I have a 5.9 mag in my dakota, upon high rpm deceleration it blows a good bit of oil smoke from the exhaust. It doesn't do it any other time. Its a pretty fresh rebuild, new rings, intake with a carb swap and edelbrock heads. What causes this

 

Maybe valve stem seals. Did you change those?

 

x2 on valve stem seals or the kegger bottom pan. Could also be oil rings, but that would be a more constant plume. Closing the throttle at high RPM makes a heavy vacuum in the intake manifold, making oil get sucked through the valve stem seals into the intake runner, or through the intake manifold's bottom pan gasket.

 

Don't forget the PCV system as well. If there is an aftermarket valve in there, dump it, get a real mopar unit. They were less than 10 bucks last time I bought one.

 

Something to consider, when you let off the throttle and engine decelerating .... this is when the vacuum in your engine will be the strongest.

While I worked on chasing down the issue for some time ..... extended periods of idle time in blocked traffic it would suck oil out of the engine and run it through the throttle body creating a lot of blue smoke and a need to add oil often.

While my issue is different then yours, the important thing to remember is the engine has the highest vacuum at a idle. ..... check out your engine and figure out why it might be sucking oil out of the engine and through the burn cycle.

I do not know the answer, the pvc system and anything near it I would be looking at.

 

I have an aftermarket intake manifold, as i am running a carb. So the plenum couldn't be leaking. Also my pcv from the valve cover is vented to the atmosphere. I didn't replace the valve stem seals because i bought the heads brand new pre assembled, so i figured they were good

 

How many miles on the motor? Could just be the rings haven't fully seated yet.

 

Id say around 5000 miles, maybe closer to 10. Also, on startup it has what sounds like lifter tick for a few seconds and goes away. The tick seems to go away slower on hot starts.

 

What oil are you running?

 

10w30