Catch Can with or without PCV? Which is best?

[Side-Oilers]

My Kirkham 427, with a fresh aluminum 482 engine, is getting a bit of blow-by on the passenger side during deceleration, from approx 3000 rpm and up.   The engine is great other than that.

I installed an M/E Wagner adjustable PCV, connected to passenger side valve cover, and to a vacuum port under the carb.  I tuned it for the optimum vacuum, etc.

The other valve cover has a period-style Ford breather.

I'm now thinking I need a catch can.   So, is it better to run a closed system that retains the PCV, or an open system with no PCV, and vent(s) on the catch can?

I've read that the vented can scenario is the race car type (not really necessary on my street driven Kirkham) and will emit a fuel or oil vapor when the car is idling, like at a traffic light.

I'd appreciate anyone's thoughts, opinions, best plumbing ideas, recommended hose sizes, and anything else. 

[s2ms]

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.

[shelbydoug]

My Kirkham 427, with a fresh aluminum 482 engine, is getting a bit of blow-by on the passenger side during deceleration, from approx 3000 rpm and up.   The engine is great other than that.

I installed an M/E Wagner adjustable PCV, connected to passenger side valve cover, and to a vacuum port under the carb.  I tuned it for the optimum vacuum, etc.

The other valve cover has a period-style Ford breather.

I'm now thinking I need a catch can.   So, is it better to run a closed system that retains the PCV, or an open system with no PCV, and vent(s) on the catch can?

I've read that the vented can scenario is the race car type (not really necessary on my street driven Kirkham) and will emit a fuel or oil vapor when the car is idling, like at a traffic light.

I'd appreciate anyone's thoughts, opinions, best plumbing ideas, recommended hose sizes, and anything else. 

I am running this setup and it's my opinion (sometimes I even argue with myself though) that it is more of a skimmer then anything and is only going to have a percentage of effectiveness.

I find very little oil in my "catch can", mostly an inch or two of water.

So really, it's anyones guess how well it really works?


Maybe look for a catch can from a current tight emissions car and see if there is internal switching on them.

Thinking about it, I think there is an electrical connection to the one on my Audi and I need to investigate why.

They are most likely on the car to protect the cat from further contamination from oil deposits?


Good question but I don't know the answer to your question. Just speculation since I'm only as far along as you are.

[shelbydoug]

I found that the best setting on the Wagner is using the under 10 inch method. It completely shuts off the valve at idle and results in higher idle vacuum.

I went from 12 inches to 16-17 inches at idle on the same 236@.050 cam. That's all in the pcv system. I'm very happy about that.

That was basically just changing the spring in the Wagner valve.


I don't think that you need an open breather in the valve cover. The air cleaner is essentially functioning that way already. Take off the top of the aircleaner while the engine is idling. Look at the water vapor coming out of the connection. That thing is open already.

Try closing up the open valve cover. See what the results of that are? If you really want to be scientific, you could hook up a vacuum gauge somehow to the pcv system. You don't want more then about 12inches otherwise you'll suck in things like the crank seals which I would predict to be a bad thing.

The header scavaging system provides something like only 6 inches but most racers use it these days, but talk about sucking oil out of the covers and making a mess? That's it.

The suction point is too low and will encourage siphoning oil out of the valve covers.

[pbf777]

.................... a bit of blow-by on the passenger side during deceleration, from approx 3000 rpm and up. 

      I gather with your concerns of valve cover attachments that your reference of "blow-by" is as observed from the valve cover breather?  Not from the tail pipe?     

I installed an M/E Wagner adjustable PCV, ....................................  I tuned it for the optimum vacuum, etc.

     "Optimum vacuum"?  A control setting for the implied "ideal" operation?  Really!  And how is this "ideal" actually going to be established "in-the-field" and with which parameters for observed function or result?   

       Now I'm aware of perhaps (depends on the application) an observed loss in the vacuum value (change in manifold pressure) within the induction system when a P.C.V. valve is instituted, and a at times real concern for this effect (particularly on a carburetor) but?           

       In my opinion this is a perfect example of creating an implied need, then with a product (gadget) to solve no real issue, but in the price range that will lead to many a "what-if' or "why-not" sale!  But it is a cool billet gizmo anyway!   

      Scott.
     

[shelbydoug]

.................... a bit of blow-by on the passenger side during deceleration, from approx 3000 rpm and up. 

      I gather with your concerns of valve cover attachments that your reference of "blow-by" is as observed from the valve cover breather?  Not from the tail pipe?     

I installed an M/E Wagner adjustable PCV, ....................................  I tuned it for the optimum vacuum, etc.

     "Optimum vacuum"?  A control setting for the implied "ideal" operation?  Really!  And how is this "ideal" actually going to be established "in-the-field" and with which parameters for observed function or result?   

       Now I'm aware of perhaps (depends on the application) an observed loss in the vacuum value (change in manifold pressure) within the induction system when a P.C.V. valve is instituted, and a at times real concern for this effect (particularly on a carburetor) but?           

       In my opinion this is a perfect example of creating an implied need, then with a product (gadget) to solve no real issue, but in the price range that will lead to many a "what-if' or "why-not" sale!  But it is a cool billet gizmo anyway!   

