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Old 02-26-2012, 03:14 PM   #1
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Default Crank evac inquiry

Currently my engine burns a lot of oil, as I'm sure my rings are wearing and I'm thinking as I enter boost, my crank case also gets slightly boosted due to blow by.
Everybody who has followed Faeflora's build thread has seen his -12 braided line coming off his valve cover which goes to a check valve on his downpipe. The whole reason for this is to produce vacuum in the crankcase, thus helping the rings seal, etc.
Since I currently don't have time to pull my engine apart, and want to add that similar setup in the future anyway...would I hurt if I added a single -12 line with check valve setup now?
Would it improve the way my car runs and cause less oil consumption?
I just feel it's easier to pull my valve cover and weld a fitting onto it, drill my DP and weld a slash cut in there, than it is to pull my whole engine and rip it apart. The engine build will happen someday, I have a spare '99 head I am getting redone, but for right now, I just have to drive my car the way it is...winter '12-'13 build coming.
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Old 02-26-2012, 05:57 PM   #2
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Nobody has theorys or suggestions?
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Old 02-26-2012, 06:01 PM   #3
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have you done leakdown?
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Old 02-26-2012, 07:40 PM   #4
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have you done leakdown?
Negative.
I only did a compression test like 2 years ago, and I can't remember what the numbers were, but they were consistent.
I can say this, my engine has 158,000 miles on it, and 40,000 of that was boosted. It smokes. Lets say I go down a big hill and it pulls a lot of vacuum. When I touch the gas pedal, it'll look like a James Bond smoke screen behind my car. Driving down the street? No smoke.
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Old 02-26-2012, 08:04 PM   #5
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Negative.
I only did a compression test like 2 years ago, and I can't remember what the numbers were, but they were consistent.
I can say this, my engine has 158,000 miles on it, and 40,000 of that was boosted. It smokes. Lets say I go down a big hill and it pulls a lot of vacuum. When I touch the gas pedal, it'll look like a James Bond smoke screen behind my car. Driving down the street? No smoke.
Solid possibility you have bad intake valve seals. Lots of blowby would lead to smoke while you were on the throttle.
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Old 02-26-2012, 08:09 PM   #6
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Jeff, that's the wierdest avatar I've ever seen! It haunts me.
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Old 02-26-2012, 08:20 PM   #7
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Solid possibility you have bad intake valve seals. Lots of blowby would lead to smoke while you were on the throttle.
So what you're saying is, my whole oil consumption issue could most likely be in my cylinder head? Meaning, if I get my spare head redone, I could throw that on and possibly not have any issues?
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Old 02-26-2012, 08:25 PM   #8
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Jeff, that's the wierdest avatar I've ever seen! It haunts me.


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So what you're saying is, my whole oil consumption issue could most likely be in my cylinder head? Meaning, if I get my spare head redone, I could throw that on and possibly not have any issues?
Possibly. Easy button way to check is to pull your intake manifold and have a look at the valve stems. If there is oil all over them you have your answer. A leakdown test wouldn't hurt either.
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Old 02-26-2012, 08:36 PM   #9
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I think I still am going to eliminate my PCV and breather, and run that system anyway. Looks like a leakdown is in order. If I can get away with just a head swap, I'll be stoked!
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Old 02-27-2012, 02:14 PM   #10
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Dude keep stock baffling. Drill out hole between them. Or make your own baffle.
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Old 02-28-2012, 09:44 AM   #11
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Dude keep stock baffling. Drill out hole between them. Or make your own baffle.
You mean the stock baffling that's inside the valve cover? I was just gonna grind the breather nipple off and weld a -12 fitting where it was...isn't that what you did?
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Old 02-28-2012, 10:19 AM   #12
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You mean the stock baffling that's inside the valve cover? I was just gonna grind the breather nipple off and weld a -12 fitting where it was...isn't that what you did?
No, I don't use the passenger baffle because the driver's baffle is longer.

See this thread regarding the connecting hole.

https://www.miataturbo.net/showthrea...ight=tiny+hole

I enlarged that as much as possible.

Note that the only problem with the slashcut in my experience is that sometimes, under some driving conditions, oil goes into the tailpipe. Lots of it. When that happens, unlike a VTA catch can setup, your exhaust will smoke A LOT.

If I did this over I would put a can in the line. Of course this will add about $120 with the can and fittings. The fittings are $35 apiece :| You can get a custom aluminum can from

http://www.petersonfluidsys.com/tank_spec.html

for like $45 and that includes bungs and petcock. I have one sitting in my garage. Just call em and tell em exactly what you want, and they will send you a technical drawing for your approval. Amazing source for... cans.
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Old 02-28-2012, 10:25 AM   #13
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Nice, all the Moroso units I found come with 2 check valves (for V8's)...do you have a link for just the single?
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Old 02-28-2012, 10:44 AM   #14
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Old 02-28-2012, 10:52 AM   #15
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+1 on compression test
also if you do the test and discover 1 or 2 cylinders are a little lower then the other 2, adding oil and testing again can help to point you in the right direction as to if the compression is leaking via the valve stem seals or rings -
if adding a little oil causes the compression to go up it's usually an indication that it's your rings
if adding a little oil results in no change it's more likely the valves

although it's a different car principals are still the same here's the fsm's detailed description on my old car -



it's probably more important to find the real source of your issue before you just guess at parts to install to fix the issue
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Crank evac inquiry-ct1.jpg   Crank evac inquiry-ct2.jpg  
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Old 02-28-2012, 11:07 AM   #16
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I have a compression tester, so this weekend I'll get new numbers. I also will do a leak down test and post all results. Like I said, if I could get away with doing a head swap, that would be so awesome.
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Old 02-28-2012, 11:10 AM   #17
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Thanks for the link Min..I guess I'll order just 1 slash cut and 1 replacement check valve. Since the valve is steel, I bet I could weld a -12 fitting on it so I don't have to be sloppy and use a hose clamp.
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