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Thread: Tri-carb PCV valve

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    Jedi Warrior Drone Dog's Avatar
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    Tri-carb PCV valve

    was thinking of trying to add a PCV valve to my Tri-carb. when i was building the engine it seemed people were having trouble finding one that would work properly. since then i believe i read an article somewhere that said they were using a PCV valve and it helped with the oil leaks.

    my questions:

    1) will adding a pcv valve help stop oil leaks. the only one i seem to have at the moment is the rear main seal.
    2) which PCV valve should i use? part number / brand?
    3) i assume i would need manifold vacuum to connect to. on my tri-carb there is a 1/4" inch plug i could use on the front instake manifold. see pic...
    fullsizeoutput_2b8.jpg

    4) anything else i should know about the install? thinking the other end of the connection would go to the valve cover vent tube.

    Thanks

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    Re: Tri-carb PCV valve

    DD - there's a lot of discussion of PCVs in previous threads.

    British Car Specialists': Norm Nock's AH book has an article on adding a PCV and a part number.
    Steve Gerow
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    Re: Tri-carb PCV valve

    Quote Originally Posted by Drone Dog View Post
    my questions:

    1) will adding a pcv valve help stop oil leaks. the only one i seem to have at the moment is the rear main seal.
    2) which PCV valve should i use? part number / brand?
    3) i assume i would need manifold vacuum to connect to. on my tri-carb there is a 1/4" inch plug i could use on the front instake manifold. see pic...
    fullsizeoutput_2b8.jpg

    4) anything else i should know about the install? thinking the other end of the connection would go to the valve cover vent tube.

    Thanks
    I ran a PCV valve for years per Norman Nock's instructions. Two years ago, I had the engine overhauled by an excellent builder; I was going to have him install a rear main seal--which I already had--but he insisted I stick with the PCV valve, but had a better idea for the installation:

    IMG_0418.jpg

    Previously, the PCV installation had reduced dripping from the bell housing and cut oil loss from 1qt/1K miles to about 1qt/2K miles (which is pretty good for a Big Healey). The overhauled engine still uses some oil, but with the new PCV installation I have not had one drop come out of the bell housing. YMMV.

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    Re: Tri-carb PCV valve

    Quote Originally Posted by steveg View Post
    DD - there's a lot of discussion of PCVs in previous threads.

    British Car Specialists': Norm Nock's AH book has an article on adding a PCV and a part number.
    Yep !

    I tried them on my BJ8 upside down crosswise N Crooked when Norman published the article but for me they would not work others have had good results though.

    Yes BOB:

    If it works correctly it will reduce crankcase pressure and the related oil leaks.
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    Re: Tri-carb PCV valve

    I was running one for several years. I have a BJ8 manifold with a pair of HD8 carbs. The vacuum connection I used was the one that would have been used for the brake booster. It is near the rear carb. I took off the intake manifold and headers to replace the manifold gasket. When I looked at the top of the intake valves, 1 through 4 were clean, but 5 and 6 had hard, black deposits on them from oil vapor that had been cooked onto the valves. That's when I decided to let the engine leak and keep rust off the frame.
    John, BN4

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    Re: Tri-carb PCV valve

    steve
    i tend to ask questions here first and then start to search. Maybe not the best way to do it.... but i do. partly because i have such limited success with the searches. and partly because when i do find something it is old and i wonder if the thought process has changed since then.

    i did find some older threads on this site and have been reading thru them.

    i don't have Norm Nocks AH book and i could not find any info on the BCS website. (again probably me)

    Bob
    it looks like you have balanced your system to include both sides of the intake. not something i am ready to do at this point. wondered about that being an issue, extra air at that intake (lean condition) and extra oil to the intake valves.

    i put the rear main seal kit on my engine during the rebuild but i know it is still leaking oil. i made a small catch pan that bolts to the bottom two bolts of the bellhousing. little over an inch tall. made from the bottom of a metal gas can. i keep a paper towel in there to catch the oil and then just change every so often. i don't get any oil drips from there on the floor. but i wondered about getting oil on my clutch.

    was hoping this PCV setup could let me get rid of the catch pan.

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    Re: Tri-carb PCV valve

    DD - I couldn't find NN's book on their site, either. One might have to give them a call. Maybe they make them to order. It's a valuable knowledgebase and great rainy-day reading.

    Anyway, he advocates the PCV between the "T" on the valve cover and the vacuum port to the rear of the rear carb.

    John Tunney's results argue for a balanced vacuum per Bob Spidell's setup.

    IMO the actual PCV used isn't that important. You want one for a medium-sized 150 HP engine.

    On a tri-carb, maybe the best bet would be to pull from the balance pipe midway between each set of cylinders.
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    Re: Tri-carb PCV valve

    I expected my rear cylinders to be gunked-up but, surprisingly, they weren't bad. I think a catch can would be a good idea if you could find a way to rig one between the PCV valve and the manifold.

