1. Registration trouble? Please use the "Contact Us" link at the bottom right corner of the page and your issue will be resolved.
    Dismiss Notice

Pcv System, Oil Catch Can, Anyone Build One?

Discussion in 'Early CJ-5 and CJ-6 Tech' started by 70cj5134f, Jan 12, 2019.

  1. Jan 12, 2019
    70cj5134f

    70cj5134f Member

    East Tn
    Joined:
    Aug 18, 2018
    Messages:
    441
    This 3.7 engine is prone to detonation, I'm trying to eliminate all I can.
    I noticed some oil in pcv line, oil in intake mixes with fuel and raises octane requirements.
    I'd like to run pump fuel. After research I found a correctly installed catch can would
    Eliminate most of the oil. Anyone build their own, or use a store bought one?
    Ideas?
    Opinions?
     
  2. Jan 12, 2019
    timgr

    timgr Jeepin' Nerd Sponsor

    Medford Mass USA
    Joined:
    Aug 10, 2003
    Messages:
    19,232
  3. Jan 12, 2019
    Keys5a

    Keys5a Sponsor Sponsor

    Joined:
    Jan 23, 2014
    Messages:
    1,769
    As I recall, didn't you have the head or block milled, altering the quench area and compression ratio? These engines don't usually have detonation issues. In a boat, the load on the engine is similar to a car always climbing a long grade. You might try taking a little timing out of it, or 93 octane. I doubt a slight amount of oil vapor is enough to be causing the detonation.
    -Donny
     
  4. Jan 12, 2019
    Jw60

    Jw60 Midwest traveler

    Sedalia MO.
    Joined:
    Oct 5, 2018
    Messages:
    55
    I feel your pain, this is part of why I had to go v6 instead of turbo. You can Baffle the inside of the engine cover the where pcv line connects to the head or crankcase so anything caught there drains back internally. then you can make a catch can like Tim describes by having the vent hose enter a container filled with metal scrubbies (non soapy) basically making a small f134 oil bath so the oil changes direction so much it contacts the metal and escapes the airflow via surface tension and gravity, then for icing on the cake make a drain from this vessel to the crank case. This is the same concept used in overhead kitchen hoods to prevent grease fires. (Google Burger King exhaust fire)
     
    Last edited: Jan 12, 2019
  5. Jan 12, 2019
    Cap-n-Cray

    Cap-n-Cray I want to do this again.. Staff Member Sponsor

    Bainbridge...
    Joined:
    Sep 21, 2009
    Messages:
    202,256
    Not sure about your engine, but my 01 Ram diesel has a small bottle with some 3/8" holes around the top. It collects blow by oil. I empty it every oil change. Never gets that much oil and it's simple...
     
  6. Jan 12, 2019
    70cj5134f

    70cj5134f Member

    East Tn
    Joined:
    Aug 18, 2018
    Messages:
    441
    Had the block milled to tighten quench for less det. But i could hear #4 ratteling(its next to the vac hose that sucks the pcv system i hooked up), removed pvc hooked the valve cov vent back to breather and it stopped! But its leaner, and revved better, when pcv was hooked up!
    That's why the oil separater. It likes more timing than I'm givinging it.
    Set on 8btdc (book specs). But it runs better at 10-12btdc.
    Read so many post on det and blowing gasket that I'm trying to fix before they bite!
    I'd like to run 89, but 91-93 pump would be ok!
    Ps-any idea on what temp fan switch I need?
    Plan on running a 160 stat.(No heater).
    I'm thinking 185 on would work?
     
  7. Jan 12, 2019
    70cj5134f

    70cj5134f Member

    East Tn
    Joined:
    Aug 18, 2018
    Messages:
    441
    My homemade test catch can.
    More later.
     

    Attached Files:

  8. Jan 12, 2019
    Oldriginal86

    Oldriginal86 Member

    Pasadena, Md.
    Joined:
    Nov 5, 2014
    Messages:
    379
    I would make the one hose end inside the can long enough to almost reach the bottom. That way the vapors would be drawn up through the mesh.
     
