Catch Can with or without PCV? Which is best?

[shelbydoug]

I'm also till thinking about running a catch can.    I'd like anyone's thoughts and experience in running a closed system (no breathers on the catch can) vs an open system (with breathers.)

Personally I would install one of the cheap catch cans, like I show in reply #6, just to get a quantitative idea of how much oil is getting through the PCV and into the intake via the spacer connection. You can plumb it in using stiff hosing and you won't have to attach it to anything, the hose will keep it in place. You're welcome to borrow my setup if you like, just let me know.

Don't know if it would help but I think in your situation you can connect the PCV to the rear of the intake and take the valve cover siphoning out of the equation. There are kits for FE's like this:

https://www.ebay.com/itm/284265816138

I don't have any experience with the open catch cans but there are lots of choices if you want a PCV connected oil seperator. I chose the Bob's Machine unit due to it's very good reputation and haven't been disappointed.

Dave

ALL excellent questions to ponder of which proportional thought will be applied to. 

Here's one for you. Do you have to sleep only on the right side of the bed?

[s2ms]

Here's one for you. Do you have to sleep only on the right side of the bed?

Well yes, the correct side! 

[Side-Oilers]

Thanks guys.  Great advice.


Should I keep the PCV in the valve cover, or install it in the "rear of the manifold" location, which is currently capped off?


The Bob's Machine catch cans look like a good product.  I'll try it. Thanks.

[2112]

Impressive that a pristine Autolite cookie cutter valve cover cap has been drilled for a PCV connection.

[Side-Oilers]

I'm using a Bob's Machine oil separator on my 66. Otherwise stock PCV valve and closed breather setup. Works great and fits with no modifications, the bracket is attached to one of the export brace bolts. Probably overkill at this point as I finally was able to fabricate a baffle that is working well, originals were removed to fit roller rockers/polylocks, but it still does catch some oil so keeping it installed for now. I used repop PCV hoses and cut to fit.

Thanks for the photo.  My Kirkham doesn't have that much space to mount the Bob's can, but I can hopefully fab something that will work.  I now understand the idea about having the can higher than the carb vacuum port. 

[Side-Oilers]

Impressive that a pristine Autolite cookie cutter valve cover cap has been drilled for a PCV connection.

It's not NOS.     

Drake, I think.  I like the look of it better than a bunch of other options on the market.   Plus it says "Autolite"  Cool 

[shelbydoug]

I'm using a Bob's Machine oil separator on my 66. Otherwise stock PCV valve and closed breather setup. Works great and fits with no modifications, the bracket is attached to one of the export brace bolts. Probably overkill at this point as I finally was able to fabricate a baffle that is working well, originals were removed to fit roller rockers/polylocks, but it still does catch some oil so keeping it installed for now. I used repop PCV hoses and cut to fit.

Thanks for the photo.  My Kirkham doesn't have that much space to mount the Bob's can, but I can hopefully fab something that will work.  I now understand the idea about having the can higher than the carb vacuum port. 

Personally I'm not completely sure of what the exact combination is to break the siphoning effect. Everything mentioned seems to help some

My experiences at the moment are on the small block and the Cleveland. My 428 is still on the engine stand but one of the subjects discussed on the 67 GT500 engine is why was the pcv hose plumbed to the bottom of the air cleaner base rather then the vacuum port on the intake?

I speculated that perhaps this "issue" of oil siphoning isn't imaginary and the quick fix was the hose relocation? Maybe that is in effect a stroke of genius? 

I'm thinking that maybe before emissions wasn't such a big issue, some oil in the intake wasn't a bad thing? Thinking of the original Ford system of using those rubber umbrellas on the valve stems, it seemed to be just a system of reducing the quantity of oil to the valve stems rather then eliminating it?

[2112]

Impressive that a pristine Autolite cookie cutter valve cover cap has been drilled for a PCV connection.

It's not NOS.     

Drake, I think.  I like the look of it better than a bunch of other options on the market.   Plus it says "Autolite"  Cool 

I had no idea Drake made them. It looks good. Kudos to the machinist who cut the hole without  fubarring it.

I bought two real NOS caps. Don't ask how much.   

[Bob Gaines]

Impressive that a pristine Autolite cookie cutter valve cover cap has been drilled for a PCV connection.

It's not NOS.     

Drake, I think.  I like the look of it better than a bunch of other options on the market.   Plus it says "Autolite"  Cool 

I had no idea Drake made them. It looks good. Kudos to the machinist who cut the hole without  fubarring it.

I bought two real NOS caps. Don't ask how much.   

Don't feel bad about your purchase just yet. The one that Drake sells in ether black or chrome is the the 70's style cap with a hole and not the closed emission cap like 67 thermactor cars used. FYI the one's used on 67's typically were plain and not marked with Autolite .