    Cyl Head.jpg

    I just ordered a catch can for my Mustang's 5L engine; apparently, these things emit a lot of blowby and the intake system can get gunked-up.

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    Re: Tri-carb PCV valve

    Hi All,

    Bob, which PCV are you using? If I remember correctly, I think the PCV recomented by Norm was an AMC Concord 6-clinder which is difficult to get now. Are you sharing the manifold port for the brake booster with the PCV or have you made a separate connection for the PCV? Do you notice any differences in brake booster operating assist?

    Since I did create a oil vapor catch can for the PCV connection but didn't install a permanent PCV, I kept the catch can and just installed it between the "T" and the carburetor air cleaner.

    Figure 2.jpg Figure 9.jpg

    Ray(64BJ8P1)

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    Re: Tri-carb PCV valve

    Hi Ray,

    Sorry, I don't recall which PCV valve I used; it was in a kit I bought from the Nocks many moons ago. It could be the AMC valve, but I think any comparable six-cylinder-sized valve would work. I think the most important part is to get a valve with fittings that fit the hoses. I originally had to 'step down' the hose from the T-fitting but my builder found a better solution. I think David Nock would be happy to suggest an appropriate PCV valve. The kit had the valve and a small gasket to put on the dipstick flange; they recommended soldering the vent hole in the oil filler cap shut (I used a small sheet metal screw to plug it). I think the idea is to seal up the engine so that unfiltered air doesn't get in but, of course, the idea was also to suck air in at the rear main bearing thus preventing oil from seeking freedom.

    We put the rear seal on our BN2 and, perhaps ironically, there seems to be excessive pressure in the crankcase as felt at the oil filler. I'm left to wonder if the seal didn't cause that, and that engine leaks in the usual fashion. It has excellent compression--160+ on all four--so I don't think it's from excessive blow-by.

    Your catch can install is very clean. In all the PCV/catch can installations I've seen the can goes downstream from the PCV valve.

    Bob

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    Re: Tri-carb PCV valve

    Quote Originally Posted by Drone Dog View Post
    i don't have Norm Nocks AH book and i could not find any info on the BCS website. (again probably me)
    Go to the "Healey Rare Parts" in the header of their website. click on "Books" then "Technical".

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    Re: Tri-carb PCV valve

    Hi Bob,

    In all the PCV/catch can installations I've seen the can goes downstream from the PCV valve.
    The vacuum is comming from the intake manifold and pulling the noxious mix from the hoses comming form the sump and valve cover. As I understand, the catch can should be installed to extract the oily mixture from the stream before it is pulled through the PCV and taken into the manifold. Am I correct, have I missed something, or is that what you mean by down streem?

    Ray(64BJ8P1)

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    Re: Tri-carb PCV valve

    Quote Originally Posted by RAC68 View Post
    Hi Bob,

    The vacuum is comming from the intake manifold and pulling the noxious mix from the hoses comming form the sump and valve cover. As I understand, the catch can should be installed to extract the oily mixture from the stream before it is pulled through the PCV and taken into the manifold. Am I correct, have I missed something, or is that what you mean by down streem?
    Makes sense to me, IFF you have the option of installing the PCV valve wherever you like. Most modern cars have a complete PCV system, with filtered air on one end and the valve on the other (on 'Vee' engines the intake is on one head's valve cover and the valve is on the other). Here is the can I ordered for my Coyote engine:

    https://www.americanmuscle.com/jlt-v...ipping+Confirm

    Come to think of it, since you have the option, putting the valve after the can makes sense, as it could keep the valve from gunking-up (they're supposed to be replaced routinely, like every 'tune-up' but I've never done anything but make sure they aren't stuck and clean them out if necessary). The only downside I can think of is more complex plumbing and maybe the can could get plugged.

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    Re: Tri-carb PCV valve

    i have been reading this thread along with a few others and decided why not give this a try....

    factors for my decision:
    i am not likely to drive this car over a thousand miles a year makes me think the chances of coating the valves to the point of being a problem, not likely. plus it is a cheap experiment and too cold to play golf today.

    So i looked thru the info in different threads and looked at different ways people did this. i have a tri-carb so the fitting is not at the rear like a lot of others. my first thought was to run a "T" in the hose going from the valve cover to the carb. plug the carb side of the T and then run the valve / hose under the carbs to the front intake. figured this way made the least "looking" changes to the stock look. decided aginst that after not finding any fitting set up i liked at the front intake.

    So i went with a brass/copper connection to run back to the PCV and then got a PCV with a 90* elbow on it. hey adding brass and copper to an engine is always a good look right? What could go wrong?

    the PCV valve was my biggest hurtle. i did not have any idea which one to pick. No one around here has the PV770. trying to get a cross reference or any info at an auto parts store...HA! But then i couldn't find anything on line either. So in the end i just picked one i knew i could change out to the PV770 if this one did not work as planned. plus it was the cheapest one on the shelf.

