[69elcaminoss]

My brother just picked up a 1984 Chevy shortbed truck with a 305 and 4 barrel carb. The truck is completely stock.

The problem is after idling for 5 minutes or so their is some greyish looking smoke coming out of the tail pipe. When you rev up the engine it goes away after a minute. Also, there is a strong exhaust smell when idling.

What has been done to this point.....
new air filter
new fuel filter
new spark plugs
sprayed a bunch of carb cleaner down the carb while running
put in a bottle of fuel system cleaner

The condition has improved greatly but has not gone away at this point.

All of the vacuum lines appear to be connected except the "thermostatic vacuum switch" which is on the thermostat has one nipple broken off of it and the vaccum line has been plugged with a screw that leads to the distributor. Could that be causing the problem????

Sorry for the long post, this is driving us crazy!!!!

[Jmark]

Sounds like its running extreemely rich. Does the truck have cats on it? If so, they may be partially plugged and beginning to overheat and smoke out the pipe.

Is it a feedback Qjet? or regular Qjet?

With it idling, look down the carb and see if you see any gas dripping from the nozzles. Could be a bad needle and seat or a bad/sinking float or the float level is too high. May be time to go through the carb and install a new float while you're at it.

[69elcaminoss]

Originally posted by Jmark
Sounds like its running extreemely rich. Does the truck have cats on it? If so, they may be partially plugged and beginning to overheat and smoke out the pipe.

Is it a feedback Qjet? or regular Qjet?

With it idling, look down the carb and see if you see any gas dripping from the nozzles. Could be a bad needle and seat or a bad/sinking float or the float level is too high. May be time to go through the carb and install a new float while you're at it.

Ok, how do I tell if it is a feedback Qjet or a regular???

[Jmark]

If its the original truck carb, its probably not, but thought I'd ask.

the feecback carb will have a throttle position sensor in it, it will have a plug sticking out the front on the drivers side with 3 (?) wires comming out. There will also be a large bump on the top front left with 2 wires on it.

[killerformula]

almost sounds like the bowls are leaking into the carb and the engine is loading up with fuel. COuld be a choke pull-off too.

K

[69elcaminoss]

Originally posted by Jmark
If its the original truck carb, its probably not, but thought I'd ask.

the feecback carb will have a throttle position sensor in it, it will have a plug sticking out the front on the drivers side with 3 (?) wires comming out. There will also be a large bump on the top front left with 2 wires on it.

It doesn't have any of that stuff so I assume it's not a feedback carb.

Killer formula, what would I need to do to fix that problem than?? Have the carb rebuilt or is it something I could do at home.

As a side note: That truck has so many vacccum lines going all over the place. Half the lines were rotten going to the smog stuff from the thermostat so I just ran a vacuum line straight from the distributor to the carb and bi passed all the smog vacuum stuff. That made it idle a little better.

This is getting frustrating.......

[Jmark]

If its the original GM QuadraJet carb and you aren't familar with rebuilding them, i'd suggest finding someone to help. Do NOT buy a remanufactured carb from the stores, they rarely work right and even more rarely have the correct jets and metering rods for the original application.

It might be to your advantage to find a good shop to put the truck on the scope and check it out. They can also check the exhaust emissions to see if it is in fact the carb causing the problems. It will be 40 or so dollars well spent. Been there, done that.

Mark