Problem with PCV system ?

[vanvan2801]

Hello everyone !

My 1991 ZR-1 with a 1990 engine tends to smoke oil. I know the 1990's don't have an exhaust seal so they tend to smoke when starting up, I also know that oil can build up in the plenum when driving at low rpm, and as soon as you accelerate the oil is sucked in and burns and causes smoke. but my Z smokes almost constantly, in slow motion she doesn?t smoke. but when accelerating it smokes blue. she doesn't smoke a lot but too much for me. ever since I have she has always smoked that way. I changed the injector housing gaskets a few months ago, I also changed the hose with the dual PCV valve. but a lot of oil (I think) is building up in my PCV system.
After 60 miles the hose with the dual PCV is "filled" with oil (see photos) I can also see a lot of oil in my injector housing (see photo) I tried to unplug the system to see if that was changing something..i just speeded up a few times for about ten minutes, but she was still smoking. (I disconnected the vacuum line from the PCV system, the 2 grommets and the ducts connected to the cam cover. I noticed that the filters on the cam cover were decomposed or even absent on one side. I plan to replace them. but I don't really understand their goals? for information, the engine has 80k miles, with the secondaries removed, a Haibeck chip, 16 new injectors, coils, etc. it does not have cats (obx headers) and the car runs very well . the compression test is very good, and all spark plugs have normal color (not oily).
in my opinion the problem is with the PCV system compared to the oil that I find in the system.

I hope you can help me, I may be paranoid and that is quite normal for a 1990 LT5 of smoking oil (blue smoke and smell of oil)
thanks in advance for your answers.
Greeting from Belgium 🇧🇪

[Ccmano]

It's not your PCV system. Even our own Mark Haibeck has shown that the PCV system contributes little to oil issues in the intake. What is much more likely in this case is that your lower injector housing gaskets are leaking oil into the intake. I have seen this on numerous engines including my own. Loose injector housing bolts have long been a known issue. Combined with age and heat cycling the lower IH gaskets shrink and become brittle allowing oil to be sucked in from the crankcase. Because of this oil is drawn more forcefully into the injector housings then straight into the intake side of the heads. Before I learned this I was convinced I had ring or valve guide issues. This requires a plenum pull but it's not a difficult job.
H
:cheers:

[vanvan2801]

I changed my injectors housing gaskets, would it surprise me if both were already bad? it should smoke more on one side than the other as there is little chance that both are bad. I still have the original exhaust line so I think the left and right side exhaust gas mixes? in a few weeks i will be installing my Corsa line, the pipes are well separated all along the exhaust line, maybe I will see that it is smoking on one side and not on the other which could mean that a IH seals are not good .... I hope I made myself understood? :mrgreen::mrgreen::mrgreen:

how badly did a 1990 ZR-1 smoke? just at startup?
Thank you for your answer ! :cheers:

[Ccmano]

I changed my injectors housing gaskets, would it surprise me if both were already bad? it should smoke more on one side than the other as there is little chance that both are bad. I still have the original exhaust line so I think the left and right side exhaust gas mixes? in a few weeks i will be installing my Corsa line, the pipes are well separated all along the exhaust line, maybe I will see that it is smoking on one side and not on the other which could mean that a IH seals are not good .... I hope I made myself understood? :mrgreen::mrgreen::mrgreen:

how badly did a 1990 ZR-1 smoke? just at startup?
Thank you for your answer ! :cheers:

No worries your good. To be clear, you say you changed out the lower injector housing gaskets, the ones between the injector housings and the heads, 3 months ago? Do I understand that correctly? If so the problem is elsewhere.

