Easy Fuel pump question...Help Guys! - The 1947 - Present Chevrolet & GMC Truck Message Board Network

nejeff · 07-31-2003, 08:23 PM

I am replacing a stock 72' 350 4-barrel and it has two lines going into the bottom of the fuel pump. The motor I am replacing it with is a 72' also , a 307 2-barrel and it has one line feeding it with fuel.

What the hell do I do with the second line and what is it their for?

I need help guys!!

nejeff · 07-31-2003, 08:45 PM

ttt---help!

nejeff · 07-31-2003, 09:02 PM

Guys!! I really need to know what's up!! Please let me know
'
Thanks

my new 72 · 07-31-2003, 09:12 PM

One is a return line. Just plug the return line and run it.

jef5150 · 07-31-2003, 09:20 PM

the fuel pump should have 2 places to connect lines.......1 line goes to the gas tank [inlet] and the 2nd line [outlet] goes to the carb,,,,,,,,,

nejeff · 07-31-2003, 09:23 PM

Mine has three total...two on bottom and one going to the carb. WHich one do I plug if one of them is the return line?

Thanks guys

Jeff

lukecp · 07-31-2003, 09:41 PM

Just run the fuel pump for the 350 on the 307...it should bolt right up. It has been awhile since i have replaced a fuel pump, but i am pretty sure all of the lines have different sized fittings so you can't mess them up. If you want to use the 307 pump, the smaller line going back towards the tank is the return line, plug it.

lukecp · 07-31-2003, 09:46 PM

oops...i re-read your post, you are hooking it up to a 2bbl carb....i believe that is what determines the difference in the fuel pump, the 4bbl pump has a return line, and the 2-bbl dosen't. In that case, just plug the smaller return line....OR

Put your 4bbl intanke and carb on the 307 and run the 350 fuel pump. Gotta have a 4bbl

**Stocker** · 07-31-2003, 10:02 PM

Quote:

Originally posted by yellow72custom
the 4bbl pump has a return line, and the 2-bbl dosen't.

Just checked - my OEM Q-jet 350 has 2 lines...

**StingRay** · 07-31-2003, 10:36 PM

If it's a 72 307 don't try that 4 bbl without the 350 heads as well. the 72 307 has tiny little ports and won't be the effort of a 4 bbl swap without better heads.

lukecp · 07-31-2003, 10:37 PM

When mine was a OEM Q-jet 350, TH350 truck, it had 3 lines, one going to the carb, and two going from the tank to the pump

nejeff · 07-31-2003, 10:52 PM

I think I'll just swap the fuel pumps and save myself from having to think too much!

Really, thanks for all the info

Jeff

my new 72 · 07-31-2003, 10:59 PM

Oh yeah, I forgot to mention that the bottom of the pump is market inlet outlet, and return.

smokekiki · 08-01-2003, 08:55 AM

The return line was there to circulate fuel around the inside of the pump.This was to keep the pump cooler to prevent vapor lock.

Gordo · 08-01-2003, 09:20 PM

You can swap pumps but you may find the outlet from the pump to the 2 bl carb on the 307 takes a 5/16" fuel line and the 350 with the 4 bl takes a 3/8" line. So you will have to fab the two together.

Z-72 · 08-02-2003, 09:18 AM

I just had that problem myself, had bad problems with vapor lock until I put the two line pump back on. No problems now.

nejeff · 08-02-2003, 11:17 AM

I am going to try the stock 307 pump first and then switch if I have trouble. Thanks for all the information!

Jeff

07-31-2003, 08:23 PM	#1
nejeff Registered User Join Date: Jun 2003 Location: Nebraska Posts: 63	Easy Fuel pump question...Help Guys! I am replacing a stock 72' 350 4-barrel and it has two lines going into the bottom of the fuel pump. The motor I am replacing it with is a 72' also , a 307 2-barrel and it has one line feeding it with fuel. What the hell do I do with the second line and what is it their for? I need help guys!! __________________ 72' Chevy Super Cheyenne LWB 72' Chevy C-10 (307 Parts Truck)

07-31-2003, 08:45 PM	#2
nejeff Registered User Join Date: Jun 2003 Location: Nebraska Posts: 63	ttt---help! ttt---help! __________________ 72' Chevy Super Cheyenne LWB 72' Chevy C-10 (307 Parts Truck)

07-31-2003, 09:02 PM	#3
nejeff Registered User Join Date: Jun 2003 Location: Nebraska Posts: 63	Guys!! I really need to know what's up!! Please let me know ' Thanks __________________ 72' Chevy Super Cheyenne LWB 72' Chevy C-10 (307 Parts Truck)

07-31-2003, 09:12 PM	#4
my new 72 faster, faster, faster Join Date: Dec 2001 Location: Houston ,Texas ,USA Posts: 1,354	One is a return line. Just plug the return line and run it. __________________ I'm going to Law School, wanna debate? It's good practice.

