I have a built 406 that I just put in and finally got running. When it first fires up it blows some smoke out of the driver's side pipe. When I drive it slowly gets worse(but isn't a ton, just enough to notice). When I got it up and running yesterday it was smoking out both pipes then it quit smoking after a while of driving it. I dove it around today and the smoke came back. It seems to be running very rich and I know that could be the carb. It also doesn't have a ton of power but I don't think I have the timing 100%. I am running a pvc valve as well. Only thing I can think of is the head, since its mainly just on one side. Has new head gaskets and intake gaskets (sealed well). The bottom end is new but the heads are not. I bought the motor from a guy on Craigslist and got a really good deal but he didn't have all the specs. What I do know- cowler cam .626 .627 lift(don't know duration ): ), gm crank, roller rockers solid roller lifters, Holly double pump 750 cfm.

Thank you for any help! I've been working on this for over a month and half and the shows are about to start!

 

Blueish/white smoke indicates the heads/s your correct to look in that area could have a cracked 1 but could be really bad valve seals or vavles them selves blackish smoke would indicate being to rich

 

Ok, that is true with black smoke. I've checked my valve lash a few times and was suggested to take the lash the .025 on all. Maybe its the valves themselves. Might jus want to get new heads instead of taking these in and getting tested.

Thank you for the help...