2.3 pcv

[YungICY]

I have an 85 2.3 that I rebuilt and converted to a Holley carb and among a bunch of the cork gaskets leaking I also have a vent tube coming off the oil fill cap that doesn’t have anywhere to route to do it just vents to atmosphere and adds to the leaking oil under the hood.

I have a pcv hose that comes from the lower part of the block, through a pcv valve and into the only vacuum port on my carb.

Can I plug the lower port coming out of block and just use the tube coming out of the oil cap? Any ill effects to doing this? Also would it be wise to run that routing with or without the pcv valve? It’s probably also relevant that I do have excessive blow by.

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[RonD]

The vent hose on the oil cap is there to SUCK IN fresh air, it would be routed to clean air side of air filter housing, so it sucks in filtered air, this is part of the Positive Crankcase Ventilation(PCV) system

PCV valve is used to pull blow-by out of the engine.
It uses a weighted valve to maintain consistent lower pressure in the crankcase using engine vacuum.
High vacuum(idle) pulls the weighted valve up which closes the valve a bit, lower vacuum(accelerating) lets the valve drop so opens the valve, pulling in more blow-by.

So PCV Valve must be clean and the correct one for the engine, it's vacuum source must be BELOW the throttle plate on carb engine, so either on the intake or the separator plate under carb.
Any ports above throttle plate are Ported Vacuums, and can not be used for PCV system

Blow-by vaporizes some of the oil on the cylinder walls as it pushes passed the rings, this is normal, cheaper oil causes more vapor, this is where all the oil vapor in an engine comes from.
Bearings and other engine lubrication never gets oil hot enough to vaporize.

Excessive blow-by, as rings wear out, will increase oil vapor, many add a Catch Can on the PCV hose to cool the oil vapor, condense it, so it doesn't end up coating the inside of the intake, then empty the catch can as needed.

If your Vent hose is not pulling in air then you may need a different PCV valve, one for a V6 or V8 engine, the excessive blow-by is too much for 4cyl PCV Valve.
Engine vacuum is the same on all gasoline engines, but PCV valves are different based on the blow-by created by the number of cylinders firing per RPM

Vent hose should have slight negative pressure, holds paper towel or Kleenex in place.
Dip stick tube as well, it should have slight negative pressure with engine running

 

[YungICY]

Ron are you adopting any adult children? You seem to be the guy that answers all of my specific/odd questions and you do it with the full explanation of things which I like.

I never knew valves were engine/ number of cylinders specific. I definitely have a positive pressure out of the cap vent tube. Looks like I’m gonna have to do some googling and find a valve that’ll fit my needs.

Thank you for your help once again. Have a merry Christmas and a happy anything else you may be celebrating.


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[RonD]

Thanks

Happy holidays to you and yours

 

[tomw]

Excessive blow-by will overpower the PCV valve, and feed the oil into the intake if it is bad enough. You might want to consider adding a catch can in line with the feed from the side of the block. It would have one tube from the vapor separator canister on the side of the block and another leading to the 'in' side of the PCV valve. Liquid oil droplets might fall to the bottom of the canister rather than blowing all over the engine and under hood area.
The tube from the oil fill cap should have at least a bug filter on it, but if the blow-by is really bad, maybe a catch can on it also. A plastic mayonnaise jar seems about the right size to catch oil for a while w/o need to empty every day...
You could throw a set of rings in for not a lot of money. Likely pay for itself in a few weeks if oil consumption is really bad, and you won't get pulled over for smoke nor dripping oil on the public highways. You'd need at least a head gasket, pan gasket, and likely cam cover gasket in addition to the rings. Clean up the valves a bit while apart, and it might run like new and have twice the horsepower and fuel mileage, and eleventy-seven times the distance between adding quarts/liters of oil.
tom

 

[Mark_88]

Oh, yeah...if i had all the money I wasted on blowing oil on the roads and in the faces of the people behind me I could rebuild two motors and buy some popcorn to watch someone install it for me...:0

 

[YungICY]

I had a filter on the cap vent but it ended up getting saturated in oil and causing oil to shoot out of a pin hole in the dipstick tube so that ended up coming off lol. The vent tube does have like some steel wool type material in the fat part of it so I figured that is sufficient enough for now especially since there is positive pressure in the motor.

A full rebuild is the eventual game plan. This is the first and only motor I’ve ever rebuilt so the oil leaks and blow by are almost the least of my worries on it. I’ve put almost 20k miles on it and it still runs like a raped ape. That being said though I need a smaller cam in it and most of the gaskets leak and ooze so when time and money permits, she’ll get a full rebuild that’ll take me half the time, cost half as much and be twice as more gooder lol as the first go around.

