If your breather goes into the airfilter, and assuming you have the standard plastic airbox, check that there is actually a hole in the plastic - the factory didn't fit the breather on to the airbox, but onto the carb itself.

The pop could be pressure building up and sparying crap everywhere.

see my other thread on the rpm valve issue. I think the oil maybe coming from the fuel pump blanking plate. (thanks spank) 

I checked it last summer and could not see oil coming from it even at 4k in the driveway. but I took it apart today and there is not much if any gasket in there. and slight sign of oil getting past what was there. hope that was it won't know until the engine goes back together.

oil from head is pulsed.

took head off.

gasket not blown. no pieces missing. no burn marks. no bent valves. no holes in pistons.

why would an intake valve stop moving at 2700 rpm? then begin moving agin when one lowered the rpm?

Have you checked your oil level? I had a customer car come in with oil leak problems. His base was full of gas the oil level was so high it was running out of the dip stick tube. I'd also wonder about the rate of oil flow to the head. I'd expect the drain holes would allow the oil to return faster than the flow from rockers. Incorrectly installed front cam bearing can cause to much oil to head. You could spin the engine without rocher shaft and see if you have pulsed or constant flow out of head it should be pulsed.

CTR

not a bent push rod took them all out and rolled them on a cookie sheet no bends.

so will have to pull the head to see if I bent a valve. the springs look very good. I don't see any pcs missing or cracks in them.

I had a pop and oil on my engine one day. Turned out to be a small hole blown out of the oil line going to the oil gauge.

If a pushrod is bent you can change it with the head on. But the rockers have to come off (or maybe loosen the suspect one's adjuster and push it sideways off the pushrod).

If taking all the rockers off: do it cold, don't disturb the rest of the head nuts, and retorque ALL the nuts in order after you tighten the back 4 up. You should get lucky and not have a water leak or head gasket issue, this works most times.

If the head is filling up with oil, as Ian says I'd suspect the front cam bush is incorrectly fitted. The rockers should just get a pulse of oil every cam revolution, not a full pressure feed.

Spank and Cup cake were on the right track. I was not able to find this last summer so I just quit driving the mini. well it is spring and I have the need to smell like gas and exhaust

a buddy was over and help me get the mini out of the corner of the garage. fired it up and he thought there was a tiny little miss at about 2k. took the filler cap off (as cupcake suggested) looking I just happened to notice that at anything over 2700 one of the valves on #2 piston stopped going up and down. just stayed in the middle. slow the revs down and it worked again. bent push rod? 

I haven't taken the valve cover off to look any further. Nor have I taken a real close look at the valve springs.

If it is just a bent push rod can I change that without taking the head off? should I take the head off anyway?

 

Check breathers as 1963S advises. If using compressed air to do the second part, make sure the oil filler cap is off so you don't blow gaskets.

The breather that 'goes into a can': is the can vented too or is it sealed with the hose connected to it? Check to see if the can is full of oil.

On my car, both the front timing chain cover and the clutch cover vent hoses are tee'd and connected to the air cleaner. Better I think to route all by-pass fumes to where they can be ingested and burnt.

Check your mechanical fuel pump hole/area. I JUST worked on something that didn't have a good seal at the pump mount (blanking plate with wrong gasket) and it would only spew oil at high rpms or while going uphill. LOTS of smoke from it burning off the headers.

I advise you (if you haven't already) to closely inspect your valve springs to see if one broke. If it's just a coil or two, you could still get good compression readings under crankover, but at high rpms you could get poor closing and weird presurization... just a thought.

I would also suggest a leak down test....much more informative than a compression test..... The pop is a weird one tho....

WeirdEh... I think you got it in one....

Something strange has happened for sure - there really isn't anyway for oil to escape from the top of the motor - except for holes in the valve cover.... bottom gasket, oil filler cap or the seals around the bolts holding it on.  And the only thing that will push oil out is crank case pressure. The compression test would suggest that you don't have a ring problem hence the cc pressure shouldn't be an issue.

I don't think cupcake meant you to take the rocker cover off; just the black/red/chrome/whatever cap that sits on top.  With this removed a CC pressure issue will be obvious - even at idle.  Some oil filler caps are ventilated and if the other breathers are blocked then cc pressure will find its way out here.

Check the breathers by just blowing in the open end (choose the end attached to the engine).  That way, if the breathers are full of mayo, you will blow it out (stick some newspapers under the other end to collect the gunk (if any)... you really shouldn't notice any resistance.  If the pipes are clear then re-attach pipes and blow in the other end to check that the fittings on the engine (where the breathers attach) are not blocked.

Oil is pumped to the top of the engine to lubricate the rockers but the volume is restricted by the front cam bearing.  If someting nasty has happened here the rocker cover could be flooding.  If the cap off test goes OK for fumes,  rev the engine (maybe hold it steady at, say, 3K for a few minutes to see if the cover starts to fill up with oil??????????????. 

Good luck, Ian

Cheleker - I mean it goes into the air cleaner.

Cup cake - without the valve cover the oil runs down the back of the block pretty quick. it dosen't seem to be flying around just that the oil is not running back down fast enough to not overflow.

Spitz - dipstick still in place no oil around it. (on engine)

Dan what is the best way to check for breathing? just feel for air coming out without the hose on? will check that tomorrow.

Weird, not sure what you mean by the clutch vent going into the breather.

Check the dip stick also perhaps....doesn't hurt to check.  Perhaps the "pop" is the stick hitting the hood..... 

If theres lot's of pressure...the oil will indeed find it's way up the dip tube.

Pressures are good all within 10%. What happens at idle when you take the valve cover cap off?

Check that your crankcase vents are really breathing. Hoses could be blocked, resulting in over-pressure of crankcase at higher rpms.

Not sure if it means anything but the compression test shows 140 in #1 145 in #2 145 in #3 and 150 in #4. and it starts and idles really well.

yep still happens. 3500/4000 on the highway for about 2 mins will cause it to put oil on the header. it is then all over the top. front of carb. and all down the back of the block. of course this area is the hardest to clean after each test. can not seem to get it to blow oil while parked.

Cornering at high speed and rpm will create any number of bizaar breathing problems. Is it still happening under normal driving?