[theYman]

Is it neccesary to change from a stock PCV when installing an agressive cam? How do you know what to change to? Is there a chart for given idle vacuum ratings? I would think a motor with 18 in. at idle would take a different one than one with 11in.
I was curious.
Trent

[chuckies76ta]

Trent: Your on the right track. As far as which one to use, I don't have any info for you. Maybe one of the more experienced folks will help out.

I did read about this a long time ago, that not all PVC valves are created equal..

Charles

[guccieng]

i've found that a gutted pcv works the best for me. it's alot more predictable and you can change the orifice if you get creative. i don't think the spring and 'rattling thing' need to be there. when there's vacuum, it draws air in. when there isn't, it vents out the blowby. we're not worried about emissions, are we? oh yeah, with a lopey cam that likes lots of fresh air at idle, it's a great alternative to drilling holes in your butterflies.

[b-man]

I have the stock PCV valve in my 8.6:1 '71 455 HO, H-O Racing HC-03 hydraulic cam with 244/252 @ .050,.550/.554 lift. Vacuum reading at idle is very low, usually under 8 inches.

Runs like a champ with one of Cliff's 800 Q-jets and a Rocky Rotella recurved points distributor (14 initial, 24 degrees mechanical, 16 degree vacuum can). Idles down nicely sitting in traffic, very predictable.

[Formulas]

That spring and rattle thing has a very distinct purpose..

The PCV valve connects the crankcase to the intake manifold from a location more-or-less opposite the breather connection. Typical locations include the opposite valve cover that the breather tube connects to on a V engine. A typical location is the valve cover(s), although some engines place the valve in locations far from the valve cover. The valve is simple, but actually performs a complicated control function. An internal restrictor (generally a cone or ball) is held in "normal" (engine off, zero vacuum) position with a light spring, exposing the full size of the PCV opening to the intake manifold. With the engine running, the tapered end of the cone is drawn towards the opening in the PCV valve, restricting the opening proportionate to the level of engine vacuum vs. spring tension. At idle, the intake manifold vacuum is near maximum. It is at this time the least amount of blow by is actually occurring, so the PCV valve provides the largest amount of (but not complete) restriction. As engine load increases, vacuum on the valve decreases proportionally and blow by increases proportionally. Sensing a lower level of vacuum, the spring returns the cone to the "open" position to allow more air flow. At full throttle, there is nearly zero vacuum. At this point the PCV valve is nearly useless, and most combustion gases escape via the "breather tube" where they are then drawn in to the engine's intake manifold anyway.

[theYman]

Aother posting made me wonder and I was curious. I noticed with my car idling I can grab the PVC hose and feel it "clicking" almost a vibrating feeling. I was thinking the spring in my valve might be too strong and the valve was open and closing rapidly and maybe affecting idle.
Trent

[Tom Vaught]

Get a PCV valve for a 425 HP corvette or a 1970 W-30 Oldsmobile w 455 engine and you will be just fine.

Tom Vaught

[theYman]

Originally Posted by Tom Vaught

Get a PCV valve for a 425 HP corvette or a 1970 W-30 Oldsmobile w 455 engine and you will be just fine.

Tom Vaught

That's EXACTLY the PVC I was going to purchase and test. 69 corvette 427 tripower. Thanks.

[David Jones]

http://forums.maxperformanceinc.com/...&highlight=pcv

Read this thread. You'll find no numbers. You'll find no specifications. You'll find no cross references, because there is no info to cross reference. Best thing you can do is as others have suggested. Select a valve designed to work on a vehicle with a "big" factory cam. Then inspect the markings on it compared to others the parts store has in stock. Who's to say they aren't all the same these days?

[theYman]

If I dont find a difference in them,I might take one apart and cut the spring.

[Tom Vaught]

Quote:

"That's EXACTLY the PVC I was going to purchase and test. 69 corvette 427 tripower. Thanks."

Make sure you get the one for the Rectangular Port heads (435 HP)
vs the 390 HP Oval Port head as the camshaft is smaller in the 390 HP version. The Olds W-30 had a big camshaft (328 advertised duration) in the 455 engine. Lots of thump.

Tom Vaught

ps All of the old HO Racing Distributor Vacuum Cans were based off the Corvette large camshaft Distributor Vacuum Diaphragm Cans.

Tom Vaught

[Region Warrior]

THANKS for the reminder.
I was gon'a order a couple a few months ago, but they come per 10 from GM.
My cost would be $60.11 plus tax.
One of our AC-Delco suppliers was check'n around to see if any other store got stuck with some.
Have to ring thier bell.

[66GTO Jim]

Originally Posted by David Jones

http://forums.maxperformanceinc.com/...&highlight=pcv

Read this thread. You'll find no numbers. You'll find no specifications. You'll find no cross references, because there is no info to cross reference. Best thing you can do is as others have suggested. Select a valve designed to work on a vehicle with a "big" factory cam. Then inspect the markings on it compared to others the parts store has in stock. Who's to say they aren't all the same these days?