    70cj5134f likes this.
  9. Jan 12, 2019
    scott milliner

    scott milliner Master Fabricator

    Seattle Wa.
    Joined:
    Dec 17, 2002
    Messages:
    1,882
    Why make one. Have you seen how cheap they are on Amazon?
    I had one on my 2014 LS3 Chevy V-8. That motor had a lot of oil that would pump through it that would make it into the intake.
    I also have one on my 4 cylinder turbo diesel to keep oil out of the turbo and intercooler. This one I don't see as much.
     
  10. Jan 13, 2019
    70cj5134f

    70cj5134f Member

    East Tn
    Joined:
    Aug 18, 2018
    Messages:
    441
    I did just that only more. I caped the end so it wouldn't suck oil from bottom, drilled
    A bunch of 1/8 holes in tube, and built a wall almost touching the bottom so the air
    Had to travel down then back up through the steel wool. I saw this design on another
    site. Pics later.
     
  11. Jan 13, 2019
    70cj5134f

    70cj5134f Member

    East Tn
    Joined:
    Aug 18, 2018
    Messages:
    441
    25Hg vac, vs, qt thinner can.
    Idled fine, pcv barley letting any vac through!
    1st rev, I heard a pop? 1 side of can shrunk in!
    2nd rev, way higher rpm, slam shut, then the can shrunk to what u c heer.
    Good design, wrong materials.
    2nd can already in fab.
    Old paint gun cup and lid.
    Tapped center hole to 1/8 pipe thread.
    Drilling 1 hole in lid for line to valve cover, I'll use center for pcv to intake manifold side.
    I'll cap end and drill small holes in tube.
    15474030172361902961022.jpg 1547403070529588945178.jpg
     
  12. Jan 13, 2019
    Berserk71

    Berserk71 New Member

    Joined:
    Jul 29, 2011
    Messages:
    3
    PCV valves are designed to allow for a certain amount of vacuum leak at idle and cruise. Engines can only idle correctly with a certain amount of vacuum leak. anything more than that and it will cause idle problems that will also affect timing at idle. Cruise can afford slightly more so the PCV valve opens more to evacuate more crank case vapors. A stock PCV valve will work fine on a stock engine but when you start modifying the engine the acceptable vacuum leak at idle and cruise may change and therefor the stock PCV valve will not work properly. I purchased an M/E Wagner adjustable PCV valve, experimented with it, and now I am convinced that it is a must for any modified engine. They are expensive but well worth it, IMO. I run the PCV from the top of a catch can, of which I am a believer in, instead of the valve cover, so it doesn't get fould up. It's machined aluminum with tight tolerances, also rebuildable. I've also noticed that the catch can removes incombustibles from the intake making the A/F mix burn better and improves idle. I also like to run as much advance at idle as possible, with vacuum advance can attached. Keeps it much cooler at idle. Also, you should have your vacuum advance connected to full manifold vacuum like it was originally designed for. Some people insist it should go to ported vacuum like they came from the factory but that was done only as a way to cheat emission tests at the cost of proper idle. Lot's of overheating vehicles in the 70's in traffic.

    The steel wool catch can version has always concerned me because the strands can come loose and get sucked into the engine. Currently my can is empty. It still works, maybe not as well as it could but until I can figure a better way it works well enough for now. It's primary purpose is to keep the PCV clean.
     
    70cj5134f likes this.
  13. Jan 13, 2019
    70cj5134f

    70cj5134f Member

    East Tn
    Joined:
    Aug 18, 2018
    Messages:
    441
    No vac adv, mechanical only.
    I was thinking of a filter In the manifold vac line?
    Thanks! 15474219055131287984945.jpg plan B, this won't collapse. Vac through tube small holes, down under wall, through wool,
    gravity should keep most at bottom?
    Similar to design I found on web!
     

Share This Page

New Posts