07-31-2003, 09:23 PM	#6
nejeff Registered User Join Date: Jun 2003 Location: Nebraska Posts: 63	Mine has three total...two on bottom and one going to the carb. WHich one do I plug if one of them is the return line? Thanks guys Jeff __________________ 72' Chevy Super Cheyenne LWB 72' Chevy C-10 (307 Parts Truck)

07-31-2003, 09:20 PM	#5
jef5150 Inline 69 Join Date: Apr 2003 Location: valleysprings,california Posts: 1,018	the fuel pump should have 2 places to connect lines.......1 line goes to the gas tank [inlet] and the 2nd line [outlet] goes to the carb,,,,,,,,,

07-31-2003, 09:41 PM	#7
lukecp Formerly yellow72custom Join Date: May 2001 Location: Austin, TX Posts: 7,531	Just run the fuel pump for the 350 on the 307...it should bolt right up. It has been awhile since i have replaced a fuel pump, but i am pretty sure all of the lines have different sized fittings so you can't mess them up. If you want to use the 307 pump, the smaller line going back towards the tank is the return line, plug it. __________________ '72 Chevy C10 Mild 350/TH350/3.07. Ochre/White. Old high school ride. '70 GMC C2500 '62 327 4bbl/SM465/4.56-geared Dana 60. White/White. Project or parts truck. '97 Saturn SL DD. 1.9/5-speed. 40+ highway mpg

07-31-2003, 09:46 PM	#8
lukecp Formerly yellow72custom Join Date: May 2001 Location: Austin, TX Posts: 7,531	oops...i re-read your post, you are hooking it up to a 2bbl carb....i believe that is what determines the difference in the fuel pump, the 4bbl pump has a return line, and the 2-bbl dosen't. In that case, just plug the smaller return line....OR Put your 4bbl intanke and carb on the 307 and run the 350 fuel pump. Gotta have a 4bbl __________________ '72 Chevy C10 Mild 350/TH350/3.07. Ochre/White. Old high school ride. '70 GMC C2500 '62 327 4bbl/SM465/4.56-geared Dana 60. White/White. Project or parts truck. '97 Saturn SL DD. 1.9/5-speed. 40+ highway mpg

07-31-2003, 10:36 PM	#10
StingRay Senior Member Join Date: Mar 2000 Location: Saskatoon,SK,Canada Posts: 2,476	If it's a 72 307 don't try that 4 bbl without the 350 heads as well. the 72 307 has tiny little ports and won't be the effort of a 4 bbl swap without better heads. __________________ Saskatoon, Saskatchewan Canada

07-31-2003, 10:37 PM	#11
lukecp Formerly yellow72custom Join Date: May 2001 Location: Austin, TX Posts: 7,531	When mine was a OEM Q-jet 350, TH350 truck, it had 3 lines, one going to the carb, and two going from the tank to the pump __________________ '72 Chevy C10 Mild 350/TH350/3.07. Ochre/White. Old high school ride. '70 GMC C2500 '62 327 4bbl/SM465/4.56-geared Dana 60. White/White. Project or parts truck. '97 Saturn SL DD. 1.9/5-speed. 40+ highway mpg

07-31-2003, 10:52 PM	#12
nejeff Registered User Join Date: Jun 2003 Location: Nebraska Posts: 63	Thanks alot guys! I think I'll just swap the fuel pumps and save myself from having to think too much! Really, thanks for all the info Jeff __________________ 72' Chevy Super Cheyenne LWB 72' Chevy C-10 (307 Parts Truck)

07-31-2003, 10:59 PM	#13
my new 72 faster, faster, faster Join Date: Dec 2001 Location: Houston ,Texas ,USA Posts: 1,354	Oh yeah, I forgot to mention that the bottom of the pump is market inlet outlet, and return. __________________ I'm going to Law School, wanna debate? It's good practice.

08-01-2003, 08:55 AM	#14
smokekiki Mike Join Date: Jan 2003 Location: west chester pa Posts: 2,473	The return line was there to circulate fuel around the inside of the pump.This was to keep the pump cooler to prevent vapor lock. __________________ 70'c/10, 71 suburban4x4 402bb, 72suburban 4/6 drop, 72k/5 4x4 blazer 4" lift 35 tires

08-01-2003, 09:20 PM	#15
Gordo Registered User Join Date: Jan 2001 Location: Killingworth, CT. USA Posts: 3,378	You can swap pumps but you may find the outlet from the pump to the 2 bl carb on the 307 takes a 5/16" fuel line and the 350 with the 4 bl takes a 3/8" line. So you will have to fab the two together. __________________ 1971 C10 swb stepside 350/700R4/3.73posi (retired as of 4/22/03) 1998 S10 short bed 2002 S10 Blazer 1942 Oldsmobile 1958 Massey Harris Pony 1951 Wife Killingworth, Connecticut May those who love us, love us, any of those who do not love us, may God turn their hearts. And if God is unable to turn their hearts, may he turn their ankles so we may know them by their limping. A man who works with his hands is a laborer; a man who works with his hands and his brain is a craftsman; but a man who works with his hands and his brain and his heart is an artist.

08-02-2003, 09:18 AM	#16
Z-72 Registered User Join Date: Dec 2002 Location: south-east kansas Posts: 68	I just had that problem myself, had bad problems with vapor lock until I put the two line pump back on. No problems now. __________________ 72-C-10-LWB-Big Block-TH400- PosiTrac Leaf Springs- A Dark Green Ford Eaten Machine. And those are not rust holes, there cooling vents..



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08-02-2003, 11:17 AM	#17
nejeff Registered User Join Date: Jun 2003 Location: Nebraska Posts: 63	Thanks guys! I am going to try the stock 307 pump first and then switch if I have trouble. Thanks for all the information! Jeff __________________ 72' Chevy Super Cheyenne LWB 72' Chevy C-10 (307 Parts Truck)

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