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General crankcase vent question

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Old 07-26-2012, 01:07 AM
stickbow9 stickbow9 is offline
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General crankcase vent question

Hello all. I am in the process of reading and learning every night from you folks and am feeling more confident daily. So I was reading a few threads about crankcase ventilation and have a question. I have a 77 F250 highboy with 351m with some mods that PO's did (weber/carter carb & intake manifold)and I don't know if it is actually 351 or 400. Anyways, the passenger valve cover has an adaptor in the top with a hose that used to go to the air filter cover. I have an Edelbrock air cleaner and the hose that comes out of this passenger side valve cover has a length of all thread plugging it up. There is also what appears to be a slight leak at the rear main seal area....SO HERE IS THE QUESTION-Without the proper crankcase breather, will there potentially be enough pressure to cause a leak at the rear main seal?
If so, would replacing this plugged up hose with a breather help the situation. Thanks in advance.
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Old 07-26-2012, 01:42 AM
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I have read that yes, it will generate enough pressure to push oil past the seal. youre better off leaving it open than plugged. Mine is open right now, but I'd like to plumb it back to the air filter.
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Old 07-26-2012, 08:29 AM
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Short answer: YES. Proper PCV system is crucial to engine life for many reasons, seal integrity being one of them.

This is not to say that re-routing the PCV system will fix your rear main leak because it probably won't.
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Old 07-26-2012, 11:25 AM
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I would at least remove that piece of all thread, you don't want that hose plugged off.
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Old 07-26-2012, 11:55 AM
stickbow9 stickbow9 is offline
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Thanks for the confirmation. I am going to try the breather first and then possibly change the two piece rear main with it in the truck. Hope it goes well, but the leak only happens after long hot drives that I noticed and is not much at all.
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