What happens if you install the wrong PVC valve?

[brumbach]

My 65 vette has a 1968 327 block with 66 heads and manifold. According to the previous owner, he built the engine to the 66 327/350 hp specs. Because it's a 68 block, the crankcase is vented at the valve covers. I recently replaced the pvc valve. When I went to the local autozone to purchase the replacement, the salesman had one for a 66 and another for 67. I chose 67 since the 66 vette is not vented via the valve covers. Could my selection of the wrong pvc valve cause problems or damages with the engine? Finally, how can I be sure of the correct pvc valve if correct selection is critical to the welfare of the engine? It's too bad the engine is not correct for the year but someday it will be! Sure will be a lot easier in purchasing the correct part.

 

[studiog]

I'm not an expert on PCV valves but I don't think it is too critical but could have a minor effect on carb and vacuum related systems. Maybe John Z will come to the rescue soon.

 

[Firemist1]

The 66 & 67 PCV valves screwed into the filler neck and flowed backward from all other small block applications that followed after those years. If you put the wrong one in, the crankcase will build up pressure and your fuel mixture may be affected. If you are going to vent from the valve cover, just get a 68 or later PCV valve for a small block that fits the grommet well and you should be OK. I think they all flow about the same amount of air.

 

[JohnZ]

'66 & '67 PCV screw-in valves flowed in the same direction (from the crankcase via the oil fill tube, through the valve and hose, to the carb base inlet) as the '68 and later cars did (from the crankcase via the driver's side valve cover, through the push-in grommeted valve and hose, to the carb base inlet). Just get the PCV valve that's designed for the '68 valve cover application - there's not a lot of difference in the orifice size and check valve spring tension between any of them. In any event, engine damage isn't an issue as long as you can shake the valve and it rattles.

 

[brumbach]

Thanks you all a bunch. Bill

'66 & '67 PCV screw-in valves flowed in the same direction (from the crankcase via the oil fill tube, through the valve and hose, to the carb base inlet) as the '68 and later cars did (from the crankcase via the driver's side valve cover, through the push-in grommeted valve and hose, to the carb base inlet). Just get the PCV valve that's designed for the '68 valve cover application - there's not a lot of difference in the orifice size and check valve spring tension between any of them. In any event, engine damage isn't an issue as long as you can shake the valve and it rattles.

 

[skids]

Hey JohnZ, does it matter if pcv valve is on right side. I also have a 68 block in my 64, and have valve on right side. I don,t think it would matter. Thanks.

 

[JohnZ]

I don't think it really makes a lot of difference on a normal street engine, but the system was designed to put the PCV valve on the left (driver's) side originally; the oil throw from the crank and rods is UP towards the bottom of the oil drainback passages on the right side, and DOWN on the left side, so the valve was placed on the left side to reduce the possibility of oil pickup at high rpm.

 

[brumbach]

In my case, it's much easier to have the pcv valve on the passenger side cover because the connection to the carb (holley 4160) is on that side too. To install on the driver's side would mean running the connecting hose completely around the carb.

 

[JohnZ]

In my case, it's much easier to have the pcv valve on the passenger side cover because the connection to the carb (holley 4160) is on that side too. To install on the driver's side would mean running the connecting hose completely around the carb.

Which is exactly how the production PCV systems were done - the hose came from the front of the driver's side valve cover, around the front of the carb, to the PCV hose nipple on the passenger side of the carb.

 

[brumbach]

Do you recommend I configure this way?

Which is exactly how the production PCV systems were done - the hose came from the front of the driver's side valve cover, around the front of the carb, to the PCV hose nipple on the passenger side of the carb.

 

[JohnZ]

I would, only because millions of them were designed and built that way, and worked just fine; I only re-engineer things when it's necessary for other reasons.

 

[brumbach]

I would, only because millions of them were designed and built that way, and worked just fine; I only re-engineer things when it's necessary for other reasons.

Well it's been done but now I've got another question. Although I've got the correct breather for the car (1965), instead of connecting the passenger valve side to it, I've got a breather installed directly in the valve cover. The car came set up that why but the reverse, i.e., breather on the driver side valve cover and the pvc valve on the passenger side. Smoke is now coming from valve cover breather whereas it did not when located on the driver side. What's going on? Have I uncovered a problem by correcting the configuration. I haven't driven the car since moving the pcv to the correct side other than starting it and allowing it to idle. Should this clear up after I've driven the car at higher rpms?

 

[brumbach]

Might've spoke too soon. Couldn't resist and took her out for a spin. Ain't smokin anymore. Maybe it had been run so long with the pcv valve on the opposite side that she had to just get used to the change. Feels good and running just fine. Bill

 

[brumbach]

Since I've changed things about, I've been observing engine gaskets for possible oil leaks. Sure enough, oil is beginning to leak from around the rear and front of my intake manifold. There were no leaks before I switched the pcv valve to the drivers side. Could the relocation of the valve result in a build up of crankcase pressure thus causing the gasket to leak? A simple fix would be to return the pvc valve to the passenger side but I'd rather leave it as is and install a new gasket if an increase of pressure is expected (as long as it doesn't exceed the holding power of a new gasket) What do you think?

I would, only because millions of them were designed and built that way, and worked just fine; I only re-engineer things when it's necessary for other reasons.

 

[JohnZ]

If there are no restrictions in the big intake hose from the air cleaner (or a valve cover breather, if that's what you're using) and none in the PCV hose from the oil fill tube (or the other valve cover) to the carb and the PCV valve is working, you won't have any crankcase pressure unless the rings are really bad and you have more blow-by than the system can handle. Can you post a photo (without the air cleaner) of how your system is configured?

 

[brumbach]

If the rings were bad, wouldn't the problem be evident regardless of the location of the pcv valve, i.e., passenger or driver side valve cover? I'll try and get pics out tomorrow, my digital camera is at the office. I'm wondering if the pcv valve might be causing the issue. It's new (which started the whole dialog). I might put the old valve back in and see if the leak continues.

If there are no restrictions in the big intake hose from the air cleaner (or a valve cover breather, if that's what you're using) and none in the PCV hose from the oil fill tube (or the other valve cover) to the carb and the PCV valve is working, you won't have any crankcase pressure unless the rings are really bad and you have more blow-by than the system can handle. Can you post a photo (without the air cleaner) of how your system is configured?