Mine started smoking first on startup, then also on acceleration and finally it would smoke simply sitting at idle. It all happened in about a 3 month period.
H
:cheers:

[vanvan2801]

Yes, you understood well. the gaskets between the IH and the cylinder head were changed 3 months ago, sorry my english is not very good.
mine smokes lightly when starting (5 seconds) then under acceleration always and at idle from time to time...
I found a video on YouTube of a 1990 ZR-1 (not mine) but she smokes like this : https://youtu.be/6xr2rkCQgp4 and like this at start up https://youtu.be/JrulW0XEWGY and this 1993: https://youtu.be/8Y4Re5TqIw4 also when he starts to accelerate and when he lets go of the accelerator

[Corvette95]

It took me three plenum pulls between drives to re torqueof all the top end bolts including IH to keep the torque constant after full gasket replacement. It is contrary to the book, but next time, I will use loc-tite on the IH and Plenum.

[GOLDCYLON]

It's not your PCV system. Even our own Mark Haibeck has shown that the PCV system contributes little to oil issues in the intake. What is much more likely in this case is that your lower injector housing gaskets are leaking oil into the intake. I have seen this on numerous engines including my own. Loose injector housing bolts have long been a known issue. Combined with age and heat cycling the lower IH gaskets shrink and become brittle allowing oil to be sucked in from the crankcase. Because of this oil is drawn more forcefully into the injector housings then straight into the intake side of the heads. Before I learned this I was convinced I had ring or valve guide issues. This requires a plenum pull but it's not a difficult job.
H
:cheers:

Hans is dead on with his suggestion :thumbsup:but since you said you changed out the gaskets hmmmm....

He went through this before. As described this is exactly what happens !!!!! :cheers:

How many miles are on your ZR-1 ?

[vanvan2801]

I will look at the tightening torque, when changing it 3 months ago the IH screws were tight.
the engine has 80k miles.
Do you find it normal to have accumulated so much oil in the PCV system after just 60 miles? knowing that before reassembly, I cleaned the whole system?

I spoke with a friend who also told me that not having a converter catalyst could also cause more smoke

[A26B]

I noticed that the filters on the cam cover were decomposed or even absent on one side. I plan to replace them. but I don't really understand their goals?

The filters inside the Cam Covers are there to coalesce oil vapor from the crankcase and keep it out of the intake system. Filtered air from The Throttle Body Air Horn enters the Cam Cover into the Filter. The primary purpose is to provide purge air into the engine so the PCV system will operate properly. If the PCV System was not able to deal with a large amount of crankcase pressure, the Cam Cover vents would also allow excess pressure to escape (into the intake).

If you haven't already done so, remove both PCV Valves, rinse thoroughly in solvent. You should hear the valve rattle when shaken. Air should flow only one direction, from bottom to top.

I recommend a compression check. Low compression could indicate ring wear resulting in blow-by creating excessive crankcase pressure.

[Tony Davila]

You need to buy or build yourself an oil catch can. The above mention remedies are correct but you should also include this into your solution. I built and installed two catch cans for my Z and it does catch the oil from entering the intake. That being said the LT5 will still burn oil no matter what, but we can help it burn less.

[Ccmano]

If you haven't already done so, remove both PCV Valves, rinse thoroughly in solvent. You should hear the valve rattle when shaken. Air should flow only one direction, from bottom to top.

I recommend a compression check. Low compression could indicate ring wear resulting in blow-by creating excessive crankcase pressure.

These would be my next steps as well. A quick indicator if excessive blow-by is to run the engine at idle and remove the oil filler cap. If you can feel or see air puffing out of the valve cover opening its time to conduct compression and leak down test.
H
:cheers:

[vanvan2801]

thank you all for your recommendations !
I just checked to see if air is escaping from the filler cap, and good news, it is not blowing air. on the contrary, I feel a slight depression when I put my hand.

the cam cover filters are completely broken down. can you tell me what materials i can use to replace them? I know Jerry has them, but unfortunately I am from Belgium and the delivery is expensive to my house.
I will also be looking to install an oil collector. how to make one myself ?

thank you very much for your reaction ! :cheers:

[PhillipsLT5]

Not a DIY but Jerry or
http://www.zr1specialist.com/HAT%20Web/products/cam%20cover%20filter.htm