cam cover blowby flow and crankcase pressure, tiny hole modification - Page 5 - Miata Turbo Forum - Boost cars, acquire cats.

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Old 01-09-2015, 09:17 PM   #81
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Originally Posted by MSMjohn View Post
Scotch-Brite is abrasive. If oil get into the Scotch-Brite & loosens the abrasive grit from the fibers, then drains onto the oil, abrasive grit will get in the oil & wear out all the close tolerance parts causing severe damage. I would remove the Scotch-Brite as soon as possible.
Thanks John. This engine was "Night of the Living Dead" before the Scotch Brite was added, so no harm no foul. I ended up using stainless scrubber material on a different valve cover.

Since this episode I've spoken at the track with a couple of guys who have lots of experience with this issue. More than the scrubber material, the larger hole helps.

The biggest thing you can do is make sure that the stock baffles are sealed so that they work properly. I also re-installed my PCV valve and run either a catch can out the vent or a mini K&N breather. My newly-built engine with these changes has NONE of the issues and none of the blow-by of the old engine...mainly because it's not a tired old engine with crap rings.
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Old 03-17-2017, 03:53 PM   #82
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I have excessive blowby & crankcase pressure on my built Mazdaspeed 1.8L engine. The engine builder used Supertech pistons & rings when I asked for Weisco. I think its the weak piston ring spring tension (half of OEM rings) causing blowby.

Rather than taking my valve cover off & messing with the Mazda engineered system in it. I bought a aluminum oil cap & a 3/8 NPT fitting. I plan on drilling a hole in the oil cap, tapping & installing the 3/8 NPT fitting into it. Then I can run a parallel line into the stock catch can. This should get rid of excess pressures. I may run a second catch can in line on the stock catch can vent hose that goes to the intake. This way the air being vacuumed out of the engine through the catch can system will go through 2 catch cans. Under boost the PCV valve closes & there is no longer manifold vacuum pulling blowby out of the engine. There is a vacuum in the intake under boost that vacuums the engine through the catch can system & helps stop pressure from building up.
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Old 03-17-2017, 05:23 PM   #83
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I would not be totally surprised if you didn't end up with giant oil puddles from your valve cover. turbofan didn't seal his baffles well enough before a track day. And ended up pissing oil everywhere.
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Old 03-17-2017, 08:18 PM   #84
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The oil I'm getting is coming up from the oil pan. Pressure is pushing down on the oil & forcing it up the catch can drain tube. I tested the pressure & it was 1.7psi. I installed a Flyin Miata check valve & it stopped the oil from coming up but the engine still has that extra pressure building up. I want to get rid of that extra pressure. I tested my valve cover vent by having it vent into a clear gallon container & it did not spit out much oil spray. So the valve cover is working fine. My oil cap idea is much better than modifying the valve cover engineering. With the oil cap idea I have more options. I can change the NPT fitting to different sizes to change pressure. I can add check valves. I can add a oil catch between the oil cap & catch can.
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Old 03-18-2017, 01:31 AM   #85
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Oil catch bucket...
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