      Scott.
   

Not to defend the indefensible but in my case I wanted a pcv that fully closed at idle.

That is the identified issue. The Wagner was the selected solution.


It wasn't as large an issue with the 2-4's but the IR with the Webers on the Cleveland was only giving me 11-12 inches.

Could I have run open breathers and have them dripping all over the valve covers and running on the headers? Sure. How is that a solution?

I could cook a pizza on top of the hot engine too but I don't see that as successful or desirable multitasking and in addition, the dripping valve cover vents would ruin the pizza.

I wouldn't even do that to a TVR. 


The Wagner isn't just a pretty face gizmo, it's a highly engineered gizmo. How do you know you need it? How do you know you need 1,000hp?


If you want to run a car on a track these days a catch can is required for the pcv AND the radiator overflow, so it isn't exactly a solution searching for a problem.

[s2ms]

I am running this setup and it's my opinion (sometimes I even argue with myself though) that it is more of a skimmer then anything and is only going to have a percentage of effectiveness.

I find very little oil in my "catch can", mostly an inch or two of water.

So really, it's anyones guess how well it really works?

Yes, how well it works is the big question. FWIW, I recall reading That Ford Performance uses the Bob's Machine separator on the GT350 Track Attack cars.

I haven't tried the Wagner valve but did talk with the one of the owner's about my situation, super nice and helpful guy. Ended up not getting it because my situation looks under control with the new baffle. I believe what little oil is still getting into the can is due to my Lunati cam as well, ~11 in at idle, 239@.050, I bet the Wagner would clean that up using the under 10 inch method. Looks like a solid product, IMO if you can measure the difference in oil collection it's at least a gizmo that works as intended.

When I first started to evaluate how well the new PCV baffle design was working, I was using 2 of the cheapo Steeda cans in parallel, seen in the pic below, to measure oil collection. The first can always had ~2x more oil than the second. The Bob's Machine can picks up more than both of the Steeda cans together.

[shelbydoug]

At the risk of repeating myself, repeating myself, my issue with every Ford small block I've owned is that the "factory" pcv system ALWAYS siphoned oil out of the valve covers and into the intake manifold. Always.

Now take that, the requirement of a track catch can and looking for more idle vacuum for the brakes without a vacuum pump, this all got mixed into an attempt at a COMBINED SOLUTION.


After seemingly going through every pcv  part number conceivable, the Wagner became a logical and economical solution.

I eventually stopped blaming China for poor quality pcv's and realized that by design, NONE completely closed at idle. Not even the L88 version with that lumpy factory idle.

What I DISCOVERED with the Wagner is that if I followed instructions the darn thing didn't completely close at idle but "discovered" by chance, if I changed the spring to the 10 and under instructions, all of a sudden it did, and I had mega vacuum available.


So that's my story and I'm sticking to it and yes, don't even ask the question, at times I do think I'm delusional? My oldest son is the kindest. He just says, "you have too many parameters open at the same time. How can you possibly understand what is going on at any one moment". Bless him!

[s2ms]

At the risk of repeating myself, repeating myself, my issue with every Ford small block I've owned is that the "factory" pcv system ALWAYS siphoned oil out of the valve covers and into the intake manifold. Always.

And......the Cobra intake design makes matters worse since that PCV system dumps directly into the intake right next to cylinder #4, so it get's hammered.

At least that should not be an issue with the OP's concern since his system is connected to a vacuum port under the carb, the PCV siphoned oil should be distributed more or less evenly between all cylinders, in theory anyway.

[shelbydoug]

At the risk of repeating myself, repeating myself, my issue with every Ford small block I've owned is that the "factory" pcv system ALWAYS siphoned oil out of the valve covers and into the intake manifold. Always.

And......the Cobra intake design makes matters worse since that PCV system dumps directly into the intake right next to cylinder #4, so it get's hammered.

At least that should not be an issue with the OP's concern since his system is connected to a vacuum port under the carb, the PCV siphoned oil should be distributed more or less evenly between all cylinders, in theory anyway.

Well I think that the height of the intake port is significant. The higher it is the less it SHOULD siphon.

I think of two exceptions to that thought or maybe where that just didn't matter.


My 68 302 had a spacer under the carb to give the pcv a higher connection. No dice. Sucked it in.

Parents 76 302 Granada. Same type of spacer under the carb. Sucked the pan dry (under waranty).


A side thought here as well. There are people that will argue on the small block, the FE and the Cleveland, that there were significant bottom end failures due to lack of oil.
They blame everything under the sun for them. NONE of them take into consideration this major fault of siphoning oil.

[Side-Oilers]

Thanks one and all...

My M/E Wagner is set up for 8-inches of vacuum at idle, and about 10 at 2000 rpm. 

Here's a pix of my setup.   I was still running the back of block vent then. I now have it capped off.  Also, this pix is before the carb base plate was installed.

Doug, as you mentioned...is the carb base plate where the PCV hose is connected my biggest problen?

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.)

