I have a 68 Camaro with a 350 motor, about 300 horse and have recently started getting blow by at the oil filler cap. Once the cap is full it blows thru the cap on the valve cover and back on the firewall and inner fender wells. If I put a paper towel around the bottom of the filler cap to stop and catch the oil the pressure then pushes the oil up the distributer shaft and out the bleed hole in the bottom of the distributer. The motor makes about 20lbs pressure ideling and about 55lbs at 2300 rpms. It has a standard oil pump and I've even put a set of tall valave covers on it to try and cut down on the amount of oil coming out. I can put a new oil filler cap on and within 500 miles It's blowing it out again. Anyone else ahd this problem or have any suggestions? Thank you.

I have not heard that type of problem before without the oil pressure being off the scale. Hopefully one of our members that also a n automotive mechanic will have some suggestions. Are your sparplugs also fouling up due to the oil?

No, spark plugs are fine and the car runs fine, no skipping or missing. I look forward hearing from your friend that may be able to shed some light on this. Thanks for your help though.

Found some good info here. http://forums.superchevy.com/70/7677772/tech-talk/oil-blow-by-at-filler-cap-and-distributor/index.html

I actually wondered if maybe a oil return has gummed up and letting pressure build. Has anything else changed on the car? recent work? Does the car get driven much, and does the blow by get better or worse as it warms up.

No recent work on the motor and it does get worse at higher rpm's. Car is mostly driven on weekends to car shows and such but I do like to wind it up pretty tight thru the gears. Other then pulling the heads, or at least the valve covers, and trying to clean the oil gallaries, do you think stuff like gummout would help any in cleaning them out? Anything else you might suggest that might break it lose better? I appreciate your advice, I hadn't thought about some of the gallaries getting clogged up and causing pressure to bild. Thanks for your help.

Seafoam might work too. You put 1/3 the bottle in the tank of about 9 gallons of gas. 1/3 in the oil then change it after driving 10-20 miles. The last bit you put in the intake. You'll let a vacuum line on the intake suck it in.

Car will smoke like a banshee but shoudl clear up within 10 minutes.

also check that link I posted. They mention there that the PVC could be a problem as well.

I will try the sea foam along with any other suggestions anyone may have. I have installed a new PCV valve and the more I think about it the more I am leaning toward the oil gallaries having some obstruction that isn't letting the oil drain back into the block and oil pan. Sometimes the simplest things are the easiest overlooked. I'll let you guys know how it goes. Still open to other suggestions and recommendations. Thanks again.

Are your valve covers baffled?

Want to say thanks to Zonestar and Beeme for your help. I think I've got a handle on the blow by at the filler cap. I did take your advice, Beeme, and tried the Seafoam. I ran it thru the crank case and after a driving it a bit the blow by has all but stopped!! I am changing the oil and filter and going to run some more of the Seafoam thru it and see if that takes care of the problem. Thanks again guys, I appreciate your help.

Thanks great news! What weight oil are you running, and conventional or synthetic? A thinner oil or synthetic might blow by no matter what. Synthetic is slipper for older engines to control.