Double pumper Q's
Thread Starter
Member
Joined: Oct 2007
Posts: 123
Likes: 0
Car: 1986 Trans Am
Engine: 350 4BBL
Transmission: T5
Axle/Gears: 3.70
Double pumper Q's
Ran the numbers on my carb and found out it was a 600 cfm DP holly list number 4776-2 (1587) not sure what the rest of the numbers are but anyway I was just wondering whats the difference in a DP and a normal carb other than the obvious two fuel lines and bowls but is there performance to be had with it or what? Current setup is 80 350 block .30 over 64-67 327 camel hump heads and a wiend intake and the carb above. Also when the car comes out next month you will be hearing from me about tunning cause its not running right and you all will be happy to know that I intend to do all the carb rebuilding myself and tunning.....cause its the only way I will figure it out haha done plenty of work on my own stuff but never on a carb so it should be interesting.
Member
Joined: Jan 2008
Posts: 274
Likes: 0
From: Kitchener, ONT
Car: 2000 SS, M6
Engine: Modified LS1
Transmission: T-56
Axle/Gears: 3.42
Re: Double pumper Q's
For your street engine, you will likely not see any gains...unless you
drive wide open for long periods of time.
The obvious benefit of the dual fuel line is that you have equal inlet
pressure at each bowl instead of the rear feeding from the front line.
You may notice an improvement on the drag strip as the secondary
bowl has a more constant pressure and maintains a better air/fuel
mixture for the cylinders feeding from the secondaries.
The extra squirter can help you tune out wide open blasts on the
secondary side as well.
drive wide open for long periods of time.

The obvious benefit of the dual fuel line is that you have equal inlet
pressure at each bowl instead of the rear feeding from the front line.
You may notice an improvement on the drag strip as the secondary
bowl has a more constant pressure and maintains a better air/fuel
mixture for the cylinders feeding from the secondaries.
The extra squirter can help you tune out wide open blasts on the
secondary side as well.
Joined: Mar 2000
Posts: 43,187
Likes: 43
From: Littleton, CO USA
Car: 82 Berlinetta/57 Bel Air
Engine: L92/LQ4 (both w/4" stroke)
Transmission: 4L80E/4L80E
Axle/Gears: 12B-3.73/9"-3.89
Since you have a T5, the double pumper is the better choice. Throttle opening will be a direct correlation to accelerator pedal movement, which isn't the case with vacuum secondary or air valve type carbs.
Thread Starter
Member
Joined: Oct 2007
Posts: 123
Likes: 0
Car: 1986 Trans Am
Engine: 350 4BBL
Transmission: T5
Axle/Gears: 3.70
Re: Double pumper Q's
Great, thanks for the info. I went out today and bought a rebuild kit for the carb so as soon as the car comes out of storage and I can work on it I will be doing the rebuild. It leaks fuel anyway so I figured I should just replace everything with new parts. So I'm sure you will see some post's from me on that subject haha...... I just got done looking at my rebuild kit and the instructions make it look a little itimadating (sp?) especially with all those small washer like gaskets...and as for the instructions all there is is an exploded view of the carb all tore apart.
Last edited by valleyguy; Apr 9, 2008 at 03:33 PM.
Joined: Mar 2000
Posts: 43,187
Likes: 43
From: Littleton, CO USA
Car: 82 Berlinetta/57 Bel Air
Engine: L92/LQ4 (both w/4" stroke)
Transmission: 4L80E/4L80E
Axle/Gears: 12B-3.73/9"-3.89
The numbers in the exploded view are the order for disassembly. Assembly starts with the larger numbered parts down to the lower numbered parts. Adjustment details are on the following pages.
Thread Starter
Member
Joined: Oct 2007
Posts: 123
Likes: 0
Car: 1986 Trans Am
Engine: 350 4BBL
Transmission: T5
Axle/Gears: 3.70
Re: Double pumper Q's
I read through the instructions and got the gist of what the diagram was showing but holy there is alot of little parts...I can see some spare parts layin on the table after this job..lol
Joined: Mar 2000
Posts: 43,187
Likes: 43
From: Littleton, CO USA
Car: 82 Berlinetta/57 Bel Air
Engine: L92/LQ4 (both w/4" stroke)
Transmission: 4L80E/4L80E
Axle/Gears: 12B-3.73/9"-3.89
I put an old bath towel on the workbench. Part #1 goes in the upper left corner of the towel, #2 to the right of it, so on across the top of the towel. Then start a new row if necessary on the left side again, etc. Assembly starts at the lower right moving to the left & up. I leave parts that will be replaced in their place in the order, and when the new kit part goes in, the old part goes to a can off to the side (don't throw them away until the whole thing is together and running).
Trending Topics
Thread Starter
Member
Joined: Oct 2007
Posts: 123
Likes: 0
Car: 1986 Trans Am
Engine: 350 4BBL
Transmission: T5
Axle/Gears: 3.70
Re: Double pumper Q's
Sounds like a good idea, thanks for the tip. I think if I can find one I might pick up one of those holly carb books I think it has more detailed tear down info and has alot of tunning info as well....I would like to learn as much as possible before I tear into it that way I'm not wondering what this part or that part does.
Thread
Thread Starter
Forum
Replies
Last Post
skinny z
Engine/Drivetrain/Suspension Parts for Sale
5
Oct 5, 2015 06:23 PM