[SFM5S000]

Well here's my venting setup. Because I run Weber's, I have no provisions for a PCV. My only option or should I say the direction I took was to run twin breathers plumbed to a vented Catch Can. The can was mounted without drilling a single hole.
Here's a birds eye view which can be easily duplicated in a cobra engine bay regardless of induction system.

Cheers,
~Earl J

[shelbydoug]

Thanks one and all...

My M/E Wagner is set up for 8-inches of vacuum at idle, and about 10 at 2000 rpm. 

Here's a pix of my setup.   I was still running the back of block vent then. I now have it capped off.  Also, this pix is before the carb base plate was installed.

Doug, as you mentioned...is the carb base plate where the PCV hose is connected my biggest problen?

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.)

If you ask me after describing the symptoms that you are concerned about, I think that spacer connection is as the "Ghost Busters" might say, "is spook central". LOOK at the way the hose drops down below the oil level in the valve covers with the engine running. That's siphoning oil right there. That hose needs to be elevated.

You can see, even with Earl's post, that we are all dealing with similar situations.


I explained my observations of what my catch cans are doing. I can tell you that on my Audi TT, the catch can to that group is a PITA and is doing the same thing of largely collecting water and some oil droplets. However, the thing is connected differently away from the valve cover possibility of siphoning out oil.


Earl. What started this therapy session for me (working out these types of issues is therapy to me although I just heard a new term referring to me. What does "Bat s hit" mean? Is that good?)


Here's the pictures of my Pantera system. You can see the vacuum plumbing but the collector of those tubes is a fuel log under the heat shielding. More importantly, look at the catch can, plumbed to the valve cover and that runs to the "vacuum log".

I relocated the pcv port into the valve cover also as you might notice?


So here is a IR Weber system with a pcv, so don't say you can't do it.

Webers dump a lot of fuel because of this, "let's mash the throttle" mania that comes over you just because you can.

That eventually does a job on the top compression ring because of the cylinder washing. IF EVER there was an engine that would welcome more piston ring sealing BECAUSE of a pcv system, it's a Weber system like this?

Does it actually work? Maybe?

OH LOOK, you have one just like it? Small world?


These pics are mostly for Earl. You can plumb the Webers for vacuum and then add pcv to that system.
If you don't want to drill the intake, fabricate spacers for under the carbs that you can add a vacuum port to.
Necessity is the mother of invention. 

[pbf777]

Not to defend the indefensible but in my case I wanted a pcv that fully closed at idle.

Could I have run open breathers and have them dripping all over the valve covers and running on the headers? Sure. How is that a solution?

     Often even the most incapable function will find usefulness, somewhere, somehow, and prove a capable, usefully ally!  But I am attempting to reference the most commonly encountered scenarios one can expect to encounter.

    And I perhaps understand your intention wishing to have the vacuum loss to the P.V.C. system defeated at idle, this apparently to aid in carburetor function (a concern mentioned previously), or perhaps just for better vac. booster effect but what is it that you expect from the P.V.C. system at higher engine speeds?

    Oil carry-over control from the valve covers(s) or other orifice openings from the crankcase to atmosphere are not in the realm of responsibility of the P.C.V. system though some arbitrary value is had particularly at idle (I guess not in your case though) and perhaps low engine revolutions, but as this system has limited flow capacity and the by-pass sums from particularly combustion pressures quickly increase with load and R.P.M.'s this does outstrip this potential possibility.

If you want to run a car on a track these days a catch can is required for the pcv AND the radiator overflow, so it isn't exactly a solution searching for a problem.

    Why would and what would a "catch-can" requirement do in the P.V.C. plumbing circuit as this system amounts to a sealed pathway from crankcase access (valve cover is common to American V8's) to that of the low pressure manifold area meaning that nothing is going to be escaping or leaking on the ground (the concern for "catching the oil), but rather any oil carry-over is going to routed thru the combustion process leading to only fume out the tail pipe?  On the opposite valve cover of the typical "closed crankcase system" (again as is common to American V8's) again a sealed plumbing pathway is provided from the air cleaner canister to the crankcase area for the purpose of first presenting an atmospheric source for the P.V.C. system to ultimately access as this is drawn thru the crankcase and secondly where when the blow-by (or some prefer "blow-down") sum becomes to great for the P.V.C. plumbing to handle, there will be a reversal in flow direction with the excess volume is then vented to the, again lower than atmospheric pressure, air cleaner canister to be still ingested by the engines' combustion process and out the tail pipe.  This presenting a "closed crankcase ventilation system", what's to "catch"?       

     Now the engine may present whether with or without the presents of a P.V.C. valve, an "open" (to atmosphere) crankcase breathing access, now this does obviously require a "catch-can" and so may some rulings from some race organizations on the prior "closed system", but I am just posing the statement for thought of.........WHY?       


     And also realize that it is not the purpose or intention to actually utilize the P.V.C. system to create a vacuum sum on the crankcase area or as a substitution for the intention of say a dedicated crankcase vacuum pump.     

I wouldn't even do that to a TVR. 

     Does this statement qualify as automotive racism?   I think I'm offended!     

     Scott.

[s2ms]

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