Question to any corvette enthusiasts.

bought valve covers online and went to install them. Any ideas what I need to do with the pcv hose going to my old valve cover. New valve cover doesn’t have. I put a bolt and clamp in it to plug.

 

Buy the right valve covers with PCV provision, or drill the new covers to install a grommet and the valve (along with internal baffle system). Capping it off is a really bad idea. Better idea is to ditch the cheap, incorrect, Chinese covers you bought and buy the right parts.

 

Thank you , the hose to the air cleaner can I remove that and run the pcv valve into that

 

You have to have both: The PCV pulls crankcase air out of the driver's side valve cover, and the passenger side valve cover must have an air inlet to provide the fresh air inlet. It's a complete system - you can't run it with 1/2 the parts.

 

Thank you, a lot of help. Also I’ve been researching. The oil cap has a breather on it. So I was thinking re routing the pcv valve to the opposite side of oil cap . Also eliminating the hose to the air cleaner. Any thoughts?

 

You still need a hole in each VC. A vent in one to draw fresh air in, and a PCV valve in the other to draw oil mist and crankcase vapors out.

Use the right VCs. Or LT-1 style originals or repros. I tossed all the Edelbrock garbage a PO had put in my 79 and reverted back to GM blue steel VCs. All chrome does, other than leak, is point out how dirty the rest of your engine compartment is.

 

Thanks bikespace, so should I just re route the pcv valve to the opposite side? Since the oil cap has a breather. And eliminate the tube to the air cleaner in picture I posted. Thanks for all the advice

 

You need the breather and the PCV valve on different heads. There are diagrams floating around, including on this Forum, that imply that the way GM designed it (breather on starboard head, PCV on port) is preferred due to the crank rotation direction. I'd keep it that way if it's easy (the oil fill side doesn't matter). Otherwise, as long as they are on different heads.

 

Looking from the front of the car.


The baffle prevents oil from being drawn up but lets the air out.

 

Buy the correct valve covers that have the provision for a PCV in the driver's side and the inlet vent in the passenger side and quit trying to Bubba your setup to accommodate the wrong valve covers.

 

holy **** the people on C3 section are smarter than the C4-C8 section and all the turbo & import forums put together

good F@#(*@# job guys

 

If you have a basic understanding of how a positive crankcase ventilation system is supposed to work this is truly just childs play.
no you should not have a vented oil fill cap. That was used before PCV. Aftermarket covers can work fine. But the correct ones.

 

Changed the configuration early this morning. Next changing the master cylinder. Any advice.
Hey guys these pics look better ?

 

Question , I originally knocked out hole for base of air filter tray. I removed gromit and put it back . Under the air filter the base has hole. Is that ok? This is the base. So it sits like this but open hole in side

 

so you have an open hole to pull air in bypassing the air filter? if so no, you'll want to block that off with something, anything..

 

Just JB Weld a quarter to the UNDERSIDE of your air cleaner to cover that hole. Cost .25.

 

Might help if you understood PCV valves, operation, theory a little bit more.

>Here's what I've read and learned about PCV valves over the years:

A PCV valve provides a controlled / calibrated air leak at certain engine regimes, mostly mid-throttle (cruise) in order to continually recycle/combust the "air" in the crankcase, avoid the buildup of moisture, etc.

It replaces the older style breather hose /filter assembly which merely dumped that stale "air" overboard, including any oil mist it contained. Blowby, etc. was a significant source of air pollution back in the day hence the addition of PCV valves sometime in the mid '60s. EPA?

A PCV valve is vacuum operated. It opens at PARTIAL vacuum levels. Not high vacuum levels like at idle, nor at zero vacuum level like at full throttle.
An internal spring determines the vacuum level at which it opens.

Opening at idle would have major impact on the idle speed, mixture, etc. You might even get a feedback loop, surging idle. I disagree with those who claim it should
"remain a little open at idle"

Mfr's spec'd a certain PCV valve, opening at a certain vacuum level, to go with certain carburetors, compression ratios, setups, etc. It had to be calibrated to prevent an over-lean
condition when it did open.

