LIQUIDZ28

So my buddy here at work has a 93 T/A with an LT1. Had some broken exhaust mani bolts that needed to be tapped out and he felt he would leave it to the "pro's".. well he just got it back and it was running horribly bad like it was missing horribly. i could hear a super large vac leak and noticed this guy had actually cut his hard EGR pipe and bandaged it with heater hose that appears to immediately burned through. So i fixed that with some steel braded hydro line good for 700 degrees on the rubber side and 1300 on the braid side (inside) resolved. But while i was in there i noticed he had a new hose coming from the TB to the p/s valve cover and a PCV valve in there. stumped me simply because when i owned an LT1 i could have swore the pcv was on the D/S side of the intake mani and the positive flow actually went to a simple vent in the P/S valve cover. he is having an issue with oil coming out of the dipstick. so i took that pcv off the P/S and gutted it and stuck it back in. Did i do the right thing?

cardo0

Too much flow without the internal valving. That PCV controls flow by vacuum and at low rpm/high vacuum it reduces flow since there should be less blowby and saves idle vacuum. Once RPM increase the vacuum signal is reduced and the PCV is open internally to handle the greater blowby past the rings. It is also a check valve in the opposite direction for whatever reason.

With the PCV gutted it will be like a major vacuum leak as if the hose was connected by itself. But if he was having oil come out the dipstick means that hose is not connected to the intake vacuum or a hole in the valve cover. This is pressurizing the crankcase and will blow out all the engine oil seals.

Get the correct PCV connected to a vlv cover hole that is open and the other end to the intake.
cardo

LIQUIDZ28

I would say yes your right on this one, but this is an LT1 the valve cover has no pcv valve, the valve is supposed to be on the side of the intake manifold in the middle, drivers side. i am trying to confirm that there is not supposed to be 2 pcv valves, as my 97 only had 1 and my corvette LT1 only had 1, this one had one in both locations. which threw me for a loop. Also, the hose the valve cover is connected to has a positive flow (blows) instead of a vacuum which is also strange to me.

LIQUIDZ28

ok got my answer, there is no "valve" on the passenger valve cover, it is WOT vac only so it was supposed to just have a open elbow in there but the "mechanic" that worked on his car must have broken it off so he just stuck a pcv valve in there to replace it which made sense all the way up to its not supposed to have internals. if anyone else has any more input on the subject i would love to learn.

whytryz28

iTrader: (28)

Yeah 93's are fun to work on.

cardo0

That drawing shows the PCV connects from the intake to another port on the intake below on the same drivers side. So that tells me the intake has a passage to the lifter valley where it receives the blowby gasses.

That hose on the valve cover that is blowing at u is where the blowby crankcase gasses are trying to get out. As long as u have the PCV installed in the correct direction no reason why u cant use that for a PCV port - but the other end has to go to the intake vacuum port.

cardo

96capricemgr

iTrader: (1)

Professional often means "gets paid to do" means absolutely nothing about competence.

LIQUIDZ28

I would be hard pressed to have anyone even check my oil. IMHO if you own a sports car, you need to know her like the back of your hand. This one just stumped me as there was 2 pcv valves. Just got off the phone with the guy i sold my 97 z28 to had him check the p/s valve cover and sure as sh*t there is no pcv there, just an open elbow. I really would have rather gotten the answer from here as i diddnt want to bug the guy but wanted to have it handled before he drives home in an hour.

Fastbird93

iTrader: (10)

The 93's only have one PCV Valve, which is on the drivers side of the manifold in a big rubber grommet, and a 180* tube that connects to a port right next to the PCV itself.

The passenger valve cover to throttle body is a fresh air hose. There should be NOTHING in that line.

LIQUIDZ28

Roger that, that is exactly what i remember but needed another brain to slap to make sure. Thanks!

SS RRR

iTrader: (2)

Check the routing of the spark plug wires. The hose from the passenger VC is a breather tube, which is to remain neutral. When the car is under vacuum, it draws it's filtered/metered air through that hose, and when it's not in vacuum, blow-by is supposed to channel through that hose into the intake. Gutting the valve was the right thing to do, but if you want to be thorough, locate a grommet and fitting for the correct breather tube.

LIQUIDZ28

Fortunately, the grommet in there was a pcv valve grommet, nice and tight. also i have never seen the amount of oil he has spurting out that was there, even coated the underside of the hood. I am beginning to think the pcv was an issue, but i doubt it was the cause of the oil coming out of the dipstick and or oil cap. Under further inspection i noticed the shims on the underside of the oil cap where worn to the point where the oil cap is able to screw on to the point where the O ring was passing the seal point too far and was no longer sealing causing air to be released back into the atmosphere instead of the intake. grabbed him a new cap last night, hopefully that fixes it. its back to a perfect idle and he has his down shift sideways back. so seems to have fixed the power loss issue. Last night i made some cardboard shims to put under the cap to see if oil was coming from the cap so it would seal and the oil stopped shooting out. Thank god. also this is a 93, i'm not sure if the blow by is even metered or not.

SS RRR

iTrader: (2)

If anything it's filtered air being introduced inside the engine. The PCV valve may have stopped up the normal blow by causing excessive crankcase pressure which could mean a dipstick shooting up. Just a guess.

LIQUIDZ28

roger that, that was my initial assumption also.