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-   -   Crankcase vacuum (http://www.clubcobra.com/forums/fe-talk/146888-crankcase-vacuum.html)

cobragene 05-09-2023 08:19 AM
Crankcase vacuum
 
I have a rear main leaking, I can plug or restrict inlet air at my valve cover breather and achieve about 5” of crankcase vacuum with the pcv system, would that help with the leak? Am I doing more harm by not fully venting crankcase? I could regulate the inlet air to get maybe 1-2” of vacuum, has anyone tried this?

Tommy 05-09-2023 08:59 AM
As I understand a PCV system, vapors in the crankcase are sucked out through the PCV valve when engine vacuum is high and fresh air is sucked in to replace it through the breather. At high power settings when vacuum is low, excess crankcase pressure is vented through the breather. So closing off the breather would help build vacuum in the engine during high vacuum conditions (e.g., idle and cruise). But it would hurt during low vacuum conditions as crankcase pressure could escape only through the small PCV valve. So I don't think closing off the breather is a long term solution. . . . As an aside, many race engines run accessory vacuum pumps to lower crankcase pressure as a performance mod. It seems a bit much to avoid fixing a leaky seal.

eschaider 05-09-2023 02:36 PM
Fix the problem correctly. Rear main oil leaks only get worse, not better. Attempting to jury rig a PCV system to draw a vacuum in the crankcase will not work as Tommy already explained. Jury rigging a fix like that will only allow the problem to get worse, and in the bigger picture, is a waste of time. Fix the problem correctly.

twobjshelbys 05-09-2023 02:59 PM
Quote:
Originally Posted by eschaider (Post 1517104)
Fix the problem correctly. Rear main oil leaks only get worse, not better. Attempting to jury rig a PCV system to draw a vacuum in the crankcase will not work as Tommy already explained. Jury rigging a fix like that will only allow the problem to get worse, and in the bigger picture, is a waste of time. Fix the problem correctly.
Gotta admit it's creative though.

eschaider 05-09-2023 06:06 PM
I can't argue with that, Tony. :)

cobragene 05-11-2023 06:42 AM
Quote:
Originally Posted by eschaider (Post 1517104)
Fix the problem correctly. Rear main oil leaks only get worse, not better. Attempting to jury rig a PCV system to draw a vacuum in the crankcase will not work as Tommy already explained. Jury rigging a fix like that will only allow the problem to get worse, and in the bigger picture, is a waste of time. Fix the problem correctly.
You really know how to shut a person and a conversation down don’t you :(

twobjshelbys 05-11-2023 09:14 AM
Quote:
Originally Posted by cobragene (Post 1517148)
You really know how to shut a person and a conversation down don’t you :(
I was originally going to propose that a complete fix could be had by adding enough vacuum to pull air in through the seal. :)

eschaider 05-11-2023 10:33 AM
Quote:
Originally Posted by cobragene (Post 1517148)
You really know how to shut a person and a conversation down don’t you :(
No one is forcing you to do things the right way. This is your car, after all, and by definition, because it is yours, and you pay all the bills, you get to make all the calls. That means whatever you decide is automatically going to be right, for you, until it doesn't work or fails — again.

That does not mean it will be right for everyone else. Some members of the everyone else contingent may actually embrace the same logic that you do and follow your lead. Like you, their car and their call — which makes it right for them also.

For the rest of us who want to embrace the 'generally accepted' right way of fixing a rear main oil seal failure, your approach falls more than a little short of the mark. But, of course, for you, that is not an issue because you have already decided it is not.

The rest of us, well — not so much ...

patrickt 05-11-2023 11:59 AM
Cobragene -- if the leak is not a gusher, just put a discrete little diaper on your bell housing like I described in this thread: http://www.clubcobra.com/forums/fe-t...blueprint.html

Here are two pics:

http://38.134.118.239/diaper001.jpg

http://38.134.118.239/diaperfront001.jpg

cobragene 05-13-2023 09:58 AM
I have read, don’t know how true it is that crankcase pressure can cause a seal leak, so I thought I would just throw that out there, but some people feel that there way is the only way. Patrickt nice job it’s nice to know there are still some hotroders still out there and remember how the sport started with creativity and ingenuity. It’s a great feeling when you can do a workaround and achieve some positive results even if it’s temporary until you get a chance to fix it right, like when I change the tranny. It’s not a gusher so I do have some time. Thanks Patrickt, long live the hotrodders.

cobragene 05-13-2023 10:01 AM
Patrickt why did you tape your engine plate holes? Dirt? I thought they were for cooling.

patrickt 05-13-2023 10:33 AM
Quote:
Originally Posted by cobragene (Post 1517189)
Patrickt why did you tape your engine plate holes? Dirt? I thought they were for cooling.
Yes, just to keep crap out. I don't run the car all that hard so cooling is not an issue. There's a nice RAM Aluminum Flywheel in there so maybe it cools faster than iron. I had Thermax strips on different spots of the drive train, pretending like I'm Morris or something, and I didn't even get the temperatures up to measure on the strips. I kind of new that though because after what I consider to be a hard run I could still reach under the car and not burn my hand on either the transmission, bell housing or differential. And I've burned myself on the side pipes enough to know the smell and feel of a good burn.:cool:


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