Many newer models are adding an oil catch-can to the PCV system, in order to trap & condense oil fumes, and drain them back into the crankcase. This is especially
true of super/turbocharged models which will otherwise tend to "suck" in a lot of oil fumes at high level of boost, LOWERING the effective octane level of the fuel, and
reducing power, supposedly. It will also reduce oil consumption.

When you've got an engine with who knows what mods, non-original carburetor, etc. you're shooting in the dark on PCV valve selection. If you feel it's opening excessively
you could put a restrictor in/on one of the hoses. If it's not opening as much, as in OP's case.... try some other ones?

There is a vintage PCV valve tester I see on Ebay now and then that SHOWS the pressure at which it opens. You could do similarly with a vaccum pump, gauge, etc. till
you find the one with the opening pressure you want.

In general you want the PCV system to maintain a SLIGHT vacuum in the crankcase. Suck out more "air" than is blowing past the rings. Why? Because if you allow the crankcase to pressurize, even slightly, you will get oil leaks around and past every seal, every possible place.

 

Thank you for your helpful post. It is good to see people learning and re-teaching, this is good use of forum time spent.

I would like to teach you some additional things, so you can help even more with advanced knowledge. I teach engineering fundamentals at university, my background MS bioengineering PhD mechanical engineering, 20 years building and tuning forced induction vehicles with all types of engines, 1.8L 2L 2.4 2.5 2.6 3.0 etc... My first twin turbo V8 was in 2001, I wrote software to auto-tune the engine back before widebands were available affordably at hobby level. I've since tuned every kind of stand alone and every possible setup and got to the point where it all runs together. I hope you will realize some new thoughts here in this discussion.



Here is diagram from publish paper on general pcv valve operation





The PCV absolutely must be open at idle. Otherwise, blow-by gas will contaminate engine oil. The purpose of PCV in performance setups is to maintain cleanliness, prevent deposits, prevent excessive wear and eventual failure. The more suction we can apply to the crankcase to maintain some vacuum at all times, not just idle but always, the cleaner the crankcase will remain, the more quality oil will maintain, the longer the engine will last. Higher mileage. The PCV valve contains a nozzle which prevents high vacuum from causing excessive mass flow rate to the engine; thus it cannot significantly adjust engine idle during operation. That is, there is some influence, but the influence is static and built into the engine idle condition, it will not cause idle to wander because max mass flow rate is somewhat constant.

To bring this one step up, in performance apps with V8 engines using low silicone alloy forged pistons, large piston to wall clearances, have high leakdown rates while cold and warming up, I will use 2x PCV valves, a twin setup. Double the flow at idle to the intake manifold to achieve a satisfactory clearance of blow-by gas from the crankcase is ideal. The goal behind PCV is to maintain a vacuum at all times in the crankcase. A slight vacuum from 1.5" Hg to 3.0" Hg is fine, approx 1 to 2psi of vacuum is great for wet sump operation. Part of setting up a tuning a high performance engine that does not use a vacuum pump (belt driven) is to measure the crankcase pressure for idle/cruise/WOT and Manually SET the crankcase pressure using these techniques, 1. Add PCV valves or adjust PCV orifice as needed 2. Adjust throttle valve pressure drop or compressor inlet pressure drop as needed to maintain crankcase vacuum (PCV).



Many OLD models include this type of external oil air separator. For example 1992 sr20det 2.0L Turbo OEM has this external 'can'. I show picture



The purpose of these external separators is to make up for insufficient separation inside the valve cover (or valley cover for a V8). In other words, these engines all have INTERNAL air/oil separators, but during testing the manufacturer found the internal design was insufficient and either did not want to re-design (or could not make it better) so they attached an external separator which does the same thing, routes oil back to the pan somehow.
The point here is,
1. These are not catch cans because they do not catch anything. Calling them a 'catch' is a misnomer. It is an air/oil separator, identical to what is inside the valve cover, just outside the engine.
2. In many cases the newer models delete these external separators as technology improves, for example 95-02 sr20det does not have any external separator, the internal baffle system improved in those models and the engine output increase by 50hp using a larger turbocharger from the factory. So this isn't really a 'new' thing, it is only needed wherever deemed necessary such as very low to the ground dry sump systems installed to vehicles which expect to see high G-force cornering or other oil-sloshing influence where an external separator would guarantee the mostly complete separation of oil from air, but not CATCH it, merely return the oil to the pan. The design itself is over 20 years old, Nissan and Subaru used it, among others.

