Plastic PCV valve vs Metal PCV valve?

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Lord Sparky

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My plastic PCV valve is working fine but I thought I’d buy an original NOS in-bag L351 metal PCV valve for authenticity. The wider plastic PCV valve appears to work better than the metal one, much more air flow and a much better seal when you blow into the carb side end. The plastic PCV valve also makes more noise when you shake it.

What are your thoughts?

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The metal one should make noise when you shake it, you might need to tap it a few times or clean it.
I like originality.

Alan
 
Either will work, I run the larger type. I believe the small one bolts into a housing and is installed in the valve cover stovepipe. 65'
 
I believe each one has a different grommit. The metal is early, up to 70? Not sure when the switch was. Metal is more durable, of course. If the rings and valves are in good shape, the less PVC flow you need.
 
The actual valve itself is metal in both cases. The 'plastic' is just a 90* elbow that has been added for hose routing.
 
The actual valve itself is metal in both cases. The 'plastic' is just a 90* elbow that has been added for hose routing.
I am sticking with the plastic PCV valve for now as it provides more forward air flow and the check valve to stop back flow has a better seal. It is interesting that the hose from the air cleaner to the oil cap is larger than the hose from PCV valve to carb with the PCV valve reducing flow further.
 
Glad you have one and "Very Smart"!

I have found, Based on cam, carburation and many more situations, you may need to experiment to find the correct balance required!

PCV's are fairly cheap and finding the correct balance is not that difficult or expensive! Authenticity is nice when it works!
 
Those two PCV valves (in the picture) use different grommets, right? Is your problem that the smaller valve nipple is leaking and the plastic one isn't? Both grommets widely available.
 
The hose to the A/C needs to be larger because it is operating under atmospheric pressure, whereas the PCV hose has engine vacuum [ suction ] applied to it.
 
I am sticking with the plastic PCV valve for now as it provides more forward air flow and the check valve to stop back flow has a better seal. It is interesting that the hose from the air cleaner to the oil cap is larger than the hose from PCV valve to carb with the PCV valve reducing flow further.
Not really on the hose sizes, The factory setup was as such. Positive flow and evacuation of the crankcase is all that matters! Cam lift and more can effect this much, and sometimes a Vacuum pump is required.

Most do not and finding a good balance that gives a smooth idle is the ticket! JMO!
 
Not really on the hose sizes, The factory setup was as such. Positive flow and evacuation of the crankcase is all that matters! Cam lift and more can effect this much, and sometimes a Vacuum pump is required.

Most do not and finding a good balance that gives a smooth idle is the ticket! JMO!
Yes, I read that idle can be quite effected by clogged hoses or stuck PCV valve. Interesting design!
 
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