The engine runs great, but the idle speed changes as the engine warms up. It idles low enough when it is cold that I have to use the choke to keep it running. (regardless of the ambient temp outside.) It starts at about 500 rpms when it is cold to about 1000 rpms when it is up to running temp. The carb is an Edlebrock 1405. Hmmm, my old Harley does the same thing. Thanks Kevin

When you say "have to use the choke", it sounds like you're using a manual choke. One thing a choke does is raise the idle speed. Sounds like your base idle is set too high and the stepped idle cam on the choke isn't adjusted properly.

I don't recall if my manual choke had the idle speed cam assembly, but I think it did. Seems like I robbed it when I installed my electric choke. If yours choke setup has it try this. If not, then I'm full of prunes.

Close the choke and tap the accellerator pedal to set fast idle. Then start the motor and pull off the choke as needed to keep it running. Adjust the fast idle screw to get your idle up where you need it to be for a cold motor. Cold idle speeds of 1200 to 1800 RPM are common. warm it up good then set the idle speed. 800 RPMs is good for a street motor. 1000 RPMs or more may be needed for a cammed up motor with no bottom end.

Anytime you start the motor, be sure to push the choke in, tap the accellerator pedal, crank and play with the choke. Just don't leave the choke near fully closed too long if the engine won't fire. With a manual choke, you are the pulloff and you can flood the motor quickly if you don't pull off.

Put the prunes away, it does have a fast idle cam. The only reason I need to use the choke (for the fast idle cam). By the time I get it out of the garage it idles fair enough, to stay running, and I can deactivate the choke. I was hoping for a hot idle of about 800 rpms but that would mean it would idle at 300 when cold. My Harley has a SU carb (no choke) and has been idleing like that for 25 years. It's nothing I can't live with but was just curious about what would cause it. Thanks Kevin

Its normal, set the idle speed when the engine is warm where you want it, use the choke to keep the engine running when its cold. Thats how carbed cars work, theyve been that way since the first cars with carbs where produced. Even engines with EFI have a choke function built in.

My 1405 does the very same thing. I have to keep the RPM's up till it warms up and then it idles fine. I have yet to put a choke on it.

Are you running full vac. or ported?

Put the prunes away, it does have a fast idle cam. The only reason I need to use the choke (for the fast idle cam).

Keep in mind that once you close the choke and tap the throttle, the fast idle cam is set. You then can pull the choke off and it will stay on fast idle until you tap the throttle again.

Sounds like your setup is working like it should. Just might need a tweak to get your cold and hot idle settings where you want. BTW, that fast idle screw is on the passengers side and a bit hard to get to. Sometimes a small 1/4" drive socket is easiest to get at it with the engine running.

I'm running ported because that's where it runs the best. I hear you about the FIS. It's a pain in the but I adjusted it anyway. I'm not saying that it runs bad for a long time. Only for about a minute or so till it cleans up. Kinda sounds like a an old C-47 when it fires. I'm going to set it hot at about 800 and live with the choke. Thanks Kevin

I hear you about the FIS. It's a pain in the but I adjusted it anyway. I'm going to set it hot at about 800 and live with the choke. Thanks Kevin
As dnult suggested and I will too, set curb idle with engine hot to your desired rpm. Turn engine off, open up throttle to WOT, and adjust the fast idle screw for fast idle, close throttle onto fast idle cam, start engine to check fast idle rpm.

Setting fast idle is quickly done with WOT.