The correct way to avoid 'guessing' is to measure the crankcase pressure. This is the most overlooked and under appreciated pressure on the vehicle in todays performance community. Crankcase pressure is just like tire pressure, fuel pressure, coolant pressure, oil pressure, boost pressure, etc... It must be SET SPECIFICALLY to fall within some range. You must connect a gauge or map sensor to the crankcase and measure it, then adjust as needed. This is what I Want to show you.
Here is a video from my latest project, a free junkyard 200k miles motor 600rwhp turbo, I Put 50,000 miles on it already so 250k miles total. The engine can stay clean and oil leak free because I MEASURED the crankcase pressure and ensured it will reach some target specific for my application (street strip)

This is absolutely true. The pressure of crankcase must remain BELOW atmospheric at all times while engine is running. There are many consequences.
1. As you say, it will leak engine oil from every possible place. This is obvious to us. But what else is there?
2. Piston ring tension forces and ring switching (advanced topic) are dependent on crankcase pressure.
High crankcase pressure causes early ring switching and reduced ring tension, which allows oil to invade ring pack, increased oil consumption, increased blow-by, increased deposits forming around the rings and especially the back of the ring where gas vector component forces are supposed to apply evenly for tension to cylinder wall.

3. Blow-by gas partial pressure component of dissolved gasses in engine oil (gen chemistry) increases with pressure as with all gas. In other words, the higher the pressure, the more dissolved gas can be maintained in the engine oil. Just like the CO2 in a coke bottle, at high pressure it will remain dissolved. But when the cap is removed, the gas can escape thanks to low pressure above the liquid. And so it is with engine oil and blow-by gas, by keeping low pressure in crankcase, the gas can more easily avoid and escape the liquid engine oil phase, and stay out of the oil circulation where the partially combusted hydrocarbon products of combustion form deposits leading to excessive wear and eventual failure.
Here is gen chem book showing this topic




4. Similar to #3, blow-by gas has a scalar and vector relationship with respect to pressure and kinetic energy velocity component (sorry its a little fluid mechanics). The pressure component is a scalar, meaning it has no direction. Like inside a tire, the gas molecules bounce all directions at once, they collide together and collide with the container in elastic collision. When blow-by gas is ejected from the ring/piston, the pressure is a scalar with no direction, meaning it can pressurize the entire crankcase the same way it could pressurize a tire. The goal of PCV is to provide kinetic energy (velocity component vector) to blow-by gas molecules which force them to organize, and form a moving column of air, exactly as pictured above in the OEM diagram, which forces air to move in an organized fashion from one side of the crankcase to the other (By peterbuilt: "does this help?"). It is no accident or coincidence that the engineers maintain a steady moving organized flow of air from the air filter through the crankcase to the intake manifold suction during idle and cruise operation. This moving column of air contains kinetic energy which 'collects' blow-by gas as it is ejected from the rings and moves those gas molecules back into the intake system where it can go right back where it came from: the cylinder. And quickly, high velocity, hot gas, rapidly moved back to the cylinder, before it can interact with engine oil. In this way it is similar to #3: It is an engineer'd part of the PCV operation which all engines and tuning efforts are determined to realize the energetics of collecting blow-by gas quickly and dealing with it before it can reduce oil quality and form deposits and so forth.

So this is it then. PCV doesn't just prevent oil leaks. It assists the piston ring function, helps to seal the cylinder, helps reduce blow-by. It keeps the ring pack clear from oil and prevents ring flutter. It keeps oil clean and helps to remove blow-by gas from engine oil. It prevents deposits which lead to excessive wear and eventual failure. PCV enables high mileage. The air filter is just as important but that is a new section of discussion. Between air filtration and PCV an engine can reach a million miles.
PCV is the most important system on an engine in my opinion.