Newbie: Engaging Choke

[jforest1]

So reading through the instructions for adjusting idle fuel mixture for my carb (in my signature), and 1st step is to engage the choke.  I picked up somewhere that I do this by ?revving the engine momentarily at WOT?  Is that correct?  If so, idle RPMs seem to slowly work their way back up.  Is there a better way to engage choke?

JF

[Chryco Psycho]

with the engine cold & not running open the throttle 1/2 way & it should close

[jforest1]

How long will it remain closed?

Also, how will I engage it when the engine is warm (1st step of adjusting idle is to run the engine for ~10 minutes).

JF

[beekppr]

If your simply trying to set the fast idle speed (the speed when it's cold and warming up) then I would adjust it cold.

Unless it is electric, it should stay engaged until the engine warms up and you rev the engine. Either way, I'd chk it cold, and if you want it higher or lower in speed, shut it off before it warms up and make a quick adjustment. Some carbs have a screw, others like my holley have a small tab you twist to get it to lock plastic the choke cam (for lack of a better description).

If you are trying to adjust how much choke is applied when cold, then I'm not sure how the Edelbrocks work. On many carbs, there is a small rod you can tweak to get the choke to open or close more depending on need.

Hope this helps

[Chryco Psycho]

electric chokes have a bi-matallic strip in them & you can rotate the housing so the choke comes off faster or slower , for most of these cars they do not get driven in cold weather so I turn them so they barely come on & come off very quickly to prevent fouling plugs & wasting fuel

[jimynick]

JF, you've got a variant of the old Carter AFB/AVS. You DON'T want to engage the choke to set idle speed unless it's the cold idle speed. When you whack it open, the unloader pushes the choke off the choke cam, but if the engine isn't warm enough, the thermo spring mentioned will push the cam that controls choke position and cold idle speed back together and a partial throttle will allow the linkage to jump back into the full or partial position and increase the idle speed. If you simply grab the choke blade with one hand and pull it wide open, you can then give the throttle a blip and the fast idle cam will disengage and the idle screw will then be on the regular idle cam. It sounds much more complicated than it actually is and a few minutes studying the linkage positions with the choke both in open (disengaged) or closed (engaged) will help you see what's going on. The choke/fast idle cam usually has 2-3 steps for varying cold idle speeds at the same screw setting and in a perfect world the choke would pull off sequentially onto these steps until finally, nice and warm, it pulled onto the regular idle cam and just loped away. Hope this helps.

[jforest1]

 

I'm gonna need some time to digest these posts.

I've read through the carburetor manual twice, and get the basic theory behind it, but it seems a bit tough to learn this one on my own.  Perhaps its just late...

JF

[beekppr]

I've been there on many different things. I know the feeling. I find that if I take the time to study the mechanics of how something operates and then mull it over a few days, things start to fall into place.

If you make a change, see how it operates and if it is worse, try to correct it first before changing a second thing. That's not laways the case but it works better more times than not.

[jimynick]

JF, I went back and re-read your initial post. You mention adjusting the idle fuel mixture rather than the idle speed; my apologies. To set the mixture make sure the engine is warmed fully and idling normally, choke fully off/open. It's best to use a tach/vacumn gauge, but the old MkI ear works too. The basic rough setting has usually been 1 1/2 turns of the adjusting screws out from being fully run in on their seats. seat the screws-gently and don't force them and then turn them out as noted above. Fire the engine and slowly turn each screw in 1/8th of a turn at a time and wait for 30 seconds listening for any rpm/vacumn increase. Continue doing this until the engine starts to stumble or the rpm dies down and then turn the screws back to the last setting where the engine ran the fastest/best vavumn and leave them there. You may have to turn down the idle speed screw while adjusting the mixture screws as sometimes the rpm will increase too much for the engine to stay on the idle circuit in the carb. The basic idea is to obtain the best rpm and vacumn by adjusting the screws within their range. If you turn the screws all the way in and th engine doesn't change or stall, you need to rebuild the carb, it's bunged. Carters are easy carbs to work on, you'll get there.

[jforest1]

Just want to thank everybody that posted on this.  I definitely didn't get most of what you guys were posting about.  The carb manual from Edelbrock is not enough for a newbie.  HOWEVER, any other newbies out there reading this may benefit as I have from:

How to Rebuild and Modify Carter/Edelbrock Carburetors

It has very thorough explanations of how carburetors work, color pictures, and diagrams; most importantly, after reading 1/3 of it, I now understand these posts above. 

JF

[Bullitt-]

This may help... http://www.streetfire.net/video/Fast-Idle-Adjustment_159113.htm