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We are having an issue of blowing oil out the valve cover breathers. We even ran a hose off the valve cover to a fill can with a breather on it and it's filling the can with oil and blowing oil out of that breather as well. We are having to add 2-3 quarts of oil throughout the night not to mention the mess. Any suggestions on how to fix this?
sounds like bad rings or scratched cylinders
Time for a rebuild
Was hoping that wasn't the issue, only 300 laps since rebuild
Run a leak down test and see for sure
Check to see if the slits in the valve cover were the filer goes on have been opened up to let oil go into motor faster when oil is changed.
If not sounds like a lot of excessive blow by, crankcase pressure.
I race at one track that I have that problem, but only at the one track. Long straights, tight turns.
Too much oil staying on top? Check your drain backs on the head... are your valve cover breathers baffled?
Wouldn't his spark plugs be coated with oil if that much was getting by the rings? I cant imagine the motor even running with that much blow-by!
I'm a crew for 2imp. this motor has had this issue since it was new. It has the orig. spark plugs. we are thinking about trying the crankcase evac kit from day mtrsprts, that hooks to the headers. leakdown test sounds like a good idea before we go any further. thanks everyone.
total seal rings?
I have one doing the same once it gets to speed. Compression is good, leak down is good, plugs are good. Was going to try different valve covers Sat. night but it rained out.
Let me add - motor has 62 laps around Devils Bowl, 20w50 Valvoline, alk for fuel. Total Seal conventional rings.
Many times (if the engine don't have excessive blow by thus excessive crankcase pressure) it's the breather system:
Too high a velocity of air coming out of breather area, this doesn't allow the oil droplets to drop out of the air before making it all the way out of the breather system. Think of it this way: You have air/oil droplet mixture in the crankcase volume, if the air is going 100MPH out the breather it won't un-suspend the oil from the air and take the oil out with the air. Now slow the air down to 10MPH and the oil will drop out of the air before it makes it out of the breather system.
People stick stuff in the breathers to try and separate the oil but are blocking or restricting the air movement and thus increasing the velocity of the air compounding the problem. I have seen too small a hole in the valve cover under the breather stand cause this and just opening the hole up to reduce the velocity can/does stop this.
Ideally you'd like a large diameter area and something reasonable tall that allows time for the weight of the oil to make it fall out of suspension and not come out with the air as the engine allows the crankcase pressure to escape.
Also make sure if your using an external breather that the line doesn't have a dip in it. Oil can accumulate in the line slowly at the dip and once it blocks the line the air will push the entire volume of oil out cause it's blocked by the puddle of oil in the dip in the line.
odd question but, what side of motor are breathers on?
Coming from both Driver Side breathers or just one? Blow by generally effects both breathers and oil control often just one.
Drivers side rear on the one I am working on. But the front one is not totally dry either.
we do have total seal rings. we had tall alum. valve covers with two 1.5 inch breathers on drivers side, but changed to a set of alum. covers with a -8 an fitting with a hose running to a cannister with a breather on top. this settup seamed to be even worse. makes sense with what billetbdcg says, not enough volume.
We had a set of valve covers that always leaked a little out of the breathers. We finally started putting a folded up blue shop towel in each one. We would change the shop towels every 2-3 races and never had another leak issue.Quote:
Originally Posted by modstar
I use old socks on my breathers works perfect the elastic just slips over the breathers everyone has old mismatched socks cheaper than outerwears.
I would stay away from the crankcase evac as this can pull oil off the top of the valve (bad). more drainback is always better ,especially if you flooding the top w oil. JMO
I vent the intake above the valley.
Drill a hole and weld in a bung or tap for a 1" AN fitting.
Doesn't suck oil off the valves, There's a much slower moving gasses under the intake to reduce aeration, far away from the cam/lifters so no issues there.
You can also pull a vacuum with a pump or the header evacs systems without as much worry of oil coming out with it and it works well on street cars and looks better with closed valve covers. You can add a baffle under the vent bung or even a valley pan if you want too as well. It's also a good place to add oil when needed.