Tri-Power, posi ran 12.50 at 110 MPH all day never had a problem running out of gas with a 5/16" line. I think the tri power used more gas and never pinged.
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Old November 14th, 2017, 05:00 AM   #4  
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you may want to enlarge the tiny holes in the carb that fill the secondary wells,this worked for me when i transferred a 66 442 drivetrain into a 65 cutlass that had the same issue.
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Old November 14th, 2017, 06:14 AM   #5  
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Delete the mechanical pump and use a Holley red pump.
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Old November 14th, 2017, 10:38 AM   #6  
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Delete the mechanical pump and use a Holley red pump.
With 3/8 line?
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Old November 14th, 2017, 12:10 PM   #7  
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what qjet number are you using? There is a larger needle and seat available, drag racing may require a slightly higher fuel level setting. You may require a different pickup in the tank if fuel is rushing to the back of the tank during launch and leaving the pickup exposed. Larger lines and electric pumps are preferred. Contact Cliff Ruggles if possible. Good luck.
https://cliffshighperformance.com/
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Old November 14th, 2017, 03:42 PM   #8  
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Check out Cliffs feed back on running a return line in the form section.

Last edited by Bernhard; November 14th, 2017 at 03:44 PM.
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Old November 17th, 2017, 02:44 PM   #9  
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Thanks for replyís guys. The quad is a 7042040. I think itís a Buick carb used on their 455s. I emeailed Lars Grimsrud, I explained the situation and he said mostly likely fuel starvation. Iíve ordered a 3/8 sending unit and my fuel pump inlet is 3/8 so Iíll just have to figure out fuel line. I donít want to lift the body and I donít care about originality so Iíll just snake a braided line over the rear crossmember. Thatís my biggest concern with this retro fit. But Iíve got all winter to do this and some head work
It runs 8.55 in the 1/8 but id like it a little faster. Weíll see
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Old November 18th, 2017, 06:40 AM   #10  
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Sock on pick up could have collapsed or maybe another obstruction. Disconnect the fuel line at the pump and blow air in to clear it. The sock on my 66 collapsed flat.

Last edited by TripDeuces; November 18th, 2017 at 12:27 PM.
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Old November 18th, 2017, 08:49 AM   #11  
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With 3/8 line?
yes, that is what I run.
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Old November 18th, 2017, 09:34 AM   #12  
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yes, that is what I run.
Hi

What kind of pump are you running and are you using a return line?
How fast is the car ET MPH and when do you think a 1/2 inch line would be the way to go?
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Old November 18th, 2017, 12:41 PM   #13  
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Iím not sure on what brand the pump is. Itís from rock auto There isnít a return line on it. The sending unit is less than a year old but itís a 5/16 line size unit.
What Iím going to try to do is cut the barbed fittings off of the pump and sending unit and use earls hardline adapters to -6an fittings and run braided 3/8 line from tank to pump
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Old November 18th, 2017, 12:44 PM   #14  
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The car ran an 8.55 at 84 mph in 45 degree weather last week. Thatís the best itís ever gone but I couldnít duplicate that and it was running 8.6 to 8.7 with the fuel problems If I kept it floored is when the problems happened so if I only was in it 3/4 throttle it would run ok but thatís hard to modulate during a race
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Old November 18th, 2017, 12:48 PM   #15  
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One last thing Sorry about all the posts I keep thinking of stuff to add
If I go up to 1/2 inch line that raises more problems. Is there a fuel pump with 1/2Ē fittings? How about a 1/2Ē sending unit? And Iíd need a 1/2Ē line from pump to carb. Just brain storming here
Thank you everyone for your input
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Old November 18th, 2017, 01:34 PM   #16  
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Are you going to be using the 5/16 line as a return?
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Old November 18th, 2017, 01:36 PM   #17  
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before you get too crazy, install a fuel pressure gauge where you can see it while driving. you want to verify fuel pressure is falling off before you spend a ton of money and time on upgrades. good luck
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Old November 18th, 2017, 01:46 PM   #18  
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Good point shiftbyear. Iíll do that once itís back together. Iím gonna do some head work this winter so itís down for the for seeable future

Bernhard Iím not going to run a return line. I couldnít find cliffs write up on return lines. I even looked over at his forum and the only return line mention was about running an electric pump.
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Old November 18th, 2017, 05:54 PM   #19  
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Oldsmobile ran a return line with a mechanical pump on 442's, W 31's etc.
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Old November 19th, 2017, 05:44 AM   #20  
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Quote:
Originally Posted by Daniel828 View Post
Iím not sure on what brand the pump is. Itís from rock auto There isnít a return line on it. The sending unit is less than a year old but itís a 5/16 line size unit.
What Iím going to try to do is cut the barbed fittings off of the pump and sending unit and use earls hardline adapters to -6an fittings and run braided 3/8 line from tank to pump
sounds like a lot of work and expense for something that could be solved by enlarging the secondary fill holes,i'm running stock 5/16 line on my 65 cutlass with no problems after enlarging them.stock fuel pump,455,q jet,4 spd,4:33s running [email protected]
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Old November 19th, 2017, 06:09 AM   #21  
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Hi

What kind of pump are you running and are you using a return line?
How fast is the car ET MPH and when do you think a 1/2 inch line would be the way to go?
I run the Holley red pump (no regulator), screen filter at the pump which is near the tank, no return line. I have an Autometer electric fuel pressure gauge with the sender mounted at the carb inlet. Car has run 11.51, 118.97.
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Old November 19th, 2017, 07:57 AM   #22  
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Good point bernhard, I didnít realize that

Jcdynamic88, I have Ruggles quadrajet book. Does it mention anything about the secondary enlargement? Iím curious about this and would like to learn more about that mod.
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Old November 19th, 2017, 09:34 AM   #23  
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I run the Holley red pump (no regulator), screen filter at the pump which is near the tank, no return line. I have an Autometer electric fuel pressure gauge with the sender mounted at the carb inlet. Car has run 11.51, 118.97.
Thanks for the reply.