[2112]

Impressive that a pristine Autolite cookie cutter valve cover cap has been drilled for a PCV connection.

It's not NOS.     

Drake, I think.  I like the look of it better than a bunch of other options on the market.   Plus it says "Autolite"  Cool 

I had no idea Drake made them. It looks good. Kudos to the machinist who cut the hole without  fubarring it.

I bought two real NOS caps. Don't ask how much.   

Don't feel bad about your purchase just yet. The one that Drake sells in ether black or chrome is the the 70's style cap with a hole and not the closed emission cap like 67 thermactor cars used. FYI the one's used on 67's typically were plain and not marked with Autolite .

Ahh,

I do feel better now. 

[pbf777]

Should I keep the PCV in the valve cover, or install it in the "rear of the manifold" location, which is currently capped off?

     The answer is: it depends!   Aesthetics aside, although every engineering attempt should include this consideration, I would advise on an FE mounted in a modern Cobra to have two "open" breathers mounted, one to each valve cover, of a type with baffling consideration for resisting oil loss to the exterior, and the P.V.C. valve inserted into the rear intake manifold breather opening also with the required baffling to impede oil entry into this plumbing.  Although this does provide a certain sum of symmetry, it's functional in that first as indicated previously the plumbing is routed uphill from the valve to the entry to the manifold which also as mentioned previously should be under the carburetor presenting particularly the oil contamination in the plenum area thereby dividing this sum among the cylinders and not the presentation into a singular inlet runner.

     In this layout initially at idle and low engine revolutions with reduced load the air flow routing enters the crankcase thru the breathers mounted to the valve covers, being one in each cover increases the available area reducing the velocity and drawing or shall we say flushing the unappreciated by-products of combustion fume and water condensation from both internal sides of the engine toward the P.V.C. valves' central mounting.  This presenting access to the crankcase thru the intake manifold valley cover is an area well shielded from oil throw-off from rapidly moving components.  But understand not immune as we currently have a 427 T.P. mounted on our dyno in which the assembler (not us!) failed to install the gasket for sealing between the tin valley pan and intake, in short order of operation one has a swimming pool of oil accumulating on top of the cover pan.

     As the engine increases in speed and load the blow-by sums greatly increase, soon to the point beyond the flow capacity of the P.C.V. plumbing and now these excessive sums are emitted from the "open" valve cover breathers, and this is the happening that creates the greatest incident of oil escapage and the point of need of typically as defined an "oil catch can".   Again this makes for sound intention as with the area of two "open" breathers velocity is reduced (vs. having only one), and other than oil directly thrown up the pipe (evidence of poor baffling) it is this velocity rate that effects the weight of the oil carried in the air stream and thru the plumbing, and as not to nitpick terminology, your not actually "siphoning the pan dry" as in a straw stuck in you soda can.  The breathers mounted high on the engine also aid in the separation of oil as the atmosphere being evacuated is emanating in path from lower in the crankcase where the heat and turbulence is greatest and the bulk of the mixing of the oil in the atmosphere takes place here and with the required lifting of this heavy mixture enroute to the valve cover mounted breathers much of the oil is permitted the opportunity to drop-out even before it becomes a concern for a reasonable attempt to baffle your breather system in an attempt to preclude the remainder escaping.

      The P.V.C. valve installations' greatest perceived value, in your street driven Cobra, is to reduce the obnoxious fume emanating from the breathers, this generally noted particularly with the engine (oil) hot, and say when at idle stopped at a traffic light, this can even perhaps escalate to the point of presenting a not so pleasing cloud about your vehicle that may not only be odifferous but not present the best presentation for your vehicle.  And yes, there is the benefit of "less" oil escapage and this rather messy presentation upon opening the hood, or if permitted even to the point of dripping on the ground, with the joking statements that your car is marking its' territory every were it's parked.  But again in reality the bulk of the oil carry-over whether external or in the plumbing, particularly of the "closed" venting systems, takes place when your on the throttle, and this is beyond what a properly intentioned P.V.C. system is designed to cope with.

      With a track car, I would eliminate the P.V.C. plumbing, then along with the valve cover breathers, utilize the rear manifold mounting for another crankcase breather outlet.  If permitted reasonably baffled to open breathers work best; sometimes you just can't improve on simple!  If plumbing to catch cans(s), as stated previously mount the reservoir(s) as high as possible, route the plumbing up-hill, particularly as closer to the point of the mountings on the engine (example: in the photo presented in reply #11, the driver side breather hose fitting is pointed in the worst way, down), and use the largest possible (reasonable) plumbing lines and fittings (again, (and he's going to hate me!) in reply #11, this is a minimal size hose in plumbing, but perhaps acceptable on a well sealed small block) as this reduces the velocity allowing the heavier oil mist to drop-out in the line, and if it's downhill to the valve cover, the oil will just drip back into the engine where it belongs.  Its' best to be diligent at keeping the oil out of the plumbing rather than trying to figure out what to do with it once it's here.   