I found cross reference info on the Purolator and FRAM websites:

http://www.purolatorautofilters.net/...tionGuide.aspx

http://www.power-21.com/FramPower21i/

The basic Pontiac "through the valley pan" PCV is AC/Delco CV679C which is also Purolator PV679 or FRAM FV112.

The Chevy 427 3x2 "valve cover mounted" PCV that has been recommended in posts here shows as Purolator PV736 and Fram FV181. These cross reference on these sites to the AC/Delco CV736C, CV773C and CV876C. Interesting that the AC/Delco site shows the 427 4bbl as CV736C and CV773C, but there is no listing under the 427 3x2 although there are air filters etc for this engine. Searching the AC/Delco site I get hits on CV736C and CV773C but not on CV876C. I suspect AC/DELCO CV876C is for the 427 3x2 and is no longer available. Purolator PV736 and FRAM 181 are really replacements for the 427 4BBL although they cross reference to the 427 3x2.

Also, checking my parts stock, I had a Purolator PV679 (stock Pontiac) and also a FRAM FV182. The FRAM 182 has a larger bore than the PV679, so I decided to see what it cross referenced to. Not one of the sites listed or cross referenced a FRAM FV182, including the FRAM site! I have FV182 filter and the original FRAM package marked FV182 in my hand. Weird huh? Anyone have any old listing for a FRAM182 PCV valve and what engine/vehicle it was designed for? Any info appreciated.

Jim

[Region Warrior]

None of those are the correct ones.
Hmmm...anyone want to buy some?
I can still get'm from GM.
Just checked, thier only stocked at on location, and doesnt look like they'l be available much longer.

[chuckies76ta]

Originally Posted by Region Warrior

None of those are the correct ones.
Hmmm...anyone want to buy some?
I can still get'm from GM.
Just checked, thier only stocked at on location, and doesnt look like they'l be available much longer.

So, What's the part number...??

Thanks
Charles

[66GTO Jim]

Originally Posted by 66GTO Jim

Anyone have any old listing for a FRAM182 PCV valve and what engine/vehicle it was designed for? Any info appreciated.

Jim

Answered my own question. FRAM FV182 is for mid-eighties GM V6 engines. Probably left over from one of my buddies Grand Nationals. Jim

[PITTSBURGH 64]

NAPA # 29506 Heavy Duty- 1968 427
I don't know if it's the valve cover pvc or not...

BTW) I know a few guys here that don't run a PVC valve at all. They've been doing this for years..

I removed mine and plugged the intake port today just to see what would happen, my 60919 cammed 462 seemed to run with less off idle snap then usual. I guess would need to tune it in this state. I did notice a 1/2" of vacuum gain. I was getting about 11" in drive.

I have a bung soldered into the high vacuum side my air cleaner with the two valve cover breathers teed into it..

[David Jones]

Part numbers can be cross referenced any number of ways. That's not the problem.

A guys got a 472 with a big cam and an auto trans. 10.5" vacuum. Not much about the engine that GM would recognize.

What PCV valve does he need?

Another guy has a 406 that'll pull 6400 rpm. Solid cam. Aluminum heads. Nasty lope.

What PCV valve does he need?

We've got this great list of PCV valves available but ABSOLUTELY no information on their operating parameters. Choosing your PCV valve based on the fact that some older car with a big factory cam used it ain't exactly the perfect method.

There are no specifications posted about PCV valves anywhere.

[guccieng]

that was my whole point about running a gutted one. no need to get part numbers on a part that won't be right in the first place. i use a billet specialties pcv and removed and discarded the internal valve. i can put restrictions inside the two-piece pcv if i want to change the flow of air. it acts as a wonderful vent that lets cooler air into the crankcase and removes corrosive and possibly flammable vapors under any vacuum condition (more vacuum, more flow of course). another good side affect is that it will lean you out for cruising because the front vac port of your carbs baseplate will be letting air in the primaries and allow you to run with less throttle and give you some better gas mileage (i still had to jet down my primaries, so it's not that much leaner. this is with wideband tuning). without vacuum, the blowby is allowed to escape though a breather or into the carb to be burned. it's simple, doesn't get clogged, and will never need replacement. finding a pcv for a modded engine is futile. i'm just trying to help here.

[Tom Vaught]

Originally Posted by PITTSBURGH 64

NAPA # 29506 Heavy Duty- 1968 427
I don't know if it's the valve cover pvc or not...

BTW) I know a few guys here that don't run a PVC valve at all. They've been doing this for years..

I removed mine and plugged the intake port today just to see what would happen, my 60919 cammed 462 seemed to run with less off idle snap then usual. I guess would need to tune it in this state. I did notice a 1/2" of vacuum gain. I was getting about 11" in drive.

I have a bung soldered into the high vacuum side my air cleaner with the two valve cover breathers teed into it..

The one thing that a crankcase ventilation system does for you is remove a great portion of the corrosive gases from the crankcase.

If you drive your car very little and change the oil on a regular basis
(say every 1000 miles), then it probably will not make a difference. The whole idea behind the crankcase ventilation system had little to do with emissions vs it worked so much better than the road draft crankcase ventilation systems.

Tom Vaught