Rough idle when cold

[Ed]

I pull the choke back about 1/2 way and she starts just fine. If I drive her right away she will buck a little and run pretty rough. After she warms up she runs great, idles at about 800 rpm. No choke needed to restart.

Some of the modifications I've done:

MSD 6AL ignition and blaster coil. Which made a huge improvement.

81 ZX distributor with the 12-80 module.

The carbs are Ztherapy rebuilds (about 7 years old and +-30k miles).

Mild grind cam with a 270 duration. Done by delta cam.

No clue which needles are in the carbs.

I'm trying to improve my idle while the engine is cold. I feel I have to baby sit her while she warms up. Giving a bit of throttle every now and again, lowering the choke.

The carbs have been recently balanced and my air/fuel is about 12.5:1

Any suggestions?

Ed

[beandip]

Sounds like a normal well tuned carbed engine. Other that installing a injection system and computer to do the thinking for you , things sound like every thing is as good as it gets. Gary

[justaZcarguy]

That is exactly how mine behaves, I think that I could use a dialing in, but other than that I agree with Gary that it is what it is.....

[BuDavid]

seems normal to me:rolleyes:

[Arne]

My all stock '71 is exactly the same. Cold running is not so hot (pun intended). This is why they designed them to have a hand throttle. To bad the Feds didn't understand.

[naviathan]

Try adjusting the choke as it bucks and see where it smooths out. More than likely it's either getting too much or not enough fuel for the cold start. But really it is just the nature of a carburated engine when cold. The fuel air mixture on a manual choke is very difficult to keep straight. With electronic chokes they slowly release as the engine gets warmer keeping from getting too lean or too rich.

[Ed]

Thanks guys, I kind of figured as much. Good to hear that it's normal.:classic: