Fuel Pump Differences - The 1947 - Present Chevrolet & GMC Truck Message Board Network

stllookn · 04-26-2004, 12:34 AM

I noticed the '72 350/TH400 Cheyenne has a fuel pump with three outlets, while the '72 GMC/TH400 has a two outlet pump. The auto parts store says only the stick had a two outlet pump but both of these vehicles are stock. Can I switch to the two outlet pump, since it is half price?

69ride · 04-26-2004, 12:47 AM

my 454 had a three outlets and i switched to a two outlet and didn't encounter any problems... well I did send number one piston into orbit but I don't think that had anything to do with that

The three outlet is a inlet, outlet to carb and a return to tank I believe but I could be wrong

stllookn · 04-26-2004, 01:03 AM

That is what I thought too...but why would the tranny make a difference as to whether it needs the return to tank?

**kwmech** · 04-26-2004, 01:30 AM

Thinking back that far as to what the differences were/are I think AC had something to do with it. Extra heat? Vapor loc?

**'68OrangeSunshine** · 04-26-2004, 05:01 AM

Outlet #3 was for the vapor return line. Required on Calif vehicles.
I deleted a 3-holer on mine and went for a non-emission unit. [The ones NAPA sells are made by Carter in the USA.] Better performance and no more mystery fuel leaks.

04-26-2004, 12:34 AM	#1
stllookn Saving 1 truck at a time! Join Date: Aug 2001 Location: Kent, WA Posts: 6,465	Fuel Pump Differences I noticed the '72 350/TH400 Cheyenne has a fuel pump with three outlets, while the '72 GMC/TH400 has a two outlet pump. The auto parts store says only the stick had a two outlet pump but both of these vehicles are stock. Can I switch to the two outlet pump, since it is half price? __________________ '68 C20 Longhorn 50th Anniversary 400/TH400 '68 C20 Longhorn 50th Anniversary 468/TH400w/buckets '72 C20 Halfhorn (Longhorn w/o cab and front clip) '69 Flxible Cruiser (look up ugly in the dictionary)

04-26-2004, 12:47 AM	#2
69ride All Go, No Show Join Date: Jul 2003 Location: Creighton SK Posts: 286	my 454 had a three outlets and i switched to a two outlet and didn't encounter any problems... well I did send number one piston into orbit but I don't think that had anything to do with that The three outlet is a inlet, outlet to carb and a return to tank I believe but I could be wrong __________________ 69 LWB Rebuilt 283, aluminum intake, edelbrock carb, Mild Melling Cam, HEI.

04-26-2004, 05:01 AM	#5
'68OrangeSunshine Senior Member Join Date: Feb 2002 Location: Tucson, AZ USA Posts: 7,537	EMIS VAPOR RTN LINE Outlet #3 was for the vapor return line. Required on Calif vehicles. I deleted a 3-holer on mine and went for a non-emission unit. [The ones NAPA sells are made by Carter in the USA.] Better performance and no more mystery fuel leaks.

04-26-2004, 01:03 AM	#3
stllookn Saving 1 truck at a time! Join Date: Aug 2001 Location: Kent, WA Posts: 6,465	That is what I thought too...but why would the tranny make a difference as to whether it needs the return to tank? __________________ '68 C20 Longhorn 50th Anniversary 400/TH400 '68 C20 Longhorn 50th Anniversary 468/TH400w/buckets '72 C20 Halfhorn (Longhorn w/o cab and front clip) '69 Flxible Cruiser (look up ugly in the dictionary)

04-26-2004, 01:30 AM	#4
kwmech Senior Member Join Date: Mar 2003 Location: Colfax-California Posts: 8,659	Thinking back that far as to what the differences were/are I think AC had something to do with it. Extra heat? Vapor loc?



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