Smoking: catching oil from PCV line on a 408 Magnum

[jbc426]

I was getting significant smoking during high rpm especially during hard upshifts on my fresh ( < 150 miles) 408 stroker motor that is based on a 2001 5.9 Magnum block. I was praying that it wasn't the rings not seating. It didn't smoke at all at low or moderate rpm, and it wouldn't do it between the 1st and 2nd gear upshifts. I could see a cloud of smoke in the rear view mirror after a sustained wide open throttle application as the transmission automatically upshifted into 3rd and 4th.

Turns out the motor was sucking a significant oil mist from the PCV valve/line. I bought an in-line air compressor water/oil trap and installed it in the PCV line that goes from the PCV valve to the intake manifold. It took a few minutes to install, and in one day already captured a thimble full of oil. The smoking stopped completely once I installed this. I opted for a quality trap/filter and with new line and good hose clamps, it cost me about $60.

I was surprised at the volume of oil that had been going into my intake tract, and pleased that my rings are seated. The motor seems to idle a little crisper now too, but that may be my imagination.

 

[stroked340]

Well your smoking might have stopped because of what you did..but whats causing the smoking??? sounds like a band-aid to a bigger problem..

 

[EL5DEMON340]

Do you have a big baffle under the PVC valve? Bottom side of the valve covers should have provisions for it.

 

[jbc426]

Do you have a big baffle under the PVC valve? Bottom side of the valve covers should have provisions for it.

Good point. There is a small baffle under the PCV cutout, but it is very small. When I do a valve adjustment check, I'll install a larger one.

 

[jbc426]

Well your smoking might have stopped because of what you did..but whats causing the smoking??? sounds like a band-aid to a bigger problem..

I'm getting absolutely no smoking anymore at this point, but I suspect the air cleaner hat I'm using to get more hood clearance may be causing an air flow restriction at high rpm, which is causing higher than normal vacuum. This combined with too small of a baffle under the PCV valve may be the underlying issue.

 

[TrailBeast]

I ran across the same problem, and I do have baffles in the cover so I put a 1/8 limiting orifice inside the PCV hose to slow the vacuum down and that took care of it.
It will still vac your hand to the opposite valve cover vent but the smoke went away.

The PCV is supposed to be nearly closed at WOT anyway, so you may have run across a bad valve that does not.

 

[jbc426]

I ran across the same problem, and I do have baffles in the cover so I put a 1/8 limiting orifice inside the PCV hose to slow the vacuum down and that took care of it.
It will still vac your hand to the opposite valve cover vent but the smoke went away.

The PCV is supposed to be nearly closed at WOT anyway, so you may have run across a bad valve that does not.

That is what I thought too. At wide open throttle, there should be very low or no vacuum reading, so the PCV valve should not really be suck that much air at that point.

This was only happening at high rpm's in the 4800 rpm to 6500 rpm range in the top gears. I may put a fresh valve in just in case. I also have an open element breather on the opposite valve cover, which should vent excess vacuum.

Either way, I'm happy it is not smoking at all anymore. I'll flog it plenty more in the following few hundred miles of my break-in period, then put in a bigger baffle and fresh PCV valve, install a larger intake-to-airfilter hat, make sure everything is tightened up and change the oil and filter.

I read numerous articles about this issue after doing some research on Google. Sucking oil into the intake through the PCV system turns out to be not that uncommon of a problem at high rpm or when a motor is boosted via supercharging or turbo charging. I suspect the restrictive air hat and too small a baffle in the valve cover are contributing factors.

.

 

[TrailBeast]

That is what I thought too. At wide open throttle, there should be very low or no vacuum reading, so the PCV valve should not really be suck that much air at that point.

This was only happening at high rpm's in the 4800 rpm to 6500 rpm range in the top gears. I may put a fresh valve in just in case. I also have an open element breather on the opposite valve cover, which should vent excess vacuum.

Either way, I'm happy it is not smoking at all anymore. I'll flog it plenty more in the following few hundred miles of my break-in period, then put in a bigger baffle and fresh PCV valve, install a larger intake-to-airfilter hat, make sure everything is tightened up and change the oil and filter.

