My car has ran like shit for a long time. I stumbled on a thread a while back that shead some light on the situation and decided to expierement. I have a breather in my oil filler neck that has been cut down for looks. The car is boosted of course, and I still have the PCV valve. It's a 5.0L Ford.

For testing purposes, I put a vacuum cap on the PCV nipple and shoved a bolt in the vaccum line to the manifold. Starting seemed easier, the car ran better it seemed. This would make sence due to the removal of a vac leak.

Is it a bad idea to completely remove the PCV valve and seal the manifolds provision off and just run through the breather? What negative effect would this have? If you argue for not running the breather, please elaborate as to how I could make my stock PCV system perform better.

 

PCV is an emissions thing. Blowby gasses and oil fumes accumulate in the crankcase, and they have to go somewhere. If your crankcase isn't vented, you'll blow out gaskets and get oil leaks. If you just run filters, you won't develop pressure in the crankcase so that would solve that problem. Stock cars run the PCV setup so all that unburnt fuel and oil fumes get sucked back into the motor and burned, instead of venting to the atmosphere. There will be no difference between running the PCV or running filters on the valve covers, besides letting unburned hydrocarbons into the air. I'm not sure if they check for a PCV system when having your vehicle inspected, I'd imagine they do, but you could always hook it back up when you go in for inspection. I'd just run filters on both V/Cs if I were you.

 

what if oil is coming out of the crankcase while in boost through the breather? this is a situation i've run into. i "fixed" it by addind a good sized oil catch can using crank case vent hose from the driver side crank case and then putting a breather on the outlet of the can as to release the gases but no longer the oil that is getting, what seems to be pressurized under boost which is what is causing it to squirt through the breather while in boost. anyone know anything about this. a compression check showed the motor was fine so i don't think the rings are messed up, and there is no burnt oil coming out of the tailpipes so i don't believe i have blow by. what do you think?

 

Do you run baffles in your valve covers? I've heard of this several times, but never noticed if they were running baffles or not. I have stock baffled covers, I haven't driven the car yet but within a week or so it should be road worthy. I'll let you know if I see any oil seepage. It is entirely possible that a breather would get saturated with airborn oil over time and start to weep oil, but that wouldn't be a 'turbo only' phenomenon. The only thing I can think of causing a boosted engine to produce more airborn oil would be pressure pushing past the valve stems and coming up through the oil in the valve covers. In that case a catch can would be neccesary, but that would be an easy addition. There are also threads around here about keeping a functioning PCV system on boosted engines, using PCV valves from stock turbocharged motors. The only thing I don't like about those is under boost there is no ventilation for the crankcase(unless you route the PCV pre-turbo, no thanks!). Personally I'll run a catch can if I start seeping oil.

 

yeah i just installed an HKS oil catch can. i haven't really tested it yet, but i'm sure it'll work as the oil has no where to go but there now. in the middle of a transmission rebuild at the moment so the fun is being postponed. still, i'm very surprised that there is that much extra pressure from only 6lbs of boost.