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Discussion Starter #1
I need some opinions before I do a teardown on this engine. 406 small block with about 2K miles. Problem started about 1500 miles after engine was built.

I developed oil smoke (blue) when decellerating from above 4K RPM. This is not just a little smoke, it is a significant amount. It will smoke until the car idles down. There is no smoke noticeable at idle or on start up.

At a lower RMP cruise <3K or so there is very little smoke on decelleration.

I pulled the manifold twice thinking it was a seal problem. I also changed out the heads both iron and aluminum and have same issue. Both sets of heads were fresh.

The smoke is from the passenger side, same amount of smoke after each of the part replacements.

What I think I know is that it's not an intake leak or a problem with valve guides or the heads.

Leakdown and compression test show OK.

What about an oil seal ring?
Would a block crack only exhibit this under high vacuum?

There is no fluid mixing in oil or coolant.

Otherwise the engine runs real strong.
 

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Do you have a pcv setup and is everything baffled? Is this hard decel or moderate/coast down? Over 4K there'll be more oil on top, I would think, and my thinking is if it's getting sucked into the intake. I take it you have true duals with no crossover and are seeing the smoke from the pass tailpipe?
 

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Discussion Starter #3
Thanks Rick, Yes I have a baffled PVC and the dual exhaust has a crossover.
I read your post and it got me thinking about a post I read a while back on the position of the PVC (driver or pass side) Mine is on the passenger side. I am going to replace the PVC and swap sides and see what happens. I just pulled the PVC hose it is not what I would call "wet" but it does have some oil in it. Hmmmmm
 

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When my pcv was sucking and burning oil it was visible under acceleration... When I had a valve guide problem is smoked under deceleration...
 

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Smoking on deacceleration is usually a valve guide problem or an intake gasket issue that sucks oil from the underside when manifold vacuum is high. But I hope the PCV is the issue since that is an easy fix. Perhaps you could temporarily plug the end of the PCV valve and take it for a quick spin to see if the smoking goes away.
 

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If your pcv is on the pass side that could be it.
 

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Discussion Starter #8
Seems I might be dialing this problem in. I swapped sides for the PCV and drove it today. It is much better. Still some smoke after high RPM on decelleration but <1/4 of what it was.
Since the guys at the parts store can't tell me, there are a lot of different part number PCV's that are identical on the outside. Anyone have any experience with any certain part number.
And...what about plumbing, I have the power brake booster directly into a manifold port and the PCV into the rear carb port. Is there any difference in vacuum between these (lost my vac gauge?)
 

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The rear of the carb is good. There are different pcv's. A post a while ago stated some part numbers, maybe a search will find it. I have them written down at work and will check monday. What application part # are you using now? Great progress!
 
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