Hello
I have a "68 327 with a 2 barrel Rochester.
In the morning at start up It blows out alot
of wet black carbon on the concrete. I smelled that it was burning very rich (Gas, Exhaust smell)
I turned both the air and the fuel adjustment
screws in 2 and one half turns, tried it again
this morning and it still blew carbon. What is a good way to adjust the carb? I dont know if the
carb will need rebuilding, it has no exterior leaks and the housing has been tightend up to avoid air,fuel leaks. Thanks for any information

Stop!! Don't go anyther further until you get a copy of the '68 Chassis Service Manual or some other info that provide factory settings for your carb and engine.

You can't tune a carb cold, so get the engine to operating temp. One of the two screws you turned controls the throttle butterfly and the other controls the idle fuel mixture. If the idle is set too high, throttle butterfly is open too far you won't be idling on the idle ciruit and turning the idle mixture screw will have little or no effect. Your carb also has a choke and it needs to be adjusted properly. It's function is to richen the air fuel mixture when the engine is cold and it could also cause the problem you're having.

Not to complicate this but it does sort of... Your timing needs to be set properly before tuning the carb. Not enough initial timing can cause you to open the throttle butterfly too far to get the car to idle...

By the book, initial timing should be 4 degs btdc but the book is conservative and you might want to try as much as 8-10 degs btdc. Drive the car and listen for any pinging once you increase the timing. If it does ping, back it off and drive again... Always disconnect vacuum advance and plug when setting or checking timing...

Val,
I have the same set up as you. I get moisture - carbon from the exhaust also. My choke thermostat (coil) broke so the choke is de-activated at the present.

I assume the exhaust junk is due to this. One thing I'll have to figure out is how to adjust the choke once I get the replacement thermstat. Any tips?

By the way, I ordered the service manual 3 days ago. Thanks!

Originally posted by Domano 68:
Val,
I have the same set up as you. I get moisture - carbon from the exhaust also. My choke thermostat (coil) broke so the choke is de-activated at the present.

I assume the exhaust junk is due to this. One thing I'll have to figure out is how to adjust the choke once I get the replacement thermstat. Any tips?

By the way, I ordered the service manual 3 days ago. Thanks! Unless your choke is stuck on it's not causing the problem of rich idle... The choke on that carb I believe is called a divorced choke, a coil that sits in a well at in the manifold at the base of the carb. As the manifold warms up the expands opening the choke butterfly and lowering the fast idle. If the rod that connects the two is removed the choke butterfly should rest in the open position. I don't know what part broke but just remove the rod until you get your replacement...

I am not 100% sure how to tell if the choke is stuck on, or partially stuck on. The plate is almost vertical, 80-90 degrees from horizontal.

I do have the divorced choke and the coil is the broken part. The rod is just hanging there for now, but I'll try the removal to see if that helps. I also am experiencing poor gas mileage so maybe the choke is stuck partially.