Holley carb help

[dave73]

On a cold startup, the engine fires with 2 pumps of the gas pedal, then after about 10 seconds it stumbles like it's going to die. I can blip the throttle and it raises up to the high rpm idle setting and will die down on it's own after about 1 minute or so. Issue is, when I blip the throttle, immediately following there is a light colored smoke that smells super rich that comes out of the exhaust. Once the car is warmed up, it goes away. The runs fantastic when warmed up.

Setup is a 440 with a holley 850 double pumper and electric choke. Carb was fully rebuilt, specifically for my motor by a very reputable shop. Everything is brand new and has 400 miles on it.

I've attempted to solve the issue myself but I'm stuck. I adjusted the electric choke dial towards lean, thinking it's too rich on startup but that doesn't seem to make a difference. I've started with and without the air cleaner, with no change so air flow doesn't seem to be an issue. I've attempted to adjust the timing, but any adjustment makes it want to die. What else should I be doing? Thinking about putting on a fuel regulator and pulling plugs to see what they look like.

[Cuda Cody]

850 is a big carb!!!  It sounds like it might be choke related, but not 100% sure.  Why are you running a carb that big? 

[dave73]

Motor is a 440 stroked to 512, 10.5:1 compression, lunati hydraulic camshaft, aluminum heads and intake. A lot of guys are running 950's on the setup so I thought mine was being reserved?

[Cuda Cody]

That's a lot of engine so maybe the 850 is perfect for it.  I normally only play with stock stuff so it seemed like a lot to me. 

Do you have any other carbs you can try to see how they run?

[303 Mopar]

Motor is a 440 stroked to 512, 10.5:1 compression, lunati hydraulic camshaft, aluminum heads and intake. A lot of guys are running 950's on the setup so I thought mine was being reserved?

I ran an 850 Proform on the 505ci stroker, similar build to yours.  Seemed to be a good fit for that engine.  Dialing in the carb takes time and testing, maybe you need to drop down in jet size. Hopefully @Chryco Psycho has some tips.

[Shane Kelley]

Jetting won't have anything to do with it. Main jets don't come into play till around 2000 rpm. Give or take. Your dealing with the idle circuit below 2000. I would try backing the idle mixture screws out on the metering block a 1/4 turn and see what effect that has. Check your float levels also but I doubt that's your problem unless it's flooding out. Something to remember is a big cam motor running with a carb will rarely ever be perfect all the time. Just how it is! That's one of the big reasons guys are moving to EFI. 

[bennydodge]

Had a similar problem with the 870 avenger on my stroker 416. By the time it was right the choke was almost completely dialed back-second to last notch(lean) on the choke cap. Mine did the same thing with the white smoke. Once the choke was right it cleared up completely. Make sure the choke is closing correctly and that it's opening slowly and smoothly. I fiddled with it a LOT before it was close.

[RUNCHARGER]

It sounds like the choke is hanging up to me. You shouldn't have to blip the throttle to get it to catch high idle after it starts. So I would check for a lever or the choke blade rubbing. To me it sounds like it is sticking going on and sticking coming off choke.

[Chryco Psycho]

Motor is a 440 stroked to 512, 10.5:1 compression, lunati hydraulic camshaft, aluminum heads and intake. A lot of guys are running 950's on the setup so I thought mine was being reserved?

I agree you are on the smaller side with an 850
I assume you have full 13 v at the choke , , if you are getting smoke it has to be rich side  you should need to use less choke / leaner setting as you have tried , it may work better without the choke at all just dial it right out so it cannot come on , generally I set them so they barely close at around 60* F  when I do use them

[dave73]

I'll try moving the choke dial further toward lean as a few of you have recommended. I only moved it 2 notches from the center mark so far.

Just for clarity, as I'm finding some conflicting details on the web the more I search, spinning the dial clockwise leans the choke and counterclockwise richens the choke?

[Shane Kelley]

I'll try moving the choke dial further toward lean as a few of you have recommended. I only moved it 2 notches from the center mark so far.

Just for clarity, as I'm finding some conflicting details on the web the more I search, spinning the dial clockwise leans the choke and counterclockwise richens the choke?

Just watch the choke blade when your turning it. Richer is closed more and leaner is opened more.

[dave73]

Just watch the choke blade when your turning it. Richer is closed more and leaner is opened more.
[/quote]

The choke blade doesn't move at all as the black dial is rotated, neither clockwise nor counterclockwise.

[bennydodge]

All's the cap does is control choke timing, leaner comes off faster and richer stays shut longer.