PCV elimination... Vacuum or SlashCut?

So I've read and read and read... And thought about this for a couple of weeks now.

What really got me going on this was my drive to NE about a month ago... I took the 88 accord out and had some silly pcv issues will cruising 80 in my 1st gen Teg gear sets (which puts me at near 4k @ 80mph). I do NOT have my valve cover hooked up to my air intake (which in hindsight seems like it might have been a decent idea for the drive). during the drive i noticed a faint oil smell that would eventually led to a smoky cabin whilst driving... being the worrier that I am, i pulled over to get some gas and notice that my vc was dumping oil on occasion out onto the rear mount. to further this i noticed it getting worse when i decided to pull over in some 1 gas station town to inspect my PCV valve. after removing the little guy i noticed that it was completely stopped up. so with no parts house anywhere in sight, i decided that i would try and clean it with some wd-40 from the gas station (wd40 wouldnt be my first choice btw), I got it loosened up some and drove to omaha, where Jared was waiting for with a new PCV valve!! This had me thinking about trying to reconfigure the PCV systems on these cars...

To make it worse, I have not legit PCV system on my red lude, just a vented pcv box and a vented vc...

Now i've been reading lots about the vacuum pump and the slash cut kits, and was totally leaning towards the vacuum pumps (due to the negative info on the slash kit) until i read a very well written article on a big suby forum. One of the big negative things floating around out there about the slash cut kits is that even with a vacuum gauge hooked up, high rpms where pulling no vacuum at all... But the suby forum (written by a shop owner with a 500+awhp sti) noted that if the crank case was properly vented that it would be extremely hard to get measurable vacuum out of the crank case, that in order to get measurable vacuum there would have to be an "end" to the crank case, sealed up if you will, and that the whole point of the system is to get the air moving out of the block. and that the best way he could tell that it was making a difference (other than not blowing every seal out while running a gt35r on 26psi) was that at 4500rpm coming instantly off boost, he'd pull 25" of mg on his boost gauge which is a little more than 5" more than previous do the better sealing rings, and increase "suction" on the downward intake stroke!

I want to hear what you guys think, but in the very next post, i'm going to post up my idea for both the Red Prelude, and the White accord...

oh yea, and the best part about the moroso kit is that it comes with enough parts to do 2 4cylinders motors...

This is the Kit i'm looking at...

http://www.summitracing.com/parts/MOR-25900/

im thinking for the red lude... Get an oil seperator, ie catch can with two ports on it, convert the filter to another port, run the system just like 87roach did, but port the valve cover in two spots with two -10 an fittings. run the slash tube to the top of the resevoir like in 87 roach's setup, two ports to the vc and leave the crank case filter on the breather box, call this setup good.

On the white accord, install a port of some kind on the pcv box, run the slash tube directly to that, and slap a filter (left over from the red lude) onto the vc of the accord? anyone know which side would be better to put the vacuum on (vc vs block side?) it doesn't really seem to matter and in an effort to save money (on the white car) just using the accords existing pcv box as an oil seperator (much like it is supposed to be designed) Ideas? anyone?

why not leave the factory system alone,and just fix it, and add a catch can between the oil separator box and manifold? these cars actually have a pretty decent system. If you reduce it's efficiency, you are going to end up with dirty oil and sludge

On the red prelude this is not an option. Dcoe webers dont work well with factory pcv systems. The white accord currently isnt working very well, and it'd potentially be better and cheaper than running a catch can if im already going to buy the kit

I checked the kit out via the link you posted. What is the significance of the stated constraint...?

"Cannot be be used on vehicles with mufflers."

The description of the benefits sounds pretty good, except that most of us DO have mufflers of one sort or another.

For PCV, either of your methods should work. Basically you just need to create air flow through the crank case. Pulling from the VC might work slightly better as it could (maybe) take advantage of natural convection (warmer air tends to rise). That effect will be very small though.

Pulling a measurable vacuum though is a different story. To do that you would need to mostly seal up the crank case, or use a pump that has a pretty substantial flow capacity. For PCV the slash cut idea will work pretty well, but for pulling a vacuum I'm not so sure. It should have a pretty good flow *rate*, but I doubt it will be able to create much of a pressure drop. The only way to really test that would be to run the slash cut tube directly to a gauge (only) and measure the pressure.

As far as the slash cut kit not being used with mufflers, the only thing I can think of is that maybe there would be oil buildup in the muffler over a long period of time. The catch can should get most of it but it won't get it all. Whether or not this a legitimate problem I don't really know.


I like the idea of freeing up some power with crank case evacuation, and I'll probably try it someday. It's pretty low on the priority list though.


