Double Pumper Tuning Help
Thread Starter
Pro
Joined: Sep 2004
Posts: 579
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From: North Texas
Double Pumper Tuning Help
I've just installed a holley 650 dp and have an idle problem!
I followed Lars setup exactly - using .020 on the primary butterflies and matching the "light" on the secondaries. I had to turn the idle mixture screws out 1 3/4 to get an idle at all but it dies after a few minutes and is running rich at idle - no choke.
When driving to stopping I can hear it change to the idle circuit then it starts running rough. While driving or WOT it is a BEAST!!!
Any help?? Thanks.
I followed Lars setup exactly - using .020 on the primary butterflies and matching the "light" on the secondaries. I had to turn the idle mixture screws out 1 3/4 to get an idle at all but it dies after a few minutes and is running rich at idle - no choke.
When driving to stopping I can hear it change to the idle circuit then it starts running rough. While driving or WOT it is a BEAST!!!
Any help?? Thanks.
Race Director
Joined: Nov 2000
Posts: 11,872
Likes: 12
From: Waterloo ontario Canada
I find all double pumpers too rich at idle. I would drill .090 holes in all 4 throttle plates, but they are to be drilled in an exact location . I would also install ,015 wires in all 4 idle circuits. I realize this might go over your head but this is really not hard, can be done in an hour easily, the carb must come off the motor and it will lean out the idle and make the car leaner throughout the entire range.
I do this to ALL my double pumpers. I like the carb just not the factory setup.
This is recommended by Holley.
I do this to ALL my double pumpers. I like the carb just not the factory setup.
This is recommended by Holley.
Melting Slicks
Joined: Dec 1999
Posts: 2,116
Likes: 156
From: Mid West
Cruise-In III Veteran
Originally Posted by norvalwilhelm
I find all double pumpers too rich at idle. I would drill .090 holes in all 4 throttle plates, but they are to be drilled in an exact location . I would also install ,015 wires in all 4 idle circuits. I realize this might go over your head but this is really not hard, can be done in an hour easily, the carb must come off the motor and it will lean out the idle and make the car leaner throughout the entire range.
I do this to ALL my double pumpers. I like the carb just not the factory setup.
This is recommended by Holley.
I do this to ALL my double pumpers. I like the carb just not the factory setup.
This is recommended by Holley.
Thread Starter
Pro
Joined: Sep 2004
Posts: 579
Likes: 0
From: North Texas
Originally Posted by norvalwilhelm
I find all double pumpers too rich at idle. I would drill .090 holes in all 4 throttle plates, but they are to be drilled in an exact location . I would also install ,015 wires in all 4 idle circuits. This is recommended by Holley.
Thanks!
Burning Brakes
Joined: Mar 2004
Posts: 816
Likes: 1
From: Finland
Originally Posted by Nate 76x
I've just installed a holley 650 dp and have an idle problem!
I followed Lars setup exactly - using .020 on the primary butterflies and matching the "light" on the secondaries. I had to turn the idle mixture screws out 1 3/4 to get an idle at all but it dies after a few minutes and is running rich at idle - no choke.
When driving to stopping I can hear it change to the idle circuit then it starts running rough. While driving or WOT it is a BEAST!!!
Any help?? Thanks.
I followed Lars setup exactly - using .020 on the primary butterflies and matching the "light" on the secondaries. I had to turn the idle mixture screws out 1 3/4 to get an idle at all but it dies after a few minutes and is running rich at idle - no choke.
When driving to stopping I can hear it change to the idle circuit then it starts running rough. While driving or WOT it is a BEAST!!!
Any help?? Thanks.
Thread Starter
Pro
Joined: Sep 2004
Posts: 579
Likes: 0
From: North Texas
vesa - go to http://www.corvettefaq.com/engine.asp
For your carb read under barry grant speed demon carb tuning - they are both mechanical secondaries and have a small difference but both are discussed here. Also browse this site, I have found A LOT af great info here.
For your carb read under barry grant speed demon carb tuning - they are both mechanical secondaries and have a small difference but both are discussed here. Also browse this site, I have found A LOT af great info here.
