Carb question

[wickedwelder]

I have an 85 suburban with 350 running a two barrel carb. The problem im having is that now that its getting cold in the mornings it doesn't want to stay running. Some mornings it does great but others it acts like its running on 4 cylinders, smokes the neighborhood out and then floods it self out within a matter of minutes. Is this being caused by the choke not working right? If so how do I adjust it so it'll run no matter how cold? If the problem lies somewhere else where would I look? If its the choke why will it work some days but not others?
Thanks for your time

 

[76zimmer]

I have an 85 suburban with 350 running a two barrel carb. The problem im having is that now that its getting cold in the mornings it doesn't want to stay running. Some mornings it does great but others it acts like its running on 4 cylinders, smokes the neighborhood out and then floods it self out within a matter of minutes. Is this being caused by the choke not working right? If so how do I adjust it so it'll run no matter how cold? If the problem lies somewhere else where would I look? If its the choke why will it work some days but not others?
Thanks for your time

sounds like the choke isn't opening...the choke plate should snap close when the engine is cold (like overnight) and I assume its electric? Depress the throttle twice before turning the key on, and start...it should crack open about 1/8 inch immediately and then slowly open over the next 5 min or so until it is fully open by the time the engine is 150* or so.

Got a pic of the carb setup...a 2bbl isn't stock.

 

[wickedwelder]

Normally pumping the throttle twice works but when it doesn't nothing works. It just refuses to stay running.
What carb should be on there?

 

[dremu]

What carb should be on there?

Four-barrel Q-jet, prolly computer controlled in that era.

-- A

 

[76zimmer]

my 85 had a carb with the electrically controlled enrichment??? in the front...unplugged it, never felt any different. so a properly tuned electric choke Qjet should work I think. My 85 only had computer Electronic Spark Control (retard) on it

 

[diesel4me]

Many 70's GM V8's had 2 barrel carbs,there is nothing "wrong" with a good one,I'd keep it on there,you'll get better mpg's and better low end torque with one than most 4 bbl carbs, (Q-jets are an exception because they have small primary barrels smaller than some 2 bbl carbs did...)..........................................................................................................................................................................................................You may have a spring type choke thermostat that sits on the intake instead of an electric choke,there are other styles also,you'll need to find out what you have...if its not opening the choke soon enough after it warms up some it might flood or run rich and blow sooty black smoke out of the exhaust...another possibility is the choke pull off may have failed ,its a vacuum diaphram dewhickey on the carb that uses vacuum to open the choke butterfly some as soon as it starts,if it doesn't,it'll load up and stall,flood out,run too rich,etc...it has to be adjusted right so it opens the choke just enough so it wont do that,or run too lean if it opens it too much and make it bog and stall out.............................................................................................................................................................................................................I've had several carbs that liked to ice up on frosty damp mornings,the engine would shake and stumble like someone pulled sonme plug wires off,and often stall when you let off the throttle...you could actually see the frost build up on the carb body,and GM designed a air cleaner with a heat stove and a "door" that was supposed to close and deliver heated air to the carb to prevent this,it worked in conjunction with an exhaust heat riser valve that closes when cold and sends the exhaust from the passenger side bank thru cast passages in the intake manifold to heat the base of the carb up to improve fuel vaporization....since many engines have had these things "deleted" when aftermarket exhaust or intakes and carbs get put on,these symptoms become evident and can be hazardous if it affects cold driveability enough...like having it stall when your coasting down a hill and the power brakes go away,and the power steering!...

 

[wickedwelder]

I'll get some pics posted tomorrow of the carb on it now(traveling today) yesterday I went out to the jy and found a q-jet 4 barrel but not sure if all the pieces are on it. I need to find some pics if one and then go double check. Also found an edelbrock 4 barrel still on a 78 gmc 1/2 ton.
Which would be the better one to try? They both need rebuilt but was wondering which is better. I've always heard that q-jets aren't very good hence the nick name q-junk. I've never run one before, I've run holleys and motorcraft in the past on some old fords but this is my first gm vehicle.

 

[diesel4me]

Everyone has their favorites,I prefered Carter AFB or Edelbock carbs over a Q-jet,they seem to give a bit more power and dont have the issues Q-jets had with leaky well plugs and not being the most user friendly carb to set up properly...that said,they DO work very well once you get them dialed in properly and will give better gas mileage than most other carbs if you keep your foot off the pedal and dont boot in the secondaries too often..................................................................................................I've gotten 15 mpg out of Edelbrocks on 350's,and they seemed more peppy than they were VS the stock Q-jet,some off road enthusiasts dont care much for them because they tend to flood easily if bounced around and when your climbing or descending steep grades or running off-camber--they sell special needle & seat kits to help offset that,but they dont always help in certain conditions...a Q-jet will practically run an engine upside down without faltering,giving it the nickname of "poor man's fuel injection"--I rarely go off road ,I liked the Edelbrocks,but I noticed my plow truck that had one would stumble and stall out if I climbed up a snowbank too high with it....it didn't like steep hills--otherwise it was a great "street" carb,and they are pretty simple to rebuild too.....................................................................................................I've had several Holley carbs and most of them were nothing but greif,one caught fire and darn near roached my '72 K5,and they always seemed to need constant fiddling with mixture adjustments when the weather changed,the power valves often blew out if they spit back on a cold morning when I opened the choke too soon,and I came to hate them after awhile!..only ones I had good luck with were a model 4360 "Economaster" 4 bbl (450 cfm) and a few Economaster 2 bbl ones I had on a 307 V8 and a 283 I had in a '67 Impala..they gave good performance and I got up to 18 mpg with them....