My buddy was behind me while traveling down the road the other day. We were going about 50 mph and I just had to punch it for couple seconds (as in show off my 383).

Talked to him a little later and he says that when I punched it there was some Black smoke and when I let off there was some Blus smoke. ------ What do you read into that?

I'm running a Holley 80508 carb with stock jetting. I do have the quick change secondary spring kit and a very light spring, without bog.

My fuel pressure gauge reads a wobbly 7 to 9 pounds.

 

A puff of black smoke when you stomp on it is fairly normal. If you have any blue smoke, keep a close eye on oil consumption. A puff of blue on decel, could be valve seals leaking a bit.

 

uhh black smokes normal when you stomp on it??! since when?

black smoke indicates your running to rich,blue smoke means your burning oil. running rich wont hurt the car...actually it'll prevent detonation,but burning oil is a :nono:

my350 does neither all i got is white smoke...yunno rollin off the tires...

all seriosness though...it could be either your motor hasnt broke in yet...or your leaking oil past your valve seals...have it looked at.

 

Already moving, then stomping on it kicks the tranny down a gear and the rpms rise much faster than stomping on it from a stand still. You wouldn't want to screw up a good launch by adjusting the carb to prevent a puff of black smoke during a tranny kick-down. Could be some built up carbon blowing out. Puddled up fuel in the intake. If it's not a constant black smoke, your launch is good, plugs aren't showing a rich condition, I wouldn't be worried about the black smoke. The blue on the other hand....

 

For the moment, ignore the black smoke, as everyone else has posted. That's most likely soot/unburned fuel, and won't "hurt" anything.

Blue smoke is bad news. If it's blowing at decel, the high vacuum condition from the closed throttle is likely pulling oil from the heads (valve seals?) into the combustion chamber. If you leave that alone, you will start to get carbon deposits in your combustion chamber.

Look on the bright side, at least you aren't blowing blue smoke at WOT like my vette...

 

First of all, thanks for the responses. Let me just say that this was my first engine build and I am very happy with it. It runs real sweet and very dependable, but does leave me open for some points of constructive criticisim, which I welcome.

It seems to you guys that the Blue is more significant than the Black and you point to Valve Stem Seals.

I should add that she has maybe 5,000 miles on it, new Dart 200/72 Iron Eagle heads.

I should also add that I went with .050" shorter Push Rods so that the wear pattern of the rocker tip would run closer to the center of the valve stem.

Apparently the high vacuum puff leads you to think top end (VSS), rather than piston rings, but what about Valve Guides? Could they be showing signs of wear already?

Thanks gain,

 

It's very unlikely to be rings. I have a motor right now with bad rings and it lays down a cloud at WOT, not when you let off. Under conditions of high vacuum, there's no oil smoke at all.