Factory pump to carb questions.
#1
Member
Thread Starter
Join Date: Aug 2009
Location: AZ
Posts: 332
Likes: 0
Received 0 Likes
on
0 Posts
Car: 1978 Chevrolet impala
Engine: 350ci 300hp/356tq pace crate
Transmission: 700r4
Axle/Gears: 3.42 Yukon posi
Factory pump to carb questions.
I carbed my '88 firebird about a year ago and went through the trouble of doing it right with a diaphragm regulator and all that other jazz. Now because I know the factory pumps aren't exactly known for their longevity, I want to examine my options for replacement.
I've read in a thread here on TGO that somebody actually rigged up a mechanical pump and ran it through his factory return line. How feasible is this? Will this still pull fuel until the tank is empty? Will I need a vented cap?
On a sidenote, if this IS in fact a possibility (I'd like to avoid dropping the tank. That's a buttload of work I could do without) will a L31 out of a '96 suburban come with the proper cam lobe to support a mechanical pump? and if not is it feasible to use an electric fuel pump out of the return line?
Thanks for your input.
I've read in a thread here on TGO that somebody actually rigged up a mechanical pump and ran it through his factory return line. How feasible is this? Will this still pull fuel until the tank is empty? Will I need a vented cap?
On a sidenote, if this IS in fact a possibility (I'd like to avoid dropping the tank. That's a buttload of work I could do without) will a L31 out of a '96 suburban come with the proper cam lobe to support a mechanical pump? and if not is it feasible to use an electric fuel pump out of the return line?
Thanks for your input.
#2
Supreme Member
Re: Factory pump to carb questions.
Fuel pump lobes started disappearing from factory installed cams in the early 90s. So, no, I doubt the cam in that Vortec motor would have a fuel pump lobe.
Also, you can't just bolt on a mechanical pump and draw through a non-functional factory in-tank (too much restriction). Never paid that much attention to the return line but I seriously dobt it goes all the way to the bottom of the tank like the pickup side does.
Also, you can't just bolt on a mechanical pump and draw through a non-functional factory in-tank (too much restriction). Never paid that much attention to the return line but I seriously dobt it goes all the way to the bottom of the tank like the pickup side does.
#3
TGO Supporter
Join Date: Oct 2002
Location: Saskatoon, SK, Canada
Posts: 9,067
Likes: 0
Received 1 Like
on
1 Post
Car: '83 Z28, '07 Charger SRT8
Engine: 454ci, 6.1 Hemi
Transmission: TH350, A5
Axle/Gears: 2.73 posi, 3.06 posi
Re: Factory pump to carb questions.
A factory L31 block likely isn't machined for the mechanical pump. Some may have been, but I've never seen one that was.
#4
Supreme Member
Join Date: Jul 2006
Location: 212 is up in this Bit@#
Posts: 2,761
Received 739 Likes
on
565 Posts
Car: Resto-Mod 1987 IROC-Z Clone
Engine: Alky fed L92 Vortec Twin-Turbo 6.8L
Transmission: My own built/ design 4L80M
Axle/Gears: Custom 12 bolt (4.10:1)
Re: Factory pump to carb questions.
From the L31 blocks i have used in my cars, the 96-97 blocks had provisions for a mechanical fuel pump push rod... the 98+ blocks do not have a hole drilled for the push rod. All have a mounting boss.
Thread
Thread Starter
Forum
Replies
Last Post
84z96L31vortec
Tech / General Engine
7
08-20-2017 12:16 AM
theshackle
Tech / General Engine
4
03-05-2017 06:37 PM
beachrodder
Tech / General Engine
7
08-25-2015 08:05 AM
84z96L31vortec
North East Region
1
08-10-2015 08:27 PM