C|

Quote:

---

Originally Posted by hondalude86

This is the Kit i'm looking at...

http://www.summitracing.com/parts/MOR-25900/

im thinking for the red lude... Get an oil seperator, ie catch can with two ports on it, convert the filter to another port, run the system just like 87roach did, but port the valve cover in two spots with two -10 an fittings. run the slash tube to the top of the resevoir like in 87 roach's setup, two ports to the vc and leave the crank case filter on the breather box, call this setup good.

On the white accord, install a port of some kind on the pcv box, run the slash tube directly to that, and slap a filter (left over from the red lude) onto the vc of the accord? anyone know which side would be better to put the vacuum on (vc vs block side?) it doesn't really seem to matter and in an effort to save money (on the white car) just using the accords existing pcv box as an oil seperator (much like it is supposed to be designed) Ideas? anyone?

---

Quote:

---

Originally Posted by hondalude86

On the red prelude this is not an option. Dcoe webers dont work well with factory pcv systems. The white accord currently isnt working very well, and it'd potentially be better and cheaper than running a catch can if im already going to buy the kit

---

why not add a balance tube and pull pcv vacuum from the center of the balance tube? thats the way my carbs would have been set up factory. I can get you the part number of my pcv valve if you like, it's the one that would have originally been on the Datsun carbs, they were used on a lot of Datsun and nissan stuff, the advantage is the end that goes to the manifold has regular pipe threads. all you need is a balance tube and a threaded fitting in the center,then it will hook up like factory

the idea of adding oil fumes back into my intake seems like a bad idea.. I like the "kills trees and babies" method better. And if your going to go through all that trouble, how would it be better than the slash cut method?

Quote:

---

Originally Posted by hondalude86

the idea of adding oil fumes back into my intake seems like a bad idea.. I like the "kills trees and babies" method better. And if your going to go through all that trouble, how would it be better than the slash cut method?

---

most people add one of those compressed air oil separators between the intake and the valve, I'm not trying to be a tree hugger, this is one system you want to keep as it really helps keep your oil clean, it's not just the blowby products you want to worry about, it's also the moisture that builds up as a normal combustion byproduct, this moisture combines with the combustion byproducts and forms acids and also create sludge. If you've ever worked on an old engine that didn't have a pcv valve, you would be amazed at the amount of crap built up inside of it.

but still, wouldn't an catch can with slash cut really not work as good as trying to rig up some other form of PCV which would either still require a catch can, or run the oil laiden air back into the carbs?

To get the blow-by gasses out of the crank case all you need is a way to create air flow through it. The OEMs run the vapor back into the intake because it's essentially self cleaning. The trick to removing the oil/water vapor from the gas is to cool it down so they can condense out. That's what the catch can does. The stock oil separator box does the same thing but after many years they get plugged up with carbon and don't work so well.

For the Accord, the easiest thing to do would be to connect the output of the breather box (that normally goes to the PCV valve) to a catch can. Put a PCV valve on the top of the can and then run that to the normal PCV port on the manifold. The valve cover gets a breather filter or just run it into the stock filter box. This way there is minimal modification to any stock parts (easy) and it will work.

On the red 'lude, the slash cut tube is probably the way to go. If your manifold has a vacuum port for each runner you could try tee-ing them together and use that as a vacuum source for a PCV valve. Thing is that might mess with the idle setting so you would have to play around a bit, possibly adding some extra restriction to keep it from being too much of a vacuum leak.

As for the Moroso kit, I wouldn't bother. All you need is the slash cut tube (which you can make) and the check valve (which you can get separately).


C|

Quote:

---

Originally Posted by cygnus x-1

To get the blow-by gasses out of the crank case all you need is a way to create air flow through it. The OEMs run the vapor back into the intake because it's essentially self cleaning. The trick to removing the oil/water vapor from the gas is to cool it down so they can condense out. That's what the catch can does. The stock oil separator box does the same thing but after many years they get plugged up with carbon and don't work so well.

For the Accord, the easiest thing to do would be to connect the output of the breather box (that normally goes to the PCV valve) to a catch can. Put a PCV valve on the top of the can and then run that to the normal PCV port on the manifold. The valve cover gets a breather filter or just run it into the stock filter box. This way there is minimal modification to any stock parts (easy) and it will work.

On the red 'lude, the slash cut tube is probably the way to go. If your manifold has a vacuum port for each runner you could try tee-ing them together and use that as a vacuum source for a PCV valve. Thing is that might mess with the idle setting so you would have to play around a bit, possibly adding some extra restriction to keep it from being too much of a vacuum leak.

As for the Moroso kit, I wouldn't bother. All you need is the slash cut tube (which you can make) and the check valve (which you can get separately).


