[Trav]

after tuning with accelerator cams on my holley 750/ vac. sec. i found the perfect cam.. runs a little rich.. ( blows little bit of black when i stomp on it) other then that its got a bit more better throttle responce and so on.. but wut i noticed is at idel it really stinks.. smells rich.. this has nothin to do with the cam gear right? concidering its only effects the throttle?? would the air screws be wut i wana adjust here? im thinkin thats wut affects idle to 2000 rpm?? not to sure.. any advice would be nice.. thanx guys

[lluciano77]

Idle has nothing to do with pump cam. I don't think the black smoke has as much as you think with the pump cam either. I like to use the smallest cam and squirter I can without having a bog. I keep going down on cam size untill I get a bog, and then go up one size. Squirters are a little trickier to tune, but I like to do them after I pick the cam. Are you tuning with a Vacuum guage? If not, you should buy one. The money you will save in gas mileage will pay for it. It should eliminate some of that black smoke.

[Trav]

yes i do have a vacum gage.. but how do u use it with tuning a carb?? never done that before.. just with timing.. and i no wut u mean with the cam sizes.. i had one that boged real bad,, then next one was perfect.. and as for squirters... how can i tell wut size mine is now.. if i took it out are there #'s on it? then i go and buy a couple.. then trial and error from there? thanx again

[lluciano77]

You hook the vacuum guage up to a full time vacuum source. I like to set my throttle position so that my primaries are just slightly open, and then raise or lower my idle by the secondaries. This allows the mixture screws to be most effective. Then, you want to get the leanest highest manifold vacuum that you can with the mixture screws. I like to go a little rich and then lean each screw slowly untill the vacuum drops, and then richen up 1/8 of a turn.

Look in a Holley book or website and see what cams deliver what amount of fuel at what times. They are color coded. The squirters are stamped on their sides . You can see the numbers when they are on the carb. I wouldn't buy squirters yet untill you get closer with the cams. I like to get the cams right first.

[Wrencher]

Trav, if you used a vac. gauge to set your timing, you should recheck that also, set it with no vac advance!and a light.

[Tech @ BG]

When setting the idle on a carburetor there are a few things that should be done before making any adjustments.

-First verify that your primary and secondary butterflys are set where your carburetor manufacture wants them, if you have too much of the transfer slots exposed this will cause you to have a rich idle, and poor adjustment on your idle mixture screws.

-Double check your initial engine timing, if it is too low this will cause your engine to idle rich, and have poor throttle response.

-Check that your float levels are set properly if they are too high it will cause a rich idle condition

- Now you can start to adjust your idle mixture screws to get you best idle quality, and vacuum.

[hotwheels55]

What the BG tech is suggesting is what cured the problems I had in my ROAD DEMON on my ZZ4. Take it from him, follow his suggestions step by step and you'll resolve the rich idle, black exhaust, eye burning condition.
You can download the DEMON step by step procedures from their website...it'll apply to almost any type of carburetor, especially a HOLLEY. Take it a step at a time, don't try to do several issues at once or you'll never learn.

[Smoked Rubber]

Just recently I had a Similar problem with my 68 Chevy C-20 Pickup Running really rich, The engine would bog down or die on cold days, And The tail pipe really reaked of fuel. On warm days the Truck just had the heavy fuel smell, But it would pretty much idle and not die out. In both hot or cold conditions When I would stomp the accellerator down more then a quater way it would get really rich and bog down.

(The engine moped so I knew the timing was off already)

As soon as I went to adjust the timing I found out it was off by 6*. I advanced it, Now it run's perfectly. Just a suggestion, check the timing?

All you need is a Timing light and To know how many Degrees of Timing to add, and you're good to go.

If this isent whats wrong then sorry, Just trying to help

[Jmark]

Originally posted by lluciano77
I like to set my throttle position so that my primaries are just slightly open, and then raise or lower my idle by the secondaries. This allows the mixture screws to be most effective.

Hmm, thats a new method on me! LOL Is this a "Holley" thing? Can someone 'splain it a little better.

Seems like opening the secondaries up at idle will just give you a big vacuum leak and kill the idle quality, having the rear of the carb passing basically air with no gas mixed in, and the front of the carb passing a good mixture.

Mark

[hotwheels55]

Maybe he's looking at the carburetor backwards.

There's plenty of suggestions on automotive sites that won't work for anyone but the person who suggested it.

[1BAD80]

If an automatic set the vacuum while its in gear, just have someone hold the brakes on.

[lluciano77]

You get a better transition by reducing the primary opening. Opening the secondary butterflies a little doesn't cause a vacuum leak. You need the secondaries open to keep the idle circuit within range. All Holley 4150/4160s have a secondary idle circuit that is adjustable. Using it makes it that much better .

My car is an automatic. I never it in gear to adjust the mixture. I adjust it in park. I set it to highest vacuum and then give it 1/8 of a turn extra on each screw. 1/16 on my 4 corner carbs. When everything is adjusted the way I do it, I only loose 50 RPMs when shifting from park into drive. What that means is that it is set as on the money as you can get.

[Tech @ BG]

Open the secondary butterflies can help lean the idle circuit back out if you have the primary butterflies open too far.
Normally on mild street engines this is not needed (engines that idle under 1000 RPM) If you're working on a more radical engine, that has low engine vacuum at idle, air velocity, or an engine that idles over 1000 RPM you will need to open the secondary butterflys up to the same amount as the primary side. This will allow you to have less of your transfer slots exposed, pulling less fuel, and giving you better control on your idle mixture screws. This is the same reason why people will drill holes in the butterflys of the carburetor, it will allow you to close them further exposing less transfer slot (less fuel) but still give you the same idle RPM.

[TurboS10]

Originally posted by lluciano77
All Holley 4150/4160s have a secondary idle circuit that is adjustable. Using it makes it that much better .

Well the confused smilie is just perfect here, because you are just that. Most 4150 and all 4160 Holleys do not have a secondary idle circuit that is adjustable. I have owned one race prepped holley that is on my 57 that has adjustable secodary idle. Every other one has not. I can not tell you which models off the top of my head have the adjustable idle, but most if not all factory 4160's do not since they have no metering block installed. Like BG Tech outlined above, this is the main reason why opening the secondaries on a fat cammed engine helps with adjustability. A larger cam engine likes a leaner idle. For small cam engines the primary side can be easily adjusted without monkeying with the secondaries.

Chris

[Tech @ BG]

Actually all Holley 4150/4160 style carbs have a set screw to adjust where the secondary butterfys are set at idle. It is int the baseplate from the bottom side facing upward. You have to remove the carburetor to adjust this. If you remove that screw and install an allen headed screw from the top you can adjust these very easily.