455 oil fill tube question

[1965 T5]

Hi - I think I asked this here before, but not sure a reply was ever received that made sense....

When revving over 3000RPM for any period of time, I'm getting oil out of my fill tube. I replaced the tube with a new twist type breather. In this process, I saw that the baffle was in the block at the bottom of tube. I was told that this could be a sign of blow-by, but I don't get how. Seems like I have too much internal pressure????? Internals are stock 10:1 and from a 69 toro. Compression check was awesome with constant pressures @ 145-150psi. Any thoughts?

[first car]

Is your crankcase evacuation system working properly, meaning your pcv valve ?
Most high compression engines need to be evacuated, Summit sells a kit that goes on each valve cover and run's via rubber hose down to a check valve that is installed in your exhaust system on each side, it creates a suction that removes the blow by and sends it out your exhaust pipes.

Race and competition engines use a vacuum pump to remove the gases.

A better way to check engine health is with a leak down test, the tool is not too expensive and will give better results than a compression test.

Hope this helps.

[zodiacblue442]

x2 on it most likely being a faulty pcv valve.

The other valve cover should have a crankcase breather that connects to the air cleaner.

Haven't ever heard of a breather type oil fill tube, unless you mean the cap? :confused: If you do have a breathable cap, you will get some oil residue on the tube after awhile.

[oldstofty]

i capped my oil fill spot and now put the oil in thru the valve covers. I run breathers with hoses to the exhaust. works great 10:1ish maybe a touch more

[1965 T5]

thanks for replies guys! I checked the pcv valve and it works fine. Is it "normal" for the 10:1+ olds motors to blow oil out this tube then? I can't believe it since these were stock equipment, but will accept it. Is it at all a sign of blow-by? I dont think it does.

I have a closed breather w/ outlet for pcv valve in driver side cover and an open breather element in pass side cover.

Any more comments would be great. Thanks!

[70chevrolet]

Sounds like blowby. Compression escaping past the rings forcing pressure into the crankcase. very common on high mileage motors or motors that sat for a long time.. rust builds up in the cylinder walls and when you run it, the rings scraping on the rust wears them down. I once had a 258 jeep engine that had such bad blowby, when I revved the motor oil would squirt out the dipstick tube like a BP oil accident in the gulf of mexico. The motor ran awesome with no ill effects whatsoever. Other than after driving on the highway, the entire engine bay would be soaked with oil. I ended up removing the dipstick, running a piece of fuel line from the dipstick tube up to the top of the valve cover and into the pcv hole, whereby recirculating itself. I drove that sucker for another year at least until I sold it. Just cap off the oil fill tube with one of those expanding rubber freeze plugs. keep an eye on the dipstick tube. if the leakeage is just a small drip and your engine bay isnt detailed I wouldnt worry about it too much. just make sure you check the oil more often than not.