White smoke out of valve cover vent

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Old 01-02-20, 02:10 PM
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White smoke out of valve cover vent

I'm helping my nephew troubleshoot an issue with the 1960-something GMC truck he's been restoring. The engine is running, but there is white smoke (maybe steam) coming from the vent cap on the passenger's side valve cover. He does not have a PCV system connected at the moment. Just a crankcase breather filter on the driver's side and vented cap on the passenger's side. There is no smoke coming from the driver's side, and no smoke from the exhaust. Motor idles fine and sounds good, but still some driveability issues that need to be sorted, which are believed to be carburetor related (not positive at this point). Should he go ahead and install a PCV system? How exactly is that done? It is my understanding that a check valve would be installed on one valve cover with hose leading to the base of the carb (Holley classic) and a hose would be connected from the other valve cover to upstream of the intake. Is this correct? Quite frankly, I'm confused as to why smoke would be coming out of one valve cover and not the other. If there is blowby and positive pressure in the crankcase, shouldn't smoke be coming from both covers?
 
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Old 01-02-20, 06:41 PM
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(maybe steam)

You have head gasket issue. It's blown on one V side, that's why.
 
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Old 01-02-20, 09:19 PM
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you would have to install a manifold from a later model engine with a pvc port in it. I I would not do it. Chevy engines of that year had a rear drain hole in head that tended to become clogged and would smoke. Will eventually # 7 plug will foul out. Oil pools in valve cover.
 
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Old 01-03-20, 09:46 AM
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You have head gasket issue. It's blown on one V side, that's why.
If it were a leaking head gasket, wouldn't smoke/steam also be coming out of the exhaust (there isn't)? You don't think blowby from worn and/or sticking rings is more likely?

Just realized I posted in the car forum when this is technically a truck, but we're talking about the engine only, so probably okay.
 
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Old 01-03-20, 11:00 AM
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If it were a leaking head gasket, wouldn't smoke/steam also be coming out of the exhaust
It depends on where it's leaking - it will either go out the exhaust or into the coolant. How does the coolant and oil look?
 
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Old 01-04-20, 08:04 AM
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MM, you have fluid getting inside the valve cover. Whatever the source might be. It can be anything from old/new condensation (VW is said to be real bad about that, down to oil frappe), coolant particles getting in, cracks somewhere allowing coolant to go in.
 
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Old 01-04-20, 03:41 PM
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typically you would have a pcv valve in one valve cover and a breather style filter in the other factory did often ran a hose to the air cleaner but is not required, really not going to solve your issue though sounds like excessive blowby or head gasket or something is wrong need to do some checks on it like cylinder leak down test.
 
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Old 01-09-20, 11:11 AM
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I'll bring my leakdown kit with me next time I go over there. I don't believe that is something he ever did (he was anxious to get the thing running, understandably).
 
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Old 01-09-20, 09:10 PM
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You might check the cooling system for air after warmup.
 
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