cheap PVC valves?

What's wrong with cheap PCV valves? I remember reading here that they should not be used.

In theory if it fits tight and works at standard vacuum it should be fine. Healthy engines at idle all create 15-20 Hg of vacuum, at

2000 rpm 19-21 Hg of vacuum, and at full throttle near 0 vacuum. A healthy decelerating engine jumps to 21-27 Hg as the throttle is released. Or so it says in my vacuum guage instructions. The package of a cheap Canadian Tire valve says "The postive crankcase valve uses engine vacuum to pull harmfull vapours out of the crankcase and return them to the carburetor, where they are reburned in the cylinders". (That's harmful to the environment, not the engine, I assume.) Does a PCV value have to be more sensitive than the vacuum guage numbers suggest, and therefore specific to the make and model of vehicle?

Or is the objection that they do not last as long? The one I looked at today says it "meets or exceeds original equipment performance specifications". Those specs might not say anything about durability. The package says to replace the valve every year or 20k km, about 12k miles.

--

------------------------------------------------------------------------------ William R Watt National Capital FreeNet Ottawa's free community network homepage:

formatting link
warning: non-freenet email must have "notspam" in subject or its returned

Reply to
William R. Watt
Loading thread data ...

I have been using the CT PCV valves since the 70's and have never had a problem with them. I also highly doubt I have ever changed one within a year like the package says. I usually swap them when I swap plugs cap and rotor.

They 'are' vehicle specific though. They need to match the intake vent of the valve cover and manifold orifice for flow or you will get blow by appearing by not enough flow or have a lean idle condition from too much flow.

Some vehicles or engines like the carb Jeep engines are 'real' picky about having the right one in there.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's

"William R. Watt" wrote:

Reply to
Mike Romain

My original auto mechanics instructor agreed about "picky" and advised cleaning rather than replacing the PCV valve. This wasn't to save money. It was to insure the right part.

When I do any tune up work, I first remove the PCV and put >

Reply to
kgold

Interesting. I was told not to reuse the valve. I think it was because the spring might change over time. OTOH the manual says if you shake it and it rattles its okay. The old one feels sticky when I shake it. I don't know if that would be dirt or spring or both. I put it in a jar of solvent to see what happens.

--

------------------------------------------------------------------------------ William R Watt National Capital FreeNet Ottawa's free community network homepage:

formatting link
warning: non-freenet email must have "notspam" in subject or its returned

Reply to
William R. Watt

I have cleaned them before because the ball felt sticky and never had a problem, but given a choice and for the price I change them. Canadian Tire has always had the right match.

Oil blowing into the air filter is a sure sign the PCV system needs attention.

I buy a lot of old beasts and have bought more than one with a 'blown' engine, including my current Jeep CJ7 and all that was wrong was the PCV system. Charcoal canisters worn out can effectively shut down the PCV and cause a wicked imitation of a blown engine kicking out tons of blowby or just a plain gummed up PCV valve. So can a leaky or hardened grommet on the PCV.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's
Reply to
Mike Romain

PCV valves were originally introduced as an emission control device, prior to that raw crankase fumes were just dumped out to atmosphere via a road draft tube.

You must be very young and stoopid not to know this.

Reply to
Roger Blake

MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.