Oil Dipstick keeps migrating out of tube.

[amdscooter]

I feel like a bit of a "dipstick" for even posting this question.. but too late now. ;p The oil dipstick on my 390 keeps coming out of the tube. I usually catch up after it is out a few inches. Not a huge issue but it does let oil get sprayed into the engine compartment and it's enough to collect on the frame rail. I can probably fix it with a small tie down or by flaring the tube, but I'm wondering what might be causing it to do this to begin with? If there is a real problem I'd like to address it. I have the crank case properly ventilated  (PVC valve is checked and fine) and don't think it's coming out from excessive vibration as the engine really does not shake any more/less than before and I never had an issue prior. I have a Melling HV oil pump and do keep about 1 quart extra oil in the pan. Any ideas? Should I sweat it or just put a leash the darn stick?

Thanks in advance
-Scoot

[bn69stang]

Is your oil filler cap a ventilated ? clogged ? .. Bud

[rockittsled]

Have you don a compression check lately?  Blowby past the rings has to go somewhere

[amdscooter]

The filler cap is ventilated and does not appear to be clogged. I have not done a compression check in a few months. I'm not getting "blowby" anywhere else that would lead me to believe I'm losing compression and the engine is running great.

[machoneman]

A blow-by meter is best yet even good shops may not have one.

http://www.aa1car.com/library/engine_blowby.htm

Next would be doing the old compression test; better would be to also do a leakdown test. 

Last.....block or tape off (duct tape, what else?) all crankcase vented openings, disconnect the PCV, etc. Hook up your combo vacuum gauge/pressure gauge with rubber tubing and some small screw clamps to the dipstick tube. Fire it up and let it idle.  More than approx. 1.5"-2.0" of pressure indicates more blow-by than one should have. JMO

[cammerfe]

It has been fairly common on 'track' motors to hold the dip-stick in with something like a section of screen-door spring.

KS

[Joe-JDC]

Another possibility is that the dipstick is so close to the crankshaft that it is hitting ever so slightly, and being pushed up out of the tube until it clears the crank.  Check the end of the dipstick and see if there is a slight burr, or scratch that would indicate contact.  The dipsticks can become bent just enough to let them hit, and you might not see it, or hear it.  I have one that I can only put in one direction, or it will hit the crank.  Joe-JDC

[amdscooter]

^^^ Will do, thanks for all the suggestions.

[Qikbbstang]

That brings back the memories. Had an 80s 302 F150 that looked great but likely went around the odometer a few times. Nailing it would lift the dipstick about an inch and shower the exhaust manifold with oil making a stinky smoking mess -  why it never burst into flames scares me when I think back. Amazing thing it passed state emissions testing!