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Possibly the rings in the new engine are not fully seated and you're getting some blow by. Why don't you have the PCV in the passenger side valve cover?
Do I understand that you have a PCV valve installed in a valve cover and no oil baffle underneath it?Hello all,
We have a freshly rebuilt 289 (60 over now) that is running smoothly. The cam was just broken in, and the car now can move under its own power (first time in 5 years). Before this rebuild, we had PCV from the passenger side into the air cleaner. Now, we have it coming from the driver side into the back side of the air cleaner, so it is a long hose run going towards the back of the air cleaner.
With this current set up we have been seeing a light amount of smoke (or oil mist from what I have researched) coming from the breather cap. We never had this issue before the rebuild. I have read in previous threads that it could be bad valve seats, or bad piston rings. The engine is as brand new, and the cylinder heads have a hundred miles or less on them. I would be so disappointed if either of those were the problem here.
This set up has worked before, and I am thinking this long (at least 14-18") run could be a part of poor PCV flow making it go out of the breather instead. Can you run two PCV hoses in one system? Should I replace the breather cap with a solid one?
Right now, the baffle on the PCV valve cover is NOT installed. Again, no issues before, but I can re install if needed. Let me know if you need any other information to provide the right answer.
...yes that is the current set up. It was taken out years back and I do not remember why. Possibly because the valve sunk too far in the valve cover and it touched the baffle? I'll be putting that baffle back in.Do I understand that you have a PCV valve installed in a valve cover and no oil baffle underneath it?
I had hired a dude off craiglist to help with the heavy lifting on the engine install. He also did the valve tuning and did a fantastic job. It was his idea to have the valve covers as they are (he was a Pontiac guy). I will need to swap the valve covers as they have different sized holes on them for the breather and the valve. I knew it was different at the time but was not thinking ahead about the PCV set up.Usually it’s PCV in the passenger cover, with a baffle under the valve, with hose to the manifold and breather on driver’s side, with hose to air filter or just a breather cap. Sounds like your long hose/intake setup is not pulling enough vacuum to make it work, provided there are no other issues (rings, etc). Non-PCV side should be sucking air in, not breathing oil mist out. Solid cap is not the answer.
Outside of the cam break in, what is needed to ensure those rings are seated correctly? Ill be making the switch on the valve covers today so I can have the PCV go on a much shorter run.Possibly the rings in the new engine are not fully seated and you're getting some blow by. Why don't you have the PCV in the passenger side valve cover?
So this is where Im confused…. The air cleaner, reguardless of the name, does not filter any air going to the breather. The breather has its own air filter inside at least the stock style does. You wont get any cleaner air into the crank case with a closed PCV system. But like Bart mentioned above the benefit is that when the engine is turned off the fumes that would otherwise leave the breather cap go into the air cleaner reducing pollution. Hence when the closed system was a California only thing. But the filter inside the breather also greatly reduces the vapor transferred into the air cleaner. In the end Im not sure there is a major difference here.The PCV system on my 67 289: PCV valve in passenger side valve cover (has baffle), connected to the back of the carb for manifold vacuum. Breather cap in driver's side valve cover connected to the air cleaner. I believe this is a closed PCV system.
I like having the breather cap connected to the air cleaner as it brings in filter air into the crank case. I live in AZ and we have a lot of dust here.
Ok either way for dusty environments the air filter wouldn’t filter air going to the breather cap. The air would have to go through the air filter then fight the vacuum from the carb and get pulled into the breather cap… I just dont see this happening. If anything the closed system would filter less.^I don't believe closed breather caps have filters inside them. And if the stock ones did it certainly isn't doing its job after 56 years.
"what is needed to ensure those rings are seated correctly?". Typically, it takes approximately 500 miles of varied speeds for the rings to begin taking a "set". Might take a little more or little less. It depends on the type of ring and the cylinder finishing process. Most standard "street" rebuilds follow the 500 mile rule.Outside of the cam break in, what is needed to ensure those rings are seated correctly? Ill be making the switch on the valve covers today so I can have the PCV go on a much shorter run.
The guy I hired to help with the engine install though this set up was best, but I did not have the foresight to think about the PCV.
So in theory I agree the air filter for the carb would filter both the air going into the carb and the breather. However this is only true if the air for the breather is being pulled from behind the air filter. I have never seen a 1965 or 1966 mustang with a air filter that fits snugly inside the air cleaner. In fact the ones NPD sells are quite small.The breather cap is connected to a fitting on the base of the air filter. This fitting is on the inside (carb side) of the air filter so the breather cap (PCV system) is sucking the same filtered air going into the carb. Closed PCV system:
View attachment 841736
A breather cap that is not connected to the air filter base is just sucking in outside air. Open PCV system.