      The problem with most of these cute, billet "bling-bling" catch-cans is that they lack enough internal area to create the velocity reduction required to make them function, and not enough effort in the baffling to make up for this, but perhaps often incorporating something that looks like a filter element(?) which it is implied "separates" the oil from the atmosphere, which it will to some degree, or is it that with the restriction created by this element, particularly once saturated, oil that contacts it is rather infused back into the air stream?  But we already have some previous statements made where they have found minimal remnants of anything, so how well is this working?  Or, was it really needed to start with, so how good does it really need to be?  And then if it were to capture any real volume they lack any capacity for storage, which further defeats their abilities.  Also, if a track car with any great singular on track duration time intended, plumb the catch can canister drain back to the engine (oil pan?) as if you are "siphoning" the oil out of the engine, it will also be automatically flowing back in and not draining the pan.      

     Scott.

     

[Side-Oilers]

^^^ Scott, that is an excellent explanation of the process and the benefits/downsides of PCV vs no PCV.   

When I bought the car, it had only a breather on each valve cover, and on the back of the manifold. No PCV system. This was with the pre-rebuild aluminum FE with 482 c.i.

It ran well on Willow Springs, and aside from pushing some oil out of each valve cover breather and onto the headers, it seemed okay.

On the street, however, it gave off oil smell when at a stoplight.  (Again, this was with No PCV.)


With the rebuilt aluminum 482 (now 483 c.i.) the same breathers and the same No PCV gave heavier smoke/odor on decel (than before rebuild) as I described in my original post.  Much more of both on the right side...thus that's where I chose to mount the M/E Wagner PCV valve in attempt to mitigate the problem.

But, I have learned from your posts that the downhill flow of the PCV to the vacuum port is probably a big source of the problem.


So, I've been monkeying around it, as described, with some gain, but it's not even close to my liking. 

The engine only has about 500 miles on it.  Any thoughts about a ring in the right bank not being fully seated?

If so, what I do, aside from taking the engine apart, to fix it?  Drive it hard for a bunch of miles and hope it seats?


I have just ordered the Bob's Machine catch can that others have recommended as being high quality and effective. 

Running larger diameter hoses for slowing the velocity makes good sense.

I will use that setup, with the PCV mounted at the back of the intake, going into the catch can, and then routed correctly to the front-vacuum-port spacer plate under the carb. A good quality breather on each valve cover will be also employed. 

I'll hopefully be able to get to that install within a couple of weeks, and I will post on how it's working.

Thanks again to everyone who has helped on this topic!  I think I'm better edjumacated now. 
Van

[Bob Gaines]

Here are some pictures of the historic configuration of the competition 427 done on a CSX 4000 car . In this scenario the high mounted catch can is mounted high on the firewall . Threaded inserts are in the backside of the can and it is bolted from the passenger side. Vent from intake to the can ,another down low to drain can oil buildup back to pan and the last has hose attached to vent away under the car. The cans started life as gas cans for old style mowers and other small engine applications. This is a historic type setup like used back in the day . Even though it is improbable that oil could get done the final vent tube given the configuration in a measurable amount the venting to the road would be considered a no no by todays open track rules. It would have to be routed differently . This is not meant to be a solution to your dilemma but it is meant to give ideas to possible adapt to your situation so that you don't have to have the out of character (for the car) pvc plumping/catch bottles and what not . I think a 55 year technology style car is better suited with items that don't stand out as from another era when you can help it . If you can't help it so be it . Hopefully it will give some useful ideas . Just my opinion others have theirs.

[shelbydoug]

I like that tank. That's cool. I remember those on lawnmowers! Yikes! Ebay or Craigslist? Now they're gonna' be hot!

You can probably solder one up out of copper tubing and make it look like that?


With all due respect to exactly which gizmo tank to select, it has a lot to do with which car you are working on and where you can fit it in "gracefully". I just found that vertical tanks fit better in my applications.

The Daytona Coupes had the engines lowered in the chassis about one inch. Could you do that to a BB Cobra? If you can't get the tank any higher, lower the river, I mean the engine?

[Bob Gaines]

I like that tank. That's cool. I remember those on lawnmowers! Yikes! Ebay or Craigslist? Now they're gonna' be hot!

You can probably solder one up out of copper tubing and make it look like that?


With all due respect to exactly which gizmo tank to select, it has a lot to do with which car you are working on and where you can fit it in "gracefully". I just found that vertical tanks fit better in my applications.

The Daytona Coupes had the engines lowered in the chassis about one inch. Could you do that to a BB Cobra? If you can't get the tank any higher, lower the river, I mean the engine?

Yep if you can find a tank that is how they are done . The tanks have been hard to find for a number of years now. My post was specifically addressing the Kirkham Cobra application of the OP.