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Smoking out of the breather cap
https://www.slantsix.org/forum/viewtopic.php?t=26653		 Page 1 of 1
Author:  SpaceFrank [ Sat Jan 12, 2008 7:24 am ]
Post subject:  Smoking out of the breather cap
I just finished a bunch of work on my 64 Dart 225, including mounting a Weber 32/36 DGEV to a stock 2-bbl Aluminum Intake (an interesting process which I will detail later...), and after test-driving it, I noticed a slightly rough idle when warm, accompanied by an excess of white smoke coming out of my oil breather cap.

The first thing I did was replace my PCV valve. I also did a compression test, and all 6 cylinders showed 115-125 psi. I'm assuming that's alright. After driving it some more, the smoke did not go away.

This engine was rebuilt about 4 years ago. The compression test seems to rule out bad valves or rings (I hope you gentlemen can verify that for me), so I'm thinking I might have worn out valve seals. The smoke looks worse when the engine is hot, maybe because the seals get warm and loosen up? I also normally get a little smoke out of my tailpipe at startup after it sits for a while.

Also, I pulled the crankcase vent hose off the carburetor and it doesn't seem to be pulling any vacuum, at least not enough to feel at idle. I had to build my own adaptor plate to make the Weber fit, so it's possible that I could be blocking off that vacuum port. If necessary, can I run the PCV hose to one of the ports on my intake manifold?

Is my analysis correct? If so, how does one go about replacing valve seals? I hope you can do it without removing the cylinder head. How long could the car be reasonably driven before doing this repair? (I'm crunched for time and need to make a 6-hour drive to Houston.)

Thanks in advance.
Author:  SlantSixDan [ Sat Jan 12, 2008 7:54 am ]
Post subject: 
Yep, you've nailed it: No vacuum to the PCV valve. There's no PCV port on the 2bbl intake's carb mounting plate as there is on the 1bbl intake carb's mounting plate; the PCV is routed completely through the (stock) 2bbl carb throttle body. Don't route the PCV to the vacuum takeoff on the #6 intake runner; you'll make cylinder 6 run lean. The PCV needs to be routed to the central plenum area of the intake. Since you're running a late-model intake manifold, the easiest way to do this will be to drill and tap the EGR valve blockoff plate and install a hose nipple. Make sure to drill the blockoff plate in the correct location to route the PCV to the intake, not to the exhaust! :shock:
Author:  SpaceFrank [ Sat Jan 12, 2008 8:15 am ]
Post subject: 
Thanks for the reply. Could you tell me where the block off plate is located? I see three threaded holes and a brass plug that goes into the exhaust.
Author:  Aggressive Ted [ Sat Jan 12, 2008 9:31 am ]
Post subject: 
If you pull the EGR valve off, undue the two nuts and pull it off, the exhaust is the left hole, the right hole goes to the plenum. That is what Dan is referring to, right under the carb.
Author:  SpaceFrank [ Sat Jan 12, 2008 10:51 am ]
Post subject: 
I don't have an EGR valve that I know of. I see one hole that has a plug in it, when looking at the manifold from the driver's side. In any case, I found another vacuum port to use on the carb itself. It turns out I was plugging my PCV hose into a port designed for the breather cap to use. It just led into the air cleaner. :oops:

I took apart my homemade adapter plate and drilled a few holes to make sure the vacuum ports on the bottom of the carb get free flow into the central throttle passage. I can now feel suction when I pull the hose off the PCV valve.

Unfortunately, there is still a small amount of smoke coming from the oil inlet while idling. It's only noticeable when the breather cap is removed. When I increase the throttle, more smoke blows out immediately, then it settles down to the same amount as before. Do I still have a problem here? My PCV hose leads to a 1/4" vacuum nipple, is that large enough? Even if I pull more vacuum by tapping into the plenum, should I have that much blow-by in the first place?
Author:  SpaceFrank [ Tue Jan 15, 2008 8:24 am ]
Post subject: 
Thread bump. Should I be worried about this smoke? Is there a way to measure the vacuum from the line going to my carb, and if so, how much should I need for the PCV valve?
Author:  SlantSixDan [ Tue Jan 15, 2008 9:42 am ]
Post subject: 
The factory setup is an 11/32" ID rubber hose leading to an appropriately-sized nipple, which connects to a passageway drilled in the carb's throttle body, which follows one path or another depending on carb model and build date, and dumps out under the throttle plate(s).

I can't quite picture the vacuum path your PCV airflow takes starting at the carb end of the hose.

It sounds as if somebody used a method other than a blockoff plate to block off the EGR provisions of your 2bbl intake. A photo would help.

The smoke indicates you have some blowby (combustion gas escaping past the rings). Some blowby is normal/acceptable. It's difficult to say so far whether your engine has excessive blowby. A leakdown test (not a compression check) would say for sure. But I think once the PCV system is sorted out and put together correctly, probably the smoke volume will go down.

How about some photos and/or detailed, step-by-step description of the routing of your entire crankcase ventilation system? And, what're you using for a PCV valve?
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