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Discussion Starter #1
This is an update to the post I did last week about blowing blue smoke when I gun it and when running hot. I thought it might have been too much oil in the crankcase, but it turns out I was actually running a little low. Somebody somewhere posted about getting oil being sucked in to the carb thru the PCV hose on acceleration. I checked my PCV hose and sure enough, there was oil getting into the carb. I disconnected the PCV and set it up as a draft tube?! No more blue smoke. I don't get any coming out of the PCV hose anymore either. Is it possible the vacuum is so strong that it is sucking the oil into the carb? I have no problem with leaving it the way it is, just curious as I would think other people would have had the same problem before and why now, all of a sudden? Things that make you go hmmm....
 

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It's good to hear you've found a temporary solution.

The bad news is that it is only temporary, because excessive oil vapors coming through the PCV are almost always due to blowby caused by worn piston rings.

You should check the compression to confirm this diagnosis.
 

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Discussion Starter #3
I was afraid it might be the rings. I'll have to get a compression gauge to check. I needed to get one anyway.
 

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Hmmm ... I've had the same problem. I installed a new PCV valve, no help. I hadn't considered that even a new valve can let blow-by into the carb. I'm going to try disconnecting the PCV to see if the smoke goes away. Couple questions:

Will it harm the engine to run with the PCV disconnected?

Should I plug the PCV side and the intake side? If I leave the PCV side open, won't I get fumes in the car?

Thanks
 

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Discussion Starter #5
I don't think it will harm the engine as they didn't always have PCV valves. They just used to have a draft tube that basically went downwards to the bottom of the engine bay. I would plug the intake side otherwise you would have a vacuum leak and it would run pretty rough or maybe not all. As for the fumes, I was thinking of running the hose (without PCV valve) to the air cleaner. I've got one of the 14" ones with a punch out hole that you can connect it to. My 70 mustang used to have a hookup like this and it worked fine. Are your rings worn by chance. I haven't checked my yet but, could it be maybe a worn seal on the intake guide?
 

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Thanks, I think I'll try just running a tube down from the PCV port on the valve cover and see if I smell fumes. I'll also plug the carb hole.

Seems like running the PCV tube to the air cleaner will have the same affect as to the carb. You'll still be pulling that oily air through the engine. Am I wrong about this?

In my case, my engine only has about 30K miles on it, so I'm doubting it's rings. I have a nasty feeling it may be valve seals. I exchanged for a cheap rebuilt longblock, maybe there's a reason it was so cheap!
 

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Discussion Starter #7
When I have my PCV vavle hooked up to the base of the carb, I get actual oil coming thru the hose(it was all soaked with oil on the inside of the hose). After I disconnected the hose, I don't get any oil, just fumes. I was thinking that maybe the vacuum is helping to suck to oil out into the tube. The vacuum should be alot less before the carb I would think, and hopefully it will just have fumes and none of the oil coming into the air cleaner. Doesn't hurt to try I guess. Let me know what you find out, if it's a bad seal or not.
 
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Do you have stock or aftermarket valve covers? Some of the a/m types have no baffles so it's a
straight shot splash for the oil into the pcv to be pulled into the carb.
 

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On the 331 project we just finished, we had the same problem, due to the fact that I have valve covers with no baffles. We just put breather caps in both valve covers and omitted the pcv valve. It only drips a drop of oil every now and then. Another tip my machinist gave me is to install a sock over the breather cap to absorb any oil that may find its way out. However, you cannot do that with a pcv.

Dave
 

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Discussion Starter #10
I do have aftermarket valve covers. I'll have to check this weekend to see if there are any baffles or not. Thanks for all the replies.
 
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