oil loss through breather

[redneck60164]

need help figuring this out

while driving to ind. on sun my buddys truck started blowing oil out of the breather on the valve cover. we used about 7 quarts of oil to go about 150 miles. we could tell it was starting to get low when the oil pressure would drop from 60 psi. to about 20 psi. we would pull over and put in 1 1/2 to 2 quarts and it would be fine for another 40 to 50 miles. we did figure out on the way back that if we keep the rpms below 2000 it didn't really blow out much oil at all. above that it didn't take long at all. some info on the truck it is a 1980 chevy k10 with 4 inches of lift 35's and 3.73 gears. it has 396 that is bored .30 balanced and blueprinted, hi voulme oil pump.motor has less than 3000 miles since last rebuild. i like to know if anyone has had this problem and how did you fix it THANKS

 

[big83chevy4x4]

sound like you are getting a lot of blowby, doesn't make since with only 3000 miles on a rebuild though.

was the motor broken in properly?

pull the breather or oil fil cap and start the motor, if you get any suction or air comming out, then you have blowby and the motor is preatty much junk. /forums/images/graemlins/frown.gif

 

[Burt4x4]

I had this problem. The oil would hit my heders and SMOKE out the whole freeway. My good buddy Tori came up with a bandade fix. I installed two PCV vavles. Basically bought a Tee and put PCV on each vavle cover. Bam! No more oil pukeing out.
In time the one cylinder that had the blow-by or bad rings started loosing more and more compression.
Good luck

 

[Triaged]

It might also be a problem with the high volume oil pump. Asside from being totally un-needed they pump much more oil to the top end of the motor then is needed. Sometimes it will even pump more oil to the top end then can drain back into the oil pan. He might be filling the valve covers with oil /forums/images/graemlins/doah.gif

I would sugest putting in a new standard volume oil pump.

But before he does anything else the motor needs to have a leak down test done or at least a compression test.

 

[diesel4me]

I had a similar problem on a truck I bought--I found out the reason was the cast aluminum valve covers someone put on had only a PCV valve hole,and the oil filler cap was the stock gm type (solid,no breather hole),so the PCV valve was sucking oil like crazy,the only air getting into the crancase was through the dipstick tube.Replaced the oil fill cap with one that had a breather in it,and no more blowby.
It could be your rings arent seated yet,or maybe they were installed upside down by accident,a 250 six I had that was rebuilt ran perfect for about a month,then it had so much blowby I had to run the "bowtie"breather thing in the air cleaner under the truck with 3 feet of heater hose,to keep the air cleaner from filling up with oil.After I tore it down,I discovered the rings on 4 pistons were upside down!.
Are you sure you have good vaccuum to the PCV valve? If you do,it could mean something serious is going on in the motor,the high volume oil pump answer is worth looking into too.Usually though,blowby means scored cylinders,ring problems,or piston damage--if it was "pinging"it may have put a hole in a piston,a piston skirt may have cracked or collapsed.Try doing a compression test,any cylinders that are low are probably to blame for the blowby.
Hope its something simple--good luck!. /forums/images/graemlins/crazy.gif

 

[rcurrier44]

Another posible option is that you have something in there plugging the holes that allow oil to drain back into the sump. I have seen some bad blow by but you will have a masive power loss and it not wanting to idle if you are pumping oil out that bad.

 

[redneck60164]

i will do a compersion test and leak down test these weekend but i don't there there is a problem with compression it has plenty of power throught the rpm band when there is oil in the thruck there is no strrange noises. we were kinda thinking the oil pump butwanted other opinions becuse we have to pull the motor to change the oil pump because the crossmemeber is within a 1/2 inch of the pan. also it is not burning any oil out of the exhaust, no blue smoke nothing. it also just passed emmisions with no problem. and no cat's.

 

[Smitty]

Had an engine that would build up so much pressure in the crankcase that it would blow the dipstick out. Turned out that the exhaust crossover that went through the intake had a hole in it and the faster you ran the engine the more exhaust it pumped into the engine. Pays to look at everything. I almost missed it because it was under the rivited oil splash plate.

 

[Smitty]

If it just started doing this, I doubt that the problem is the oil pump. I don't know what RPMs you're turning but most of the 396's that I've seen don't normally /forums/images/graemlins/smirk.gif run high enough to pump that much oil to the top end. If you think it is doing this just pull the breather and to see if the valve cover is full to the top. If it is, I'd check the oil return holes in the head like was mentioned earlier.