I have been seeing enough crank pressure to partially pop my dipstick out. This leaves any vapors and pressures that build up during a 140mph run down the straights to exit exclusively out the exhaust side tube.

Under boost, the PCV valve is essentially acting as a plug for the intake side tube at best and at worst is pressurizing the crank a bit with boost pressure that leaks by. The '90MSM motor spend a significant percentage of its time under boost on the track. I have my own questions about a catch can design. That design is badly flawed for reasons that has been covered 1,000 times. The MSM design attempted to collect and condense that vapor into liquid oil and return it to the oil pan. The basic design is intended to suck (vacuum) vapors out of the engine and burn them in the combustion process. There are baffles inside the cam cover but both sides are essentially open to each other. Is there anyone else out there who wants to throw their 2c worth in? Test -> Let the car warm up, then hold some plastic or your hand near the small filter on the intake side for a while (maybe rev the engine a bit too) and see if there's any oily residue. Have you had a look to see how saturated that small filter is with oil? (I'm actually genuinely interested!) So the question, in your case, is why bother having a catch-can at all if you're only going to scrub some of the vented crankcase air? This is to atmosphere via the intake side vent and it's small filter. The way your system avoids this problem by having an alternative path for the crankcase pressure to vent. I would also add it would be better to have the return line from the catch-can routed to a point between the filter and turbo (but after the MAF if it still fitted), this is how the return for the factory catch-can is plumbed.ДЄs you have it currently set up, with the return plumbed back to the intake plenum with a PCV fitted, when the car is on boost the PCV will be closed thus causing pressure to be trapped in the crank-case/catch-can system. I would expect the the passenger side vent will result in an oily residue being dumped all over your engine bay and the tiny filter will become completely saturated after a relatively short time. In effect one half of your crankcase venting is getting scrubbed by the can then returned to the intake path while the other side is being passed through a small filter (minimal cleaning) and then being vented into the engine bay. Some guys just seem to put a can with a breather between the 2 vents on the sides of the valve cover. Not saying you should do this, but its working OK for me right now. Maybe a photo will make it easier to understand. The can I got is definitely solid but its possible I'll have to change the routing of it all. I plan on running about 15psi to achieve my goals so I will report again after tuning. It was the only gasket to let loose, and probably because it wasn't an OEM gasket but a piece of cardboard cut to fit the space with supergray on both sides of it. We initially made a mistake of leaving the PCV in the valve cover which pressurized the motor and blew out the oil return gasket from the turbo. I'm not getting any oil out of the valve cover breather either. The can collected a LOT of engine assembly lube from the build, it looked like a george forman grill grease tray in there. I've tested it up to 5psi so far with no leaks and a totally clean return hose back to the manifold. Philly-Just curious.is this set-up new with the new motor or did you run this set-up prior to the rebuild? Only reason I ask is if the set-up has been fully tested under heavier boost conditions. If your can has a breather on it, it's not the same setup. My can doesn't have a bottom drain or fitting so we made a plate and closed off the return falnge on the pan. you will want some kind of check valve or PCV in this line to keep manifold pressure from pushing back up into the can Have the outlet hose from the can going into intake manifold. Lead your inlet hose from the exhaust side of the motor into the can (sealed can, no breather) To make it stay in place, I would recomend gutting the PCV valve and putting the breather on that It required 2 PCV valves (one gutted, one functional) and uses a sealed can. I've got a nice polished replacement Carbing strut tower brace with brake cylinder stopper ready to go in too. I'm more concerned that the inlet into the manifold from the PCV needs to be able to draw air for some internal function which I don't inadvertently want to stuff up, so to speak.ДЄs for the factory catch-can arrangement, I know it does work ok with some modification, it's just that it's so ugly and simply must go! Thanks for the link millsj, so others have done what I plan, albeit with track cars.

How to install oil catch can in miata