I read numerous articles about this issue after doing some research on Google. Sucking oil into the intake through the PCV system turns out to be not that uncommon of a problem at high rpm or when a motor is boosted via supercharging or turbo charging. I suspect the restrictive air hat and too small a baffle in the valve cover are contributing factors.

.

My passenger side valve cover has the PCV at the back end of it and my drivers side cover has a cap that is plumbed over to the air cleaner.
Of course I had to make that way.
I wanted the PCV, but it had to be filtered air that was pulled into the engine, so with the use of PEX leftovers from the house this is what I have.
That ring is NOT going down my intake if it ever comes loose.

 

[jbc426]

I like it. Filtered air is the only thing that should be allowed to flow into the engine. My breather cap has a foam element that air has to pass through before it enters the engine. It has a very low restriction, and allows for air to go in or out.

With an opening like that, it's hard to believe how much oil makes it into my oil trap.

 

[Marcohotrod]

a pcv valve is best mounted at the front of the cover, not rear, with a large baffle, on a high accel. vehicle. the breather does not "vent excess vacuum" , it vents pressure when the pedal is to the floor and there is little to no vacuum

 

[jbc426]

a pcv valve is best mounted at the front of the cover, not rear, with a large baffle, on a high accel. vehicle. the breather does not "vent excess vacuum" , it vents pressure when the pedal is to the floor and there is little to no vacuum

Good tip. My breather is just a simple push-in filter that fits in a a hole in the valve cover. It can let a given amount of pressure out or allow some air in to reduce vacuum, so yes, it can vent excess vacuum. Symantics.

 

[TrailBeast]

a pcv valve is best mounted at the front of the cover, not rear, with a large baffle, on a high accel. vehicle. the breather does not "vent excess vacuum" , it vents pressure when the pedal is to the floor and there is little to no vacuum

My PCV pulls vacuum in the case and the breather on the other valve cover lets filtered air into the engine to evacuate building gasses and cause a light vacuum under normal driving conditions.
Also since the holes are made into the fabbed aluminum covers this way, it's staying this way.

(Daily driver here, not a race car)

 

[moper]

The right "fix" would be to properly place and baffle the pcv hole in the valve cover. But, I said "fix" because you may not have fully seated the rings yet. If the wall finish is right, moly rings seat almost immediately. If the wall finish is rougher, even by a little, they will take time to seat just like plain iron faced rings. I'd just give it some miles. While it is helping, finding odd stuff under the hood always send up red flags if I'm looking at a car.

 

[jbc426]

The right "fix" would be to properly place and baffle the pcv hole in the valve cover. But, I said "fix" because you may not have fully seated the rings yet. If the wall finish is right, moly rings seat almost immediately. If the wall finish is rougher, even by a little, they will take time to seat just like plain iron faced rings. I'd just give it some miles. While it is helping, finding odd stuff under the hood always send up red flags if I'm looking at a car.

Good advice, thanks. The motor has about 4 tanks of fuel through it now. It runs really good and is showing no signs of smoking. I changed the Dyno oil and filter after the initial start up with more dyno oil and a fresh filter. I'm going to change it again soon and continue to run run conventional oil for the first 2 or 3k miles. Then I'll switch to synthetic.

I have not done a compression or blow-down test, but the smoking seams to have ended completely.

I PM'd Mike at MRL regarding a comment he made to another post, " You have to run some sort of breather on the VC and a PCV as well or the crank case pressure is going to go sky high." to get clarification as to whether or not this a result of bad ring seal or it's normal to have pressure build at high rpm.

When I double check my lifter preload, I'll add a better baffle and swap my cast valve covers to the opposite sides. This will address the positioning of the PCV valve to the front of the engine. I'll bypass the oil trap and check to see if that also eliminates the smoking. If so, off comes the oil trap.

 

[moper]

Good moves.
There's always some crankcase pressure because no engine seals 100% of the combustion pressure. As rpms rise the number of firing events per second go up, so more compression leakage per second, while the path for that pressure to escape stays the same. Eventually the top ring gets pushed off the ring land by gasses below it and that's where things really get ugly and seal is lost. That's why vacuum pumps are good to have on race engines. It increases ring seal and raises the rpm capability. Sometimes the PCV is not enough but in most decent engines it's more than enough. You see race cars losing the PCV to reduce oil contamination and leaning out of certain cylinders that can come with it.