C|

---

remember the stock oil/air separator also keeps you from losing oil to the pcv, it picks up oil vapor at the back of the pan, then the oil simply condenses out, and runs back into the crankcase through the port in the back of the engine, it's the same oil passage that returns oil to the pan from the head. When I modified mine I didn't see any kind of carbon, it's just a metal baffle in there, the oil adheres to the baffle and runs back to the oil passage, it's no different then inside of the oil pan or inside of the valve cover, there is also a baffle built into the top of the valve cover itself

Quote:

---

Originally Posted by lostforawhile

remember the stock oil/air separator also keeps you from losing oil to the pcv, it picks up oil vapor at the back of the pan, then the oil simply condenses out, and runs back into the crankcase through the port in the back of the engine...

---

Right. An external catch can is really just an extension of that separator box, with the difference that you don't return the oil back to the oil pan. I guess you could return it though. Either add a return line from the can to the oil pan port, or just empty the can occasionally and dump that back into the engine.

C|

Quote:

---

Originally Posted by cygnus x-1

As for the Moroso kit, I wouldn't bother. All you need is the slash cut tube (which you can make) and the check valve (which you can get separately).

C|

---

As Cygnus said, I wouldn't bother with the kit unless you are planning on using both of the valves.. otherwise it will be cheaper to just buy a single tube and valve(like I ended up doing). I think I posted up what parts I ended up using, if not I can get some details for you.

Once I get the car going, then I will be able to tell how good the system I built works!

sounds great guys, thank you!!! I've got a lead on a potential catch can for cheap, so before i go AN fitting crazy, i'm going to for sure wait to see how that goes. Knowing what I know now, I will just buy the slash tube and a ford 1way valve. Seems like this is jusy going to be installed on the Red Lude, so i'll get cracken after the current Red Prelude Project is done.

I just run without PCV installed have a breather in the top of the catch can on the block and breather on the VC, as you say get a slight oily smell but nothing really bad only notice it when stuck in traffic on the move no real difference the stench of fuel from the carbs tends to overwhelm that more!! lol!!
As for sludge buildup, from the 15 years I've been running webers I've never noticed any issue with sludge buildup or oil problems, I think this was more of an issue using cheaper mineral oils, with a good semi synthetic or fully synthetic which have a lot of cleaning properties in them this is not going to happen. I also change the oil pretty regular as well every track day or every few thousand miles which is normally once a year with the limited miles I do as it's race car not daily driver. If it was a daily driver I'd certainly probably have some sort of PCV system in place.

This is my current setup rich, gio got video of the car on the dyno with his good camera and you can see it smoke pretty good out of the vc.

Whats the temps like outside if it's still cold mostly could be steam mine was when i took it for a spin. Otherwise it's pretty nominal and on a race car not worth worrying about too much. Depends how often you going to be driving the car and for howlong each time I guess. Other option is to use a remote catch tank and have the breather placed somewhere out the way where it's not going to get sucked into by the air intake for cabin. Or maybe look at sealing up the bonnet area better so it doesn't come out the bonnet but gets pushed down and underneath the car.

I think the temps where in the upper 60s low 70s, but low humidity. What is your take in proper ring sealing rich?

My take on engine bedding in is use cheap oil for first bit drive gently for first few hundred miles to get the bearings run in, and then drive normally for a 1000 miles with a few spirited short bursts to help seat the rings. After this new oil but still semi sythetic cheap stuff and just drive it normally but with more sustained full throttle and general full load when ever you want after couple more thousand miles should have loosened up nicely and should get good compression.

now this is on a engine I would build for long term use of if the car was new.

If it were mine I'd give it a few hundred miles of easy light use to bed everything in then few full throttle runs for a couple more hundred miles then it would be a case of driving it like your stole it as it would be straight to drag strip or race track soon after!! Normally notice a nice boost in power after 700-1000 hard miles as rings bed in properly then I'll stick the synthetic stuff in!! I'm guessing as your's has gained 5whp sounds like your's has just bedded in. what was your last compression reading like when you tightened the H/G up to stop the leaking.

When you get it bolted up next make sure you heat cycle it a few times then retorque the head down to around 65-70lbft. If the head is flat and block is flat then it's a bit worrying as to why it had gone, I know it overheated but I'ld be very carefull to check both surfaces and I'd still get the head milled to be safe and also to get a nice clean surface try and make sure it goes to machinist that can put the smoothest surface on it as possible last one I used it was nearly mirror polish it was that good!!

Hmmm quite warm already then were still hovering between 6-10 degree's although the other week we nearly hit 20 degrees!! But that's quite rare for this time of year normally!! Should start getting a bit warmer from next month onwards 12-20 degree's and summer normally 24-28 degree's sometimes around 30 degrees C if we get a bit of wind from Spain and Med Ocean.

you really should look for some of the oil with the zinc phosphate in it, it's out there just do some searching, companies make it just for people with older engines,I would break it in on that oil