Holley carb adjustments

[DanoDMano]

Since installing my K&N filter I have had several carb problems. The choke does not work correctly anymore, and It seems sluggish and backfires when starting cold.

Is there a Lean adjust or air/fuel adjustment?

Does anyone have a drawing or image that shows the different adjustment screws?? It is a 600CFM, maybe a couple years old. I bought it from MikeP a board member that relocated and hasnt been on the sight for awhile.

Any help would be greatly appreciated!!

[Paul72]

to adjust your choke, start with a cold engine. Crack the throttle to set the choke. Loosen the 3 screws that hold the cap on and turn the cap to close the butterfly, and tighten the screws.

There are 2 idle adjustment screws on the metering plate (the vertical plate right behind the fuel bowl), adjust these in/out until you get maximum vacuum.

Most likely you will have to go up a jet size or two. You've got more efficient air flow, so you need to up the fuel delivery to match. The good news is that you'll be making more power!

I'll try to find a pic or diagram for you.

Paul

[70short/step]

DanoD,
The only adjustment screws are on either side just behind the front float bowl. These two screw are only for idle upto about 1200 to 1500 RPM. Start your truck and you will have to idle it up to adjust them turn them in all the way and quickly turn them outward 1 1/2 times. That is where you should start for the fine tuning. Then start turning each of them (one at a time) in either direction, until the idle is smothest and the RPMs are the highest. Once done if this doesnt fix your problem that your having, You may need to change the jets either up or down. Those are not adjustable and you will have to buy different sizes. Check your plugs and see if they are running rich after you adjust idle crews mentioned above. If they are running rich then use smaller jets. Running lean, bigger ones. Hope this helps.....Short/Step

[DanoDMano]

Hey Paul, when you say crack the throttle, does that mean put it to the floor or just open it up a little?? I noticed the there is a loop at the end of the choke coil or element inside the choke. The arm that is connected to the lever for the butterfly goes inside this loop correct??

Should there be a lot of tension when I rotate the choke housing, because there doesnt seem to be alot??

Thanks for your help Guy's!!

[Paul72]

You can put the throttle to the floor one time and that should set the choke.

The loop at the end of the spring does control the butterfly. There shouldn't be much tension in the spring - as it warms up the spring relaxes, opening the butterfly. Turn the cap just enough to close the butterfly.

Also, if it is backfiring through the carb - it's running lean.

Another thing to check is the float level. There are screws in the side of the float bowls. The fuel level should be at the bottom edge of the hole. Adjust the level by loosening the screw on top of the bowl and turning the hex (5/8" I think). Do this with the engine running.

[DanoDMano]

Man I love learning!!

With the choke being electric I obviously need to be running during all this?? What does the 12v do for the choke if the coil reacts to temperature??? Is there some form of switch, or element??

[miket]

Dan,

I had an electric choke on my 870. For the life of me I could not get it to work properly. However it was probably my fault. I did send you an email with a word doc that might help. If I recall the the coil heats up enough to move the butterfly and you have to make sure there is vac/air getting into the coil housing.....there is a pin hole I believe on the bottom. I sent you a pic of the fast idle screw setting. I have some jets if you think you might need to rejet.

Good luck.

By the way yahoo rejected your the email I sent you.

[DanoDMano]

Thanks for the email Mike! I wont be at work until tomorrow but I'll check it out!! Then wierd thing about it is the thing worked great before I put the K&N on?? Probably just a coincidence??

[miket]

Originally posted by DanoDMano
Thanks for the email Mike! I wont be at work until tomorrow but I'll check it out!! Then wierd thing about it is the thing worked great before I put the K&N on?? Probably just a coincidence??

Could be extra air flow...maybe something got knocked outa whack? Could be running too rich/lean....

The doc is on the CGTCW website under files in the tech info folder.

[zeeklu]

This is a good Holley tuning site. http://www.bob2000.com/carb.htm Chris

[ddsmith]

The electric chokes are typically designed to function with a fully functional heat stove. Unfortunately they are normally long gone. In a correctly functioning system, the 12v that goes to the electric choke causes full choke off in about 1 1/2 to 2 min. If you think about that, you quickly understand why electric choke vehicles without the heat stove frequently have cold run problems. If the stove is still in tact there is a thermostatic valve on the air cleaner housing which causes a air valve to shift and draw air from the heat stove which is warmed by the exhaust manifold. The exhaust heats up far quicker than the engine. This provides warm air to the carb so when the electric choke comes fully off the warm air ensures proper fuel atomization. The thermostatic valve modulates the air valve to keep somewhat warm air going to the engine. Not necessarily the best thing for horsepower but very good for cold engine operation.

[Paul72]

The 12 volts are run through the spring, causing it to heat up. The spring is a bi-metal strip, meaning that one side heats up faster than the other (causing the spring to unwind - opening the butterfly). When the key is turned off, the spring cools off, causing it to wind up again, closing the butterfly.