Thread: Pvc

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PVC valve, I thought I`d touch bases with you guys on this, never installed one on my 406, but rethinking this, with the holley 670 PVC port plugged will make it idle on the rich side...? Am I thinking in the right direction here, and if I install one, it should lean out my idle....... what size would I need, can I test the vaccum at the dipstick tube to see if I`m getting say at least 3lbs with a vaccum tester then I should be good with what ever size I buy, but may try to size out the oriface with an adjustable small gate valve for testing purposes to determine the minimum size. Whats your thoughts...?

Originally Posted by 406Rich

PVC valve, I thought I`d touch bases with you guys on this, never installed one on my 406, but rethinking this, with the holley 670 PVC port plugged will make it idle on the rich side...? Am I thinking in the right direction here, and if I install one, it should lean out my idle....... what size would I need, can I test the vaccum at the dipstick tube to see if I`m getting say at least 3lbs with a vaccum tester then I should be good with what ever size I buy, but may try to size out the oriface with an adjustable small gate valve for testing purposes to determine the minimum size. Whats your thoughts...?

I'm thinking that you're carbs tune or "adjustability" will probably change but I don't think you should be planning for it.. If you're carb jetting is rich and then you add more air, you're engine rpm will rise and hopefully you can turn the idle screw down to lower the rpm..

To work properly, the valve cover opposite the pcv valve will need an air inlet breather, so no, you shouldn't be able to pull a measureable vacuum.

Lastly, whatever base engine you started with is what I'd purchase for a new pcv valve, for instance my 347 uses a valve from a 302.

I had a link that gave a real good explanation of the pcv operation and will explain it better than I ever could, I'll see if I can find it and share it here for you..

I was unable to find the address for the site I was thinking of. It had been the best write-up regarding PCV Valves and crankcase ventilation in general. It had been done at a Toyota factory site but it's no longer available.

But sites like ehow.com or ask.com, google all have a wealth of info to share..

pcv valve in one valve cover and you need a breather on the other valve cover and I would bet a pcv for a 1970 396 chevelle would put ya just about right. But I'm thinking if your rich it's probably not gonna lean it enough. To check pcv function, pull the breather and check for suction there.

When set this up I`m going to run it thru a fuel filter down low just to minimize the amount of oil into carb, but still might put a vaccum gauge on the dipstick tube, with the breather on the left and pvc on the right to see what vaccum it does pull, might try to minimze the orifice size on the pvc, but will start with a big block as said by Hworrell...

Originally Posted by 406Rich

When set this up I`m going to run it thru a fuel filter down low just to minimize the amount of oil into carb, but still might put a vaccum gauge on the dipstick tube, with the breather on the left and pvc on the right to see what vaccum it does pull, might try to minimze the orifice size on the pvc, but will start with a big block as said by Hworrell...

Fuel filter is not needed valve cover needs a baffle (should already have provisions unless its a really old style valve cover) and you'll never read any vacuum @ the dipstick unless you plug the breather.

Old school valve covers with roller rockers, no baffle in place, no room for one, at least not on the top unless I can get creative.

I've used some of these before with great results..

Valve+Cover+Baffle - JEGS High Performance

or,
http://www.summitracing.com/search/p...cover%20baffle

Those aren't that old school ! Your breather is already in place, and I would bet there is a oil baffle under it. I won't swear to it but I would bet there is a knockout plug on the other valve cover with a oil baffle already under it. If that's the case ( and I bet it is) all you need is an pcv grommet and the pcv valve and of course your vacuum plumbing.

Holley Performance Products SB Chevy M/T Valve Covers - Polished*241-82

No, no baffle, I spent many hours cleaning ( the orange Paint ) and polishing them, 10 dollar swap meet special, I can make a baffle if needed, I`ll have to measure the amount of room I have, I know its not much though. Same breathers on both sides.