11.51 118.97 WOW

This is with your JR stock 400 E right ?

Is the key to your fuel system the lack of restriction as in no regulator and screen filter?
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Old November 19th, 2017, 10:55 AM   #24  
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Good point bernhard, I didnít realize that

Jcdynamic88, I have Ruggles quadrajet book. Does it mention anything about the secondary enlargement? Iím curious about this and would like to learn more about that mod.
i've been modifying and racing q-jets for over 40 years and i don't remember where i picked up that tip but it works.there are two tiny holes that fill the secondary wells and it's easy to enlarge them .i believe to 1/16 "
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Old November 21st, 2017, 07:49 AM   #25  
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No special key to my fuel system. The red pump is Holley's "basic" pump with internal regulation to 7 pounds, no external regulator--the blue pump runs 15 lb. and regulates down near the carb. The screen filter is Jegs 15040 filter, 40 micron screen. I run a Caddy Seville fuel pump hole cover from its 350 Olds engine.
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Old November 21st, 2017, 07:41 PM   #26  
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No special key to my fuel system. The red pump is Holley's "basic" pump with internal regulation to 7 pounds, no external regulator--the blue pump runs 15 lb. and regulates down near the carb. The screen filter is Jegs 15040 filter, 40 micron screen. I run a Caddy Seville fuel pump hole cover from its 350 Olds engine.
Thanks for the reply.
I'm a fan of NHRA Stock and the fuel systems I have seen on cars that are not as quick as your car are extremely elaborate.
There is a mirror thread to this on ROP and one of the members their has also noted the hi tech fuel systems found on Stock class cars today.
I was just trying to under stand how you were able to make a dead head system with 3/8 line work so well.
Thanks again for the feed back.
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Old November 22nd, 2017, 03:42 AM   #27  
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i've been modifying and racing q-jets for over 40 years and i don't remember where i picked up that tip but it works.there are two tiny holes that fill the secondary wells and it's easy to enlarge them .i believe to 1/16 "




Photos ? Video ? or should he send it to you
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Old November 22nd, 2017, 04:12 AM   #28  
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[QUOTE=firefrost gold;1057435]Photos ? Video ? or should he send it to you [/QU after removing the top of the q jet it's self explanatory,after all it's not rocket surgery.
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Old November 22nd, 2017, 07:06 AM   #29  
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One caveat for you--I run Tri-Carbs which have decent sized fuel bowls. The Quadrajet has a tiny bowl so is very sensitive to fuel supply. With the Holley mechanical pump, I used to run out of fuel at around the 1/8 mile mark, when the car ran 12s.
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Old November 22nd, 2017, 08:15 PM   #30  
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Back in the day it was standard for out fast Olds to run a holley red back at the tank and then up to the mechanical fuel pump, and no fuel problems. If I remember right we could switch off the electric in normal driving and just run off the mechanical.
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Old November 23rd, 2017, 10:14 AM   #31  
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One caveat for you--I run Tri-Carbs which have decent sized fuel bowls. The Quadrajet has a tiny bowl so is very sensitive to fuel supply. With the Holley mechanical pump, I used to run out of fuel at around the 1/8 mile mark, when the car ran 12s.

Thanks for the reply and lesson.
So your system might not support a 11.50 Quardrajet car but works fine with the Tri power set up.
So the elaborate stock class fuel system, just removes any possible concern with fuel delivery
given the Quadrajet bowl size.
Now that I think about it,the cars that I seen with these expensive fuel systems were all running Q-jets.
Next points meet I'm going to pay closer attention to what non Q-jet cars are running for fuel delivery systems.

Last edited by Bernhard; November 23rd, 2017 at 10:21 AM.
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Old November 23rd, 2017, 04:04 PM   #32  
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[QUOTE=Bernhard;1057724]Thanks for the reply and lesson.
So your system might not support a 11.50 Quardrajet car but works fine with the Tri power set up.
So the elaborate stock class fuel system, just removes any possible concern with fuel delivery
given the Quadrajet bowl size.
Now that I think about it,the cars that I seen with these expensive fuel systems were all running Q-jets.
Next points meet I'm going to pay closer attention to what non Q-jet cars are running for fuel delivery systems.[/QUOTE

Dwight Kohout said on his 455 I believe he had fuel problems around mid to low 12s 111mph plus with his mechanical fuel pump supply to his Quadrajet, and added an electric pump booster to get down to about 12 flat without problems.

A 3/8Ēid fuel line can easily support 600 HP given sufficient ďpump headĒ! Given a big enough pump a 3/8Ē steel line could support 1000 HP.

http://ipgparts.com/blog/fuel-line-s...ize-do-i-need/
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