Doug Brandon

May be a dumb question, but what would the car run like with one that is not working (street driven Vette). Thanks.

theandies

Normally if your PCV system is not working you will start to develop oil leaks because the block will become pressurized and force the oil past seals and gaskets. Take the PVC valve off and shake it, if it rattles then the valve is working correctly. PVC stands for Positive Crankcase Ventilation. If you want to troubleshoot it and have the PVC valve pressed into a rubber grommet on one of your valve covers, then you can just temporally remove the valve and let the engine vent into the engine compartment (but if your valve covers don’t have baffles then it may spray oil all over the place and you can get dirt in the engine this way, or you can go but a engine breather cap for your oil filler hole and take your oil filler cap out an place the breather cap in its place.
John

Doug Brandon

Thanks, I think I made the mistake of using a PVC valve one side and a breather on the other. I think my manifold vacuum is just pulling in air from the vented cap and not really relieving pressure from the crankcase like it is supposed to. I have not driven the car recently, but will replace the breather this weekend and give it a go.

71vettman

Using a pcv valve on one side and a breather on the other shouldnt cause you any problems if both are working properly.

bigvette1

Let me piggy back on this topic. Is it possible that if an engine was designed for a rubber plug (73 w/emissions) on one valve cover and the PCV on the other, that using a breather will cause oil in the intake? Or if the PCV were the wrong one? I know this is wierd but 3 sets of gaskets and two different manifolds and the same symptom of oil in the intake being burned makes me think something else is going on. Ideas?

7Bob3

The PCV valve is a controlled vacuum leak that you tune around when the valve is funtioning properly. If it is plugged the car will probably not idle or be very low and rough without adjustment. Rich. If some how the restriction was completly removed the idle would raise and the motor would pop and spit under load. Lean.

To the piggy back question. on a street car we are not trying to draw a vacuum on the crankcase with motor vacuum. If we did we would have oil in the intake. To work, assuming cylinder walls, valves and valve guides are in good shape, there needs to be a fresh air source opposite the PCV valve. On the stock setup this was accomplished with a hose and fitting from one of the valve covers to the air filter. If this is missing you can run a fancy breather in it's place, but you can't close the system to the PCV valve.

john's '81 mouse

you can check pvc valve for proper function simply by removal while engine is idling, and then placing your thumb / finger over the pvc valve inlet, it should suck your thumb finger tight against the valve and engine speed should change / decrease once you plug the valve.

adamdinat

the PCV valve on my car was kinked to clear another vacuum port. I smelled oil in the garrage after a drive. I unkinked the hose and the smell is gone. I assume a failing PCV may have the same symptom

bigvette1

Thaks Bob for the update. My PCV works fine with the finger test. I have the breather line from the air cleaner to the valve cover + a filtered breather car. Probably not needed by looks good.

So...... I either still have an intake leak sucking oil or the engine is getting tired most likely with guides as the compression is pretty good. Oh well, I was planning a major freshen up this winter.

john's '81 mouse

Quote: "So...... I either still have an intake leak sucking oil or the engine is getting tired most likely with guides as the compression is pretty good. Oh well, I was planning a major freshen up this winter. "

If sucking oil past valve guides, you could stop most if not all oil consumption by simply installation of new positive valve guide seals, sold by crane, felpro, and others. Not a difficult job, and can be done with heads still on engine.

Woodstoc

I just did this project, used an air compressor with a fitting for the spark plug hole, overhead valve spring compressor ($26.00 at Autozone) and a seal kit from Comp Cams. Took about 2 hours to do, not hard. Just remove plug, install fitting, pump up to about 90 psi, use spring compressor after rocker removal, pry off old seal, seat new seal, reverse assmb.

Solved the smoke problem. :iagree: