What would you expect to happen if the breather line from the CAI to the crankcase was completely plugged (as in getting no air through whatsoever)? What would/could driving thousands of miles with this condition cause?
Well... that would be the "intake" side of your PCV system right? So I'd guess that you have a little bit more crap in your oil that might have been vented otherwise. That's mainly nasty gasses that are an emissions concern so I would expect very little extra particulate matter. And possibly a teeny tiny bit of water in there from condensation that didn't get vented when the oil got hot. Change your oil and filter and I think you'll be fine. If you're really worried about it take a sample and send it to BlackStone Labs for analysis. Tell them what happened and they'll tell you how much (if any) worse it is than normal. Now, we got to ask... just how does that line get completely "plugged"?
Quick: Thanks for the input. I send all of my oil samples to Blackstone and at least the last two were from oil with the car operated in this manner. There was nothing unusual noted on either analysis. CAI tube had the breather line fitting welded on to it but never had the hole punched out of the tube to allow any air at all to flow. Breather line came off the crankcase and the hose lead directly to a steel pipe dead end. You ain't sh!ttin' about vacuum. Oil fill cap could not be removed at all there was so much vacuum. Motor was trying to suck in air from wherever it could. It was squealing like a pig. Could this have lead to low oil pressure? I was seeing 17lbs at idle and nothing like that since I disconnected the hose. If there is a couple of HP gain with this condition, would you want to plug that breather when you are at the track?
Now that's an interesting question... The oil is a closed system. Gets pumped out of the crank case and returns to the crank case. So if the whole system is under a vacuum it shouldn't effect it's function (the oil should still get pumped through there the same). Unless things have changed from years ago, the oil pressure sensor has one side in the oil system and the other side outside. So it would be measuring oil pressure relative to outside air pressure. That's different than measuring the difference between pressure at the pump and pressure at the return. So relative to outside air pressure your oil pressure would read lower due to the vacuum the whole system is under, but I would expect the difference in pressure at the pump and pressure at the return to be the same as normal. that make sense?
Just keep in mind having more then 10 inches of vacuum on the crank case isn't a good idea on a street motor. Haveing said that,,, 6.1 based engines with the oil squirters will be fine. I would limit it to 10 inches of vacuum on a 5.7 based engine. Without oil squirters, to much vacuum can starve the rist pin of oil. We have been using the pcv system to create crank case vaccume for 3 yrs on our blown 392. The crankcase vacuum will follow engine vacuum. With a sort of time delay result. We also have a pcv valve (going the other way) to vent pressure under boost. It's been working great. With the 6.1 cam 18 inches of vacuum. It would make the engine squeal from one of the seals. So,, we had to limit the amount of vacuum. Since the Hellfire's 14 inches of vacuum. No problem.
I understand what you are saying. I would see the low oil pressure at idle only occasionally when I had run the car for long periods of time. The large majority of the time it was normal. Here is how I found it. The car would have a high pitch squeal or whistle while idling. It would happen a few minutes after start up but it would go away. Then if I would wait long enough, it would come back and then eventually go away. It sounded like it was coming from the area of the belt but when you got up close, you could tell that it was not a belt squeal. It was getting worse over the last 3-4 days. I don't know what made me try to take the oil fill cap off while it was running but I tried and I could not get it off. So, I pulled off the breather hose and "shwooooooop" like I broke the vacuum but the high pitch sound immediately went away. Then I shut the car off and put it back on and started it again. If I waited only a few minutes, I could get the oil fill cap off but I still got the "shwoooooop" sound. It was obvious there was a strong vacuum effect there. Then I disconnected the breather hose from the CAI to see if something was plugging the hose - nope. Then I checked to see if something was plugging the breather hole in the CAI tube - nothing plugging the hole because there wasn't one. I guess the high pitch sound was the motor trying to suck air through any place that it could (gaskets, seals?). I think that once is got some air from wherever, the sound would go away for awhile but eventually come back.
