Holley Idle Question
Thread Starter
Le Mans Master
Joined: Feb 2006
Posts: 5,073
Likes: 414
From: Maine
Holley Idle Question
Hi, I have a question for Holley people.
1966
L-79 327/350
Original Engine
Comp Cam 256 Update
Flat Top 9.5 + compression
Original Heads Hump 2.0 valves
.060 over
380lbs + dyno torque 5,200 rpm
16-18 vacuum gauge at 850-900 idle
Holley 3367 4160 Stock Carb Man Choke Original replacement
7.5 Power valve .65 jets
10* int 12* VC 49* @ 2,200 all in 52* at 3,000 rpm
I keep my idle at 850-900 rpms as standard ......
My question is on setting the idle with the secondary throttle adjustment screw...
How little idle do you want with your primary idle adjustment screw.
Can I have all idle with the secondary adjustment (850-900 rpm) with the primary throttle full shut?
Or do I get close to the 700 rpm with the Secondary and add a little primary throttle.
I know about the secondary slots and how much to show....I have rebuilt the carb and know it....just trying to fine tune it. Car runs great now after distributor rebuild.
Basic question...All idle by secondary or A little of both....
Jack
1966
L-79 327/350
Original Engine
Comp Cam 256 Update
Flat Top 9.5 + compression
Original Heads Hump 2.0 valves
.060 over
380lbs + dyno torque 5,200 rpm
16-18 vacuum gauge at 850-900 idle
Holley 3367 4160 Stock Carb Man Choke Original replacement
7.5 Power valve .65 jets
10* int 12* VC 49* @ 2,200 all in 52* at 3,000 rpm
I keep my idle at 850-900 rpms as standard ......
My question is on setting the idle with the secondary throttle adjustment screw...
How little idle do you want with your primary idle adjustment screw.
Can I have all idle with the secondary adjustment (850-900 rpm) with the primary throttle full shut?
Or do I get close to the 700 rpm with the Secondary and add a little primary throttle.
I know about the secondary slots and how much to show....I have rebuilt the carb and know it....just trying to fine tune it. Car runs great now after distributor rebuild.
Basic question...All idle by secondary or A little of both....
Jack
Safety Car
Joined: May 2014
Posts: 3,790
Likes: 661
What you want is to open the primary throttle blades so you can barely see the transfer slot (.010-.015) then adjust the secondary throttle blade stop screw to set the idle rpm then adjust the emulsion screws for best vacuum or idle.
If you need to readjust the idle use the secondary screw and don't touch the primary side. You can remove the secondary screw and go to home depot to get a allen head screw so the adjustment can be made without removing the carburetor.
If you need to readjust the idle use the secondary screw and don't touch the primary side. You can remove the secondary screw and go to home depot to get a allen head screw so the adjustment can be made without removing the carburetor.
Safety Car
Joined: May 2003
Posts: 4,797
Likes: 239
From: Ocean Township NJ
Secondary screw should have threadlocker on it. Sounds like it's been disturbed.
Secondary throttle plates should be slightly cracked open. Best way is looking for light with carb removed.
If carb is installed, back out adj screw till plates close, then turn clockwise until they are cracked open, about 1/4 turn.
Adjust transfer slots per above post.
Secondary throttle plates should be slightly cracked open. Best way is looking for light with carb removed.
If carb is installed, back out adj screw till plates close, then turn clockwise until they are cracked open, about 1/4 turn.
Adjust transfer slots per above post.
Last edited by 65tripleblack; Jul 19, 2017 at 02:16 PM.
Thread Starter
Le Mans Master
Joined: Feb 2006
Posts: 5,073
Likes: 414
From: Maine
What you want is to open the primary throttle blades so you can barely see the transfer slot (.010-.015) then adjust the secondary throttle blade stop screw to set the idle rpm then adjust the emulsion screws for best vacuum or idle.
If you need to readjust the idle use the secondary screw and don't touch the primary side. You can remove the secondary screw and go to home depot to get a allen head screw so the adjustment can be made without removing the carburetor.
If you need to readjust the idle use the secondary screw and don't touch the primary side. You can remove the secondary screw and go to home depot to get a allen head screw so the adjustment can be made without removing the carburetor.
Thanks all
Jack
Safety Car
Joined: May 2014
Posts: 3,790
Likes: 661
Remember, opening and closing the secondary all you are doing is giving more air because the transfer slot on the secondary side is higher.
Safety Car
Joined: May 2014
Posts: 3,790
Likes: 661
On a vacuum secondary carburetor the secondary transfer slot is made higher in the base plate. You don't want to expose that at idle (secondary side) or the engine will get rich. The factory adjustment is done simply so the throttle blades don't get stuck in there bores when closed, remember it's venturi vacuum that acts on a diaphragm to open them and nothing mechanical. The vacuum secondary throttle shaft has teflon bushings to allow a easy smooth opening.
Thread Starter
Le Mans Master
Joined: Feb 2006
Posts: 5,073
Likes: 414
From: Maine
Rich Idle
Hi repost of my specs, My car is running great 16-17 mpg at highway speeds...11 around town . M20 3:36
Question , rich idle......correct Holley...6.5 jets
But my Vac is about 18-20 at idle......because of my Comp Cam 256....
Seems rich.....smells rich.....do I need to change jets?
See specs
1966
L-79 327/350
Original Engine
Comp Cam 256 Update
Flat Top 9.5 + compression
Original Heads Hump 2.0 valves
.060 over
380lbs + dyno torque 5,200 rpm
18-20 vacuum gauge at 850-900 idle
Holley 3367 4160 Stock Carb Man Choke Original replacement
7.5 Power valve .65 jets
10* int 12* VC 49* @ 2,200 all in 52* at 3,000 rpm
I keep my idle at 850-900 rpms as standard ......
Question , rich idle......correct Holley...6.5 jets
But my Vac is about 18-20 at idle......because of my Comp Cam 256....
Seems rich.....smells rich.....do I need to change jets?
See specs
1966
L-79 327/350
Original Engine
Comp Cam 256 Update
Flat Top 9.5 + compression
Original Heads Hump 2.0 valves
.060 over
380lbs + dyno torque 5,200 rpm
18-20 vacuum gauge at 850-900 idle
Holley 3367 4160 Stock Carb Man Choke Original replacement
7.5 Power valve .65 jets
10* int 12* VC 49* @ 2,200 all in 52* at 3,000 rpm
I keep my idle at 850-900 rpms as standard ......
Last edited by Jackfit; Sep 13, 2017 at 08:47 AM.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
5 Best & 5 Worst Corvette Daily Drivers
Joe Kucinski
The Headlights of Every Corvette Generation Explained
Joe Kucinski
5 Best & 5 Most Overrated Corvette Track Packages of All Time!
Joe Kucinski
Every 2027 Corvette Engine Explained
Joe Kucinski
Designer Imagines A Corvette That Looks More Like a Corvette Than the Corvette
Verdad Gallardo
10 Ugly Corvettes That We Still Kinda Love
Joe Kucinski
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
Melting Slicks
Joined: May 2007
Posts: 2,415
Likes: 154
if you want to change the air fuel ratio at idle you need to reduce the area of the idle fuel restriction by installing pieces of .015/.017 diameter wire in the IFR. make sure the idle transfer slots are set correctly first and you are not idling off of the ITS
Safety Car
Joined: May 2003
Posts: 4,797
Likes: 239
From: Ocean Township NJ
Also make sure that the idle air bleeds are open and clean.