PCV Catch Can

[Dutch]

I’m looking at installing a PCV catch can.

I’ve done some research and it could boost performance and keep the engine cleaner. Has anyone have any experience doing this? The reason I’m looking into his is:

After having owned my delorean for a few months now and having tried to get it running right (issues from bad wiring, vacuum leaks, ruptured fuel lines), I’ve decided to do a full engine rebuild.

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I took the dissembled engine to a local performance shop (for the Tampa Bay area I would recommend Ray's Performance Machine Shop). They hot dipped the engine to clean it, honed the piston liners, reseated the valves, and resurfaced the headers (with valuable insight from John at SpecialTAuto). As they completed the work they mentioned that my headers and block had been modified (enlarged ports, upgraded racing studs etc).

When I bought the car the PO advertised it with DMC California performance cam shafts and Special T automotive performance headers, I initially to no notice of it (I was a happy new delorean owner). However now I wanted to know more about it. After using my best friend on the net Google looking for the performance cams I discovered the following post:

http://www.projectvixen.com/dmcnews-archive/msg79587.html

Well, that’s the car I have now.

I’m still in the process of the rebuild and currently buying all new seals, gaskets, bearings, fuel lines, master slave, clutch (looking at stage III clutch from specialTauto because of the performance, does anyone have any experience) and other parts.

So when I took the engine apart I noticed that all the vacuum lines where lined and filled with smudge and oil, the rest of the components too, so there is definitely contamination. I was hoping that perhaps installing a catch can eliminate this. Below is a youtube of how and what:

https://www.youtube.com/watch?v=3KrSn3BoeLE

Also any advice on the next part, the reassembly, would be greatly appreciated.

Thanks

Dutch

[sdg3205]

Interesting.

We don't have PCV's though. Would you tap each valve cover and somewhere on the intake to create a system?

[DMC5180]

Interesting.

We don't have PCV's though. Would you tap each valve cover and somewhere on the intake to create a system?

Not the kind most people are familiar with. The oil fill cap is the PCV. That's why the hose is connected to the air cleaner.

[sdg3205]

Ah yes, of course. Does it work properly as a pcv for both cylinder banks? I have always felt the seal to be a little lacking.

[DMC5180]

Technically, yes. The oil drain passages in the head and timing chain cover area are equalized crankcase pressure areas.

the O-ring seal does seem marginal at best. I installed a new o-ring in the past and even then it wasn't what I would call seal tight. Positive Crankcase Vent just means the negative pressure created in the intake of the running engine draws positive crankcase blow by gases in the engine for recycling. There is a slight vacuum in the crank case. So maybe that's why the simple o-ring seal on the cap works.

On a piston aircraft engine the CrankCase vents to atmosphere overboard.

Dennis

[sdg3205]

I don't recall ever seeing any oil in the tube to the intake. Either the filter on the cap is really good at doing its job or the system doesn't operate like a modern pcv.

[DMC5180]

There is the other small vacuum hose that connects to the CS brass tube. On my engine it definitely has oily crankcase gases going through it. My Blue silicone hose has turned brown and seems like it oozes engine oil through the material. Probably incompatible material for the application.


Dennis

[Bitsyncmaster]

There is the other small vacuum hose that connects to the CS brass tube. On my engine it definitely has oily crankcase gases going through it. My Blue silicone hose has turned brown and seems like it oozes engine oil through the material. Probably incompatible material for the application.


Dennis

Mine does the same. I was considering not using silicone hose on that one hose. By the way, I did try to use PCV via tapping the passenger side valve cover. It ended up pulling to much oil into the intake and the exhaust would burn your eyes. So if you do a PCV, make sure you have a really good baffle to limit oil flowing.

[Dutch]

In doing some additional research if found the following post on PCV (http://dmctalk.org/archive/index.php/t-7246.html - Credits to David Teitelbaum)


According to information on this PCV system air is drawn from the air cleaner through the oil cap and then routed into the intake manifold (using its vacuum).

Although vacuum in the intake manifold is used to create a flow from the air cleaner via the oil cap to the intake manifold, it doesn't mean there's a vacuum inside the crank case.
The air flow created by the intake manifold vacuum is only used to draw (blow-by) vapors from the crank case.
If there was a vacuum inside the crank case, the vapors would stay inside the crank case.

So, there is a vacuum.