    So here is what i came up with:
    i went with the hole under the plug. See picture above. i was concerned about the ID size but after looking at the PVC valve, the ID's for the valve and the 1/8" fitting were about the same. from there i transitioned from a 1/8" nipple to 1/4 FIP to 3/8" compression fitting. bought a short piece of copper 3/8" OD tubing and ran it back to the PVC. Let the 90 run over to the valve cover hose. all in i think it looks pretty clean. the one issue i thought i might have it the copper tubing bouncing around. i was going to make a bracket for the rear but ended up just using a wiring "P" clip and bolting it to the bracket which holds the fuel line. this layout used the least fittings at the intake.
    fullsizeoutput_2c0.jpgfullsizeoutput_2ba.jpgfullsizeoutput_2c2.jpg
    after the install, i made a seal for the dipstick and put a screw in the vent hole on the oil filler cap. then i adjusted the front carb mixture nut down one flat. i think that is about .006 drop on the seat.

    Next comes testing it out. a little cold today but hope to do it this week.

    testing:
    i planned to start the engine with the oil cap loose just in case it has positive pressure. sound right or not?
    second, if i read all this correctly, at idle i should have very little if any vacuum at the oil filler cap.
    third, as i increase rpm, i should feel more vacuum at the oil filler cap.

    does all this sound right? anything else i should look for?

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    Re: Tri-carb PCV valve

    Nice clean installation. Can't go wrong with your idea of starting with the filler cap loose.
    Steve Gerow
    Altadena, CA, USA
    Maker of most complete Big Healey rear disc kit
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    Re: Tri-carb PCV valve

    Hi Drone Dog,

    Very nice straight forward and visually contributing installation.

    When is manifold vacuum at its highest in a driven engine? If I remember correctly, it is during deceleration. Now consider the amount of oil vapor you will be pulling into your manifold. Even in a newly rebuilt engine, noxious oil vapor will be quite substantial in a hot running engine ... especially on a summer run. Passing that mix through your manifold could create a sludge around your valves on cool-down and cause problems.

    To eliminate that possibility, I would construct and install a simple oil catch can between the tube coming from the "T" fitting on the valve cover and your copper pipe to reduce, if not eliminate, any heavy oil that may be drawn in. The mounting should be convenient to allow for easy access to manual eliminate any collected oils condensation either through a valved drain tube or by removal and opening.

    I appreciate that a catch can is not needed on a modern car designed with a PCV, but then, the engines and PCVs were designed and tested together and you will be doing some experimentation on a newly rebuilt engine. Since most Healey owners who have ventured into the use of a PCV have eliminated them over time for various reasons, cider the catch can installation a precautionary action with its possible elimination after all proves good.

    Just my thoughts,
    Ray(64BJ8P1)

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    Re: Tri-carb PCV valve

    Ray
    thought has crossed my mind. been looking at some catch cans on line. first i want to make sure it works properly. then see how i could mount a can that would not be in the way.

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    Re: Tri-carb PCV valve

    re: "I appreciate that a catch can is not needed on a modern car designed with a PCV."

    Not necessarily; many modern cars are going to Direct Injection for efficiency. With Gas DI (GDI), the intake ports and valve backsides don't get 'washed' with all the wonderful cleaners the gas companies advertise, and carbon (gunk) buildup in those areas is apparently a real problem. My Mustang has both GDI and port injection so, presumably, the ports and valves get some cleaning, but owners of Coyote engines that have installed catch cans report a teaspoon or two of oil in the can over a few thousand miles. And, spaying Techron, or whatever, on the intake ports and valves won't keep the intake manifold or throttle body gunk-free, so having one couldn't hurt.

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    Re: Tri-carb PCV valve

    Hi Drone Dog,

    Here is a writeup that presents what I had done to create a simple catch can (see shared link below). Although simplistic, it could be easily constructed and installed with the tube going to the air cleaner (in the picture) diverted to your copper manifold tube. Here is a picture of the mount used in my Healey (no modifications to anything).

    Ray(64BJ8P1)

    Figure 8.jpg

    https://drive.google.com/file/d/0Bx4...ew?usp=sharing

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    Re: Tri-carb PCV valve

    re: "i planned to start the engine with the oil cap loose just in case it has positive pressure. sound right or not?
    second, if i read all this correctly, at idle i should have very little if any vacuum at the oil filler cap.
    third, as i increase rpm, i should feel more vacuum at the oil filler cap."

    My BJ8 with PCV has noticeable vacuum at the oil filler port at idle. I believe the 'theory' with PCV is that the valve is mostly closed at idle, else it would be an intake leak and cause a rough idle. At or near WOT this 'intake leak' would be inconsequential so the valve opens up to pull more blowby out of the crankcase. Can't explain the vacuum at idle, unless the 'leak' from the PCV is larger than you'd figure. Note I installed the 'Nock kit,' which limits leakage at the dipstick port and filler cap.

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