Jackfit

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

tbarb

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.

65tripleblack

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.

Jackfit

Hi, just the info I needed. I have put on Allen screw with loctite, came with trick kit.

Thanks all

Jack

tbarb

After you get it all happy don't forget to double check the emulsion screw adjustment again last.

Remember, opening and closing the secondary all you are doing is giving more air because the transfer slot on the secondary side is higher.

MelWff

i was under the impression from the factory shop manual the secondary stop screw is adjusted a 1/2 turn from fully closed which exposes the secondary transfer slot the correct amount.

tbarb

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.

Jackfit

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 ......

PAmotorman

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

65tripleblack

Also make sure that the idle air bleeds are open and clean.