In the strictest sense the crankcase is not under vacuum. There is air flow, enough to keep the crankcase at atmospheric. Air is going in to replace the air being removed. Positive Crankcase ventilation means the air is being forced (directed) as opposed to the earlier type of ventilation, an air tube usually coming off of the highest point of the motor, generally a valve cover and any pressure being expelled to the atmosphere. In PCV that air is run through the motor so any hydrocarbons can be burned. Most manufacturers use a calibrated orifice AND a check valve to prevent any blow-back from a back-fire. The Delorean only has the calibrated orifice. Too much vacuum and you suck oil in from the valve stem seals.

In my case the contamination might have been just the whole system not taken care of. I'll look in to the vacuum hose that connects to the CS brass tube and see what goes on there.

Again any suggestions, advice I can get on the rebuild would be appreciated.

[dn010]

My original engine had 70K+ miles on it and did not have any kind of deposits or build up/sludge, however as mentioned; my once blue silicone hose changed color due to residue and that is about all. You are more than likely correct in that the poorly maintained system caused your issues, I'm sure vacuum leaks diminish the amount of air being pulled from the crankcase which would lead to sludge.




In my case the contamination might have been just the whole system not taken care of. I'll look in to the vacuum hose that connects to the CS brass tube and see what goes on there.

[Tomcio]

Let me chime in on this subject...
Intake vacuum draws air through the air filter and that black hose going to the oil filler cap. In effect there should be a little bit of vacuum in the crankcase unless there are holes to the outside allowing air to enter. Another source of too much air (or gas) in the crankcase is the ring blow-by.
In the first case (a hole allowing air to enter the crankcase) you would probably see oil leaking in that area. This includes valve cover seals, timing chain cover seals or any other oil passage with no positive oil pressure. A leaking oil pressure sender will not allow air to enter the crankcase. If you do not see any oil on the outside of the engine in those areas but there is a lot of oil in the intake I would check cylinder compression. That might indicate excessive piston ring blow-by which creates too much positive pressure in the crankcase pushing too much oil into the intake manifold. A dry compression test first, then again after adding a bit of oil into each cylinder. I would expect to see a jump in compression indicating worn rings. A cylinder leak-down test might also be useful here.
In many cases this is a good indication of a worn engine.
A catch can is useful on turbo engines because a turbo creates higher cylinder pressures and higher ring blow-by in effect pushing the oil out of the engine.

In a well maintained naturally aspirated engine there is no need for a catch can. If you need one, you need to address the issue causing the excessive crankcase pressure first. Adding a can will not fix the problem... it's like putting a band aid on a broken arm.

[Dutch]

Hi Tomcio, I concur with what your saying. Because I'm doing a complete rebuild I can see what's going on in the engine. As I mentioned I did the teardown for a reason, bad performance, leaking etc. I'm expecting a clean and lean engine after completion without leaks of any kind (oil , vacuum).

I started the topic to see if anyone had tried it and or had the same issues I had. Thanks for your insight.


Sent from my iPhone using Tapatalk

[Tomcio]

No problem, glad I could help ;)
If you're doing a full rebuild (guessing from the picture in the original post it is a COMPLETE job) then you don't have to worry about a catch can. If the rebuilt is done correctly the can will just stay empty. There are some gasses from the blow-by that cause some yellowy-brown film on the intake but that is mostly gas and some very fine mist. All that should be burned inside the cylinders. Save some money by not buying the catch can ;)

BTW, it's so nice to see people from all those familiar places... Tampa and Pinellas county. I used to live in Clearwater.

Good luck with the rebuild! You can use my car as a benchmark because from what I can see I'm lucky to have one of the best PRVs out there. My car (before I started a ground up restoration) was running 0-60 in 8.0 seconds pretty much every time. With the mods that you have and a freshly rebuilt engine you should easily beat that.
My engine is 100% stock, manual transmission.

Tom

[Delorean Industries]

We have proven through extensive dyno testing that the factory crank case ventilation system does not properly function at sub 100 kpa levels let alone under boost. This is why every island/bae car in existence pushes seals at sub 130kpa. At the very least venting is required in both valve covers independently of each other with basic breathers on naturally aspirated applications. On forced induction applications a secondary scavenging system is required with a one way recirculation valved return line into the lower case. (valve orientation allows for scavenging pump to pull oil back into case but is over come and closes if crank case pressure exceeds scavenging pump cfm.)