Amazingly I don’t lose much oil. Between gasket leaks and blow by I only lose about a quart every 1500 miles. But one look under the hood and it looks like the type that when you pull into the gas station you check the gas and fill the oil.


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[tomw]

I kind of missed where the PCV connects to the intake manifold, but will note that most carb mountings/adapters from FoMoCo had a port at the back to connect the PCV valve.
I doubt the connection to the carburetor is a good place, but could be wrong. Do you have a pic of where the PCV is connected?
If this thing runs ok, is it possible you have the wrong dipstick? I know my old truck, per the book, is supposed to take 6 quarts of oil when changing. When I put that amount in, it seems that the 1st quart will be gone within a few hundred miles, but after that it doesn't eat much at all, only nibbling around the edge of the plate, so to speak. So, I only put 5 quarts in when doing an oil change, and it is still happy. Might want to try running 1 quart low on the dipstick, still in the 'hash' marks, but not filled to the brim and see if the oil dispersal system still wants to work.
tom

 

[YungICY]

I kind of missed where the PCV connects to the intake manifold, but will note that most carb mountings/adapters from FoMoCo had a port at the back to connect the PCV valve.
I doubt the connection to the carburetor is a good place, but could be wrong. Do you have a pic of where the PCV is connected?
If this thing runs ok, is it possible you have the wrong dipstick? I know my old truck, per the book, is supposed to take 6 quarts of oil when changing. When I put that amount in, it seems that the 1st quart will be gone within a few hundred miles, but after that it doesn't eat much at all, only nibbling around the edge of the plate, so to speak. So, I only put 5 quarts in when doing an oil change, and it is still happy. Might want to try running 1 quart low on the dipstick, still in the 'hash' marks, but not filled to the brim and see if the oil dispersal system still wants to work.
tom

I have the pcv plugged into the full manifold vacuum source on the bottom plate of the carb.

My worst leak is coming from the cam shaft oil seal on the front of the head but the blow by is definitely contributing to the mess.

The biggest reason I have all of these leaks and blow by is because this is the first full motor I’ve rebuilt so I neglected to do some important steps when building it like, gapping the rings, making sure mating surfaces were clean for gaskets etc.

That’s why the eventual game plan is to just tear the motor down and do a full refresh on it. But for the time being, I’ll do what I can with the pcv to help cut down on oil loss and mess.


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[Mark_88]

Did you recently remove the cam shaft gear? If you did you might want to put a bit of thread sealer on the bolt before you install it because I had the same thing happen to my 2.3 when I replaced the head a few years ago. The oil was pouring down the front of the engine and I thought I blew the seal but it was just that the threads needed a bit of the sealer on them to stop the oil from coming out.

Only thing you need to watch there is some of them have an oil passage through them and if you block that off you could cause problems instead of fixing one...not sure where the oil goes to or if it is even a flow passage...but someone told me there was a flow passage and to make sure not to block it...which is easy enough if you are not careful with the thread sealer...too much is not good.

It could be the seal but something you can try before going that route...

 

[YungICY]

Did you recently remove the cam shaft gear? If you did you might want to put a bit of thread sealer on the bolt before you install it because I had the same thing happen to my 2.3 when I replaced the head a few years ago. The oil was pouring down the front of the engine and I thought I blew the seal but it was just that the threads needed a bit of the sealer on them to stop the oil from coming out.

Only thing you need to watch there is some of them have an oil passage through them and if you block that off you could cause problems instead of fixing one...not sure where the oil goes to or if it is even a flow passage...but someone told me there was a flow passage and to make sure not to block it...which is easy enough if you are not careful with the thread sealer...too much is not good.

It could be the seal but something you can try before going that route...

Thanks for the heads up Mark. I’ll have to get in there with a flashlight at take a close look.


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[Mark_88]

OK, to fix that it does require removing the timing belt and the cam gear but if it was missed on the reassembly then it is quite possible that is where your oil leak is coming from.

I also had a leak around the peg that the spring on the tension pulley pushes against. I left mine about a full turn out and there was oil coming from that area too. Just a minor thing but the peg hole is on an oil galley so there was a constant flow of oil around it and all that took was a wrench and a couple of turns in...check that too while in there...might be another source.

 

[YungICY]

I just took a closer look and the spray pattern makes it look like it is coming from the bolt. When you say thread sealer are you just referring to like loctite or like a plumbers paste or tape?

That’s good to know about the peg. I never would have guessed. Mine looks like it may be out a stitch so I’ll throw a wrench in there and see what happens.


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[Mark_88]

Just the plumbers thread sealer will work. I've used that on many bolts but you can also use things like locktite or similar products...I didn't like the idea of "locking" anything when I tore it apart so many times...but any sealant will work...the tape is easy to use and works great...plus my Dad taught me to use that so it was kind of what I learned...there are probably better things available these days...I've never bothered to research if I had something that worked.