BBC Vacumn pump for excessive crankcase pressure
Thread Starter
Race Director
Joined: Apr 2003
Posts: 19,352
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From: Tampa, Florida
BBC Vacumn pump for excessive crankcase pressure
What are your thoughts?
My brothers running a wicked BBC in his Camaro and thinks he needs one because the engine "leaks oil out all of the seals".
I don't know exact specs but I'd imagine the rings aren't the tightest.
My brothers running a wicked BBC in his Camaro and thinks he needs one because the engine "leaks oil out all of the seals".
I don't know exact specs but I'd imagine the rings aren't the tightest.
Le Mans Master
Joined: Oct 2002
Posts: 7,098
Likes: 378
From: Las Vegas - Just stop perpetuating myths please.
He/everyone needs some form of crankcase ventilation.
I could say it all again but u can just as easily type in search for crankcase ventilation on this forum. But if your bro has oil leaking out the seals then it sounds like he has none. Most street cars just use the PCV vlv from vlv cover to the intake. Older car just had a oil fill cap with a steel wool filter inside.
Hope this helps and let me/us know if u have any specific questions after u read up,
cardo0
Hope this helps and let me/us know if u have any specific questions after u read up,
cardo0
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
The crankcase has to have a vent. It can be a simple 'breather' on one of the valve covers; or it can be a PCV valve system which will keep the engine compartment much cleaner. To work properly, the PCV system needs to have the PCV valve in one valve cover and a 'fresh air' pathway from the air cleaner to the other valve cover. This will relieve any built-up pressure in the crankcase.
Pro
Joined: Nov 2007
Posts: 721
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From: hernando fl
a buddy of mine with a 489 in a mud truck is having the same problem,it was leak free until we got it tuned to turn up in the 7000-7500 rpm range,still leak free at the lower rpms,he put a BIG breather on both valve covers and it helped but still is not enough.
we discussed a vac pump but don't think it will pull the volume needed.
we discussed a vac pump but don't think it will pull the volume needed.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
Your engine is the largest 'vacuum pump' available to you. That's why you connect the output of the PCV valve to the base of the carb...the intake SUCKS the crankcase fumes into the fuel charge and burns them. Just use what is already at your disposal....don't add more unnecessary 'junk' under the hood.
Race Director
Joined: Nov 2006
Posts: 19,445
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From: Athens GA
St. Jude Donor '12-'13, '15- '16-'17-'18-'19, '21
I would be looking at the source of all the pressure.
What is CR?
And how old are the rings and what were they speced for?
Has he checked the compression of each cylinder?
I would be looking at those before putting a vacuum pump in which is like a bandaid on a gaping wound.
Covers up the problem but does not solve
imo
Bman
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Pro
Joined: Nov 2007
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From: hernando fl
the engine in question probably has 20-25 hours up to this point,so its like new. i forget what the ring end gaps were set at, but they were all hand fit. the engine is not anywhere close to worn out.if the rpms are kept below 6000 or so it stays dry,that eliminates any assembly errors or worn parts. i,m not sure what its putting out HP wise but it will lift the front wheels on a 7000lb 4x4 truck.
i suspect the excessive crankcase pressure is due to the exhaust being somewhat restricted,however he is not interested in going deaf to stop some oil leaks. we will explore options there next
i don't think a vac pump is even a band aid,just something we discussed
i also understand its not brain surgery to vent a crankcase, but i am also smart enough to know when you build and actually run an engine like this to its full potential there are a few things that crop up that need to be sorted out.
i suspect the excessive crankcase pressure is due to the exhaust being somewhat restricted,however he is not interested in going deaf to stop some oil leaks. we will explore options there next
i don't think a vac pump is even a band aid,just something we discussed
i also understand its not brain surgery to vent a crankcase, but i am also smart enough to know when you build and actually run an engine like this to its full potential there are a few things that crop up that need to be sorted out.
Pro
Joined: Nov 2007
Posts: 721
Likes: 105
From: hernando fl
its not a street car it's a mud truck.........kind of like drag racing in the mud.
a few of the guys he runs with have some sort of a rig plumbed into the exhaust system that creates a venturi ,i need to do more research and see what is involved , trying to keep it cheap and simple.
a few of the guys he runs with have some sort of a rig plumbed into the exhaust system that creates a venturi ,i need to do more research and see what is involved , trying to keep it cheap and simple.
Drifting
Joined: Oct 2005
Posts: 1,528
Likes: 148
From: East London/SW Essex UK
the engine in question probably has 20-25 hours up to this point,so its like new. i forget what the ring end gaps were set at, but they were all hand fit. the engine is not anywhere close to worn out.if the rpms are kept below 6000 or so it stays dry,that eliminates any assembly errors or worn parts. i,m not sure what its putting out HP wise but it will lift the front wheels on a 7000lb 4x4 truck.
i suspect the excessive crankcase pressure is due to the exhaust being somewhat restricted,however he is not interested in going deaf to stop some oil leaks. we will explore options there next
i don't think a vac pump is even a band aid,just something we discussed
i also understand its not brain surgery to vent a crankcase, but i am also smart enough to know when you build and actually run an engine like this to its full potential there are a few things that crop up that need to be sorted out.
i suspect the excessive crankcase pressure is due to the exhaust being somewhat restricted,however he is not interested in going deaf to stop some oil leaks. we will explore options there next
i don't think a vac pump is even a band aid,just something we discussed
i also understand its not brain surgery to vent a crankcase, but i am also smart enough to know when you build and actually run an engine like this to its full potential there are a few things that crop up that need to be sorted out.
Instructor
Joined: Mar 2013
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From: Sunshine Coast Qld