Anyone got tips on leaning out a 2.8L chevy V6 stock carb?

Mine likes to blow BLAAAACK smoke out when I 'punch it' also, lately its been getting around 11mpg.... though, it fires up absolutely fantastic when its -20 or -30 F

sort by: active | newest | oldest
skunkbait8 years ago
Yep, that's probably running way rich. Check all of your plugs to make sure they are firing. If they are all equally black and sooty, they are running rich. Check the air filter. Then spray carb cleaner down the throat while the car is running (At idle, and at rev.) But really sounds like your choke may be partially stuck. It should be on the side, and is heat operated. If your choke is opening all the way up, and it's still acting that way, there are a few choices. A) Adjust (advance) timing slightly, as vehicle runs to make it backfire out the carb once or twice. (Not fully recommended.) B)Take carb apart (carefully) and clean all jets and valves. C)Play with mixture screw until vehicle behaves. Don't get it TOO lean, as this will overheat things badly. After running it for a while, recheck plugs to make sure they're not overheating and glazing up.
Junk_Wizard (author)  skunkbait8 years ago
I cannot find the mixture screw, it looks like i'm stuck buying a new carb for about ~200, sadly, that's worth more than the truck... I put the hottest plugs I could buy so they wouldn't foul up. I don't think it has a catylitic converter, its an 85... and it doen't have stock pipes. Airfilter is fairly new (also fell off once and didn't make a bit of difference besides making everything dirtier...) Timing is fine... right where I want it (stock) I know the choke isn't sticking because sometimes when I drop it into 3rd at 65 (to pass people on this one hill) the choke flops over and I end up doing 25 to the gas station and flop it back up.
The carb on that 85 is a mess even when it's working right. It is the last year and the only year for that carb. It was designed to keep pollution low and keep the Feds off of GM's back. There is a manifold and replacement carb that will straighten out that truck.But you are talking about spending about $550. and frankly it would be better to get rid of the beast, Fuel injection makes a big difference and by simply moving up two or three model years you will have a much better truck. That 2.8 engine is also an underpowered curse of an engine.
Junk_Wizard (author)  glorybe8 years ago
interesting... Got links?
Sounds like if you can't find a mixture adjustment, you're stuck rebuilding it or buying a new one. But, the fact that the choke flops closed concerns me a little. If it flops under accelerations, it might be slightly closing under normal revs. If you could wire it in the open position, just to experiment, you'd know for sure that wasn't the prob.
Junk_Wizard (author)  skunkbait8 years ago
yeah, but then i can't seem to ever get it started (i think its mostly pebkac) I guess i'll do it in the spring when I can ride my 650... I know i'll end up killing it in the rebuildand then buying a new one.
That sounds reasonable. DOn't attempt the trial and error stuff until you know you've got another way to get around.
Also, make sure catalytic converter is not restricted!
Hansj38 years ago
seafoam... if you can find it, its kind of a Midwest tradition. i have seen seafoam take an engine from almost dead to decent within a tank of gas. b12 chemtool might be more common though, but its nor as powerfull
Sandisk1duo8 years ago
do it carefully
Junk_Wizard (author)  Sandisk1duo8 years ago
What a terrible awnser, thats almost as bad as telling me to fill it with water!
but i didn't ell you to fill it with water : ) well, in that case use a dremel to buff all the crap off, then wipe it down with a rag clean everything you can see