Guy you know how if you have no PCV system and there will be smoke / steam coming from your oil filler neck when engine is warm? Well its coming from the corner of my oil valley pan right by the oil filler neck too. What gives? Anyone else get this happening and should I order a new aluminium pan? This one is the original but the engine has be completely professionally rebuilt. I have been tunning the hell out of two different carbs trying to get a small exhaust backfire out and I think this may be the culprit. Thoughts?

If it's coming from the junction of the tube and the pan, the crimp securing the two together has become loose. If the pan corner is the problem, the pan is distorted, what about the breather cap, nothing from there?
 Plugged breather cap?

no it does come from the breather cap just a tad which I am told is normal. I have a PCV system where it comes from the valve cover to the carb. It breathed too good and made a major vacuum leak so i have a hose clamp crimping the hose to where the vacuum is very little. Is I loosen the hose clamp no smoke comes from either. if its tightened down then smoke comes from both the oil filler cap and the corner of the valley pan. at least it seems like the corner of the valley pan. could be the intake? i am going to check around with some carb cleaner tonight. I can use that method with a hot engine correct? i just have to be careful and use little squirts? 

The more you choke off the vacuum for the PCV the more crankcase pressure you are creating..

You can experiment with different PCV Valves or try a restrictor inside the hose to change the amount of air that passes. I ended up using One for  1980 Fairmont/ Zephyr 4 Cylinder. The One for a 302 which I tried first was causing a vacuum leak passing too much Air. Its not unusual to find the Valley Pan is distorted from Years of over tightening the Bolts which causes the Corner to lift. Specs call for about 3 lbs or similar Torque for the Bolts. I drilled and tapped the Block to use a few Machine Screws around the perimeter of the Valley Pan. No Leaks now. Wish I could say the same about the rear Main Seal. 

  

For PCV valve installations on the Y’s, I use the Microgard 2322 PCV valve.  It’s important that the carburetor being used is one that’s designed to use a PCV valve; the metering circuit will accordingly be on the rich side to compensate for a ‘designed’ vacuum leak.
 
Blowby coming from the gasket area of the valley pan simply suggests a poor gasket seal in that area.  With a little bit of driving, there should also be evidence of oil leaking from that area assuming a poor valley pan gasket seal.  Valley pans are known to leak first in the oil fill tube area simply due to the pressure that’s exerted on the tube to remove/install the oil breather cap on that tube which in turn deforms the valley cover.
 
As far as the backfiring goes, it’s unlikely that any kind of poor gasket seal at the valley pan has anything to do with that.  For the backfiring, I’ll suggest looking for a vacuum leak, improperly adjusted valves, valve seating issues, ignition timing incorrect, point gap, spark plugs, spark plug wires, weak voltage to the coil, and/or carburetor problems.  Some of these issues can be isolated using a vacuum gauge hooked to a direct vacuum port directly under the carburetor.  If using a timing light to verify the ignition curve, then the damper must be checked to insure it has not slipped thus giving erroneous timing values.

Lorena, Texas (South of Waco)