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


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Old November 13th, 2017, 09:26 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, 01:02 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, 01:08 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, 06:00 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, 07:14 AM   #5
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Delete the mechanical pump and use a Holley red pump.
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Old November 14th, 2017, 11:38 AM   #6
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Quote:
Originally Posted by Run to Rund View Post
Delete the mechanical pump and use a Holley red pump.
With 3/8 line?
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Old November 14th, 2017, 01:10 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, 04:42 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 04:44 PM.
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Old Yesterday, 03:44 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 Today, 07:40 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; Today at 01:27 PM.
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Old Today, 09:49 AM   #11
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With 3/8 line?
yes, that is what I run.
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Old Today, 10:34 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 Today, 01:41 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 Today, 01:44 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 Today, 01:48 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 Today, 02:34 PM   #16
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Are you going to be using the 5/16 line as a return?
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Old Today, 02:36 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 Today, 02:46 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 Today, 06:54 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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