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Discussion Starter · #1 ·
I was reading the other post about the fluctuating oil presssure and decided to post this. My oil pressure is fine. The PVC is OK. After I rev my engine 6K +, the dipstick and breather is pushed up. They aren't out but you can see they have moved up quite a bit. No oil comes out. Anyone else run accross this issue? Is this a problem?
 

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Make sure your breather is breathing. You'll have positive pressure in the crankcase if you're not running a vacuum pump because no piston rings are perfect. If your breather is relatively new and doesn't seem clogged (I guess you could blow through it to check, but if its old, just get a new one, they're cheap) you're probably just getting a little blowby into the case and its pushing at the stick/breather.

I wouldn't leave it running like that for too long, you might start leaking oil if the pressure pops a seal, but after high rev runs, there's only so much pressure you can vent through that small breather hole. If it doesn't seem to do it unless you're hard on it, I wouldn't worry about it - you're creating a huge amount of pressure, and some of that sneaks by the rings enough to build up pressure in the case.

At 6000 RPM, you have 400 cylinder firings a second (4 spark events per revolution, divided by 60 seconds in a minute (4x6000/60). If only 20 PSI makes that into the crank case, thats a pretty small percentage of the combined pressure the pistons are taking (whats getting by the rings.)

How many miles/passes on the engine?
 

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i found it wasnt just pressure. when i started twisting up my old 351w setup, i started pushing up the stick. oil slinging off the crank hits the stick. check out a milodon front sump pan. they put a small ledge in there to help break it up a little.
 

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Discussion Starter · #4 ·
thanks for the feedback. I would be much more concerned if oil was coming out. My breather is new. I have a Miloden deep sump pan. If the retainer on the breather was stronger and the vent holes were larger than it wouldn't move. It probably doesn't take much pressure to move the dipstick up.
 

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Discussion Starter · #6 ·
FE; Thats an interesting thought. I have very tall finned cobra valve covers for rocker clearance. I love these valve covers. My left valve cover doesn't have a tube for another vent cap. It only has a hole for the PVC. There is a round cast area that could be drilled for a tube to be press fit in. I will look into this.
 

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Discussion Starter · #7 ·
I am thinking of eliminating the PCV and running a breather on both air cleaners. Any negative effect on the engine with this setup?
 

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I run breathers on each valve cover.
 

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If you plan on regular oil changes.....3K-5K miles...DO NOT delete the PCV system!! It is a proven oil life extender and protects you engine from diluted and contaminated oil.....


If it is a race car and you change the oil at 500 Mile intervals or sooner it won't hurt a thing to vent both valve covers.....other than you will smell it at WOT!!


My 408W was and still is pushing the stick out a little so I installed a vacuum/pressure gauge and taped it to my windshield. After a few WOT blasts I saw only about 0.2 PSI on the gauge and eliminated CC pressure......I guess it is simply oil flying around in there that is pushing it up??


Cobrajack
 

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Discussion Starter · #10 ·
Cobrajack; I change my oil at low milage intervals. Recently I changed to Royal Purple oil and this problem seemed to decrease. At close to WOT the breather and dipstick still unseats itself. I would like to keep the PCV but it is overpower at higher RPM's. I ordered another cover with a breather provision and will give it a try. I have a 7 qt Miloden pan and windage tray so I don't think the movement is from oil flying around. Where did you hook up the vacuum gauge? Alan
 
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