Here is what I know:
The symptoms are that it runs really rough at any RPM, but better the higher you are. Idles like it's shaking the car apart.
New plugs foul up within 5 minutes of run time, maybe less.
I did a power balance test and all the cylinders were firing, but when I did it the car jumped up to about 3k rpm idle and I had white smoke out the tail pipe and quite a bit coming off the engine as well.
Some misfiring, not as much but still some there.
Bogs hard with a slight touch on the throttle.
So much gas in the oil it's "milkshaking" it. (it's not coolant, my coolant level holds steady and I pressure checked it).

Things I have done or checked:
Checked for leakage at the orings by hooking up the fuel rail and pressurizing it before I reinstalled the plenum, no leakage that I could see.
Injectors have been flow tested and they all ohm out between 12.5 and 12.7 ohms.
I pressurized the coolant system at the radiator today, it held 10psi steady with less than a .2psi drop after 5 minutes of being pressurized.
I had a fuel pressure tester hooked up while I was experimenting today, it showed the pressure holding steady between 45 and 47ish PSI.
New coolant temp sensor
New fuel pressure regulator and dampener

My remaining two "long shot" ideas.

When I redid the exhaust valve covers I got some liquid gasket on the cam lobes.
Somehow related to doing the coolant bypass.

This all started after doing a plenum pull to replace the injectors and redo my valve cover gaskets. It's been almost two months, I'm kind of going insane. Everything "ran" before I did the pull as well.

 

I can tell you from Experience, that Excess gas in the Oil WILL NOT MILKSHAKE. It will make a Very thin Oil that will BURN..

If you have a Milkshake, you have water in the Oil.. I do not know how it's happening, but it is..

Thinking if it's not the 'Bypass Tubes' for the T-Bodies, hooked up improperly, then it's the Lower Intake Manifold Coolant Crossover Passages are leaking at the Intake Gaskett..

Cap

 

It is a non-turbo. I pulled the bypass lines and only coolant was in them, no oil. The car has had the plenum put back on three times during the process of trying to figure this out, if it was a simple issue of rebuilding then I would think it would have been fixed by sheer chance by now.

Any suggestions on how I can check the second water access point you mentioned? This is a problem that only manifested after I took it apart, seems like anything at the lower intake manifold should be untouched.

I undid the bypass, re assembled the under plenum cooling hardware, and I had the coolant lines run correctly. You're sure it's only water that can cause the milkshake thing?

 

There is the Possibility that what you are working on, was already broken before you started..

Case in point.. the 300 Im REBUILDING now.. Started off as a Bad water hose behind the Intake.. Ended up oil in the water.. ( not the other way ) and that lead to complete engine removal, and Well.. it gets worse..

Complete tear down.. Two bad headgaskets.. two cracked heads.. The Z-Guy in town, sold me old style heads for my 95, and did not say a thing about the Intake Differences.. ( Like I knew the Difference? )..

After a grand on Valve Work.. and 600 for a Bore and Pistons, I find out during the Assembly, that the heads are wrong.. Well im a little deep into this project to stop now.. so a few hours of port matching, and I'm still purchasing parts, and hanging them on the Block..

Back to your Problem..

Milky oil is water in the Oil.. Period.. If you are absolutely sure it's not your hoses somehow hooked to the Intake Vaccume, then it's not.. and your problem is somewhere else.. But if you do not have an oil cooler of any type, then the water in the oil is likely a bad head or gasket, r in my case.. both..

Likely in my case the Head gaskett seeped oil into the water passage ways, and turned the Water/Oil to Peanut-butter.. that prevented the cooling, and the heads were toast in a few minutes.. It was during a mountain run.. fun but expensive..

Cap

 

Well, I decided I was going to just cap the lines off as various guides suggest instead of running the bypass, we will see how that goes. I doubt it has any effect because I'm 95% sure they were run correctly.

I drove the car around for a month after I bought it, before I discovered my injectors ohming out in the 18's and decided to take it apart. Was running good, the oil came out black and nasty when I changed it, no weird fluids in it.

I did pretty much every test outside a leak down that I can think of to test the head gasket's integrity. Compression test was great, and the cooling system holds pressure when pumped up to 10psi. A leak down test won't work until I resolve the problem, for reasons I'll explain(I think, feel free to correct me on anything).

I've been thinking about it and I'm not entirely sure "milkshake" describes what I'm seeing. The oil does not look like peanut butter, it is just super thin and a really nasty off white color, also it smells strongly of gas which is why I originally believed it to be gas. If a significant amount of gas in the oil would not cause that problem then it's water and I need to figure out what's wrong with it.

The leak down test will not work right now because the oil is so crapped out that it's not sealing the piston rings against the cylinders correctly. I did a leakdown test and every cylinder was 30% with air shooting out my oil fill cap. (again, no radiator bubbles leading me away from a head gasket)

Here is the theory I'm working with at the moment:

I had a leaking o-ring the first time I did this process, and it dumped a shitload of gas into my oil. I fixed the o-ring (checked before reassembling this time, and verified again with a fuel pressure tester that I bought specifically for this) but my oil is still all gunked up, cylinders are not holding pressure correctly because of the aforementioned oil problem, with the possibility that the sealing issues and combustible () oil, caused by the original o-ring problem are causing the symptoms I am seeing now.

You're a lot more knowledgeable about this than I am, what do you think? I am waiting on a helicoil set to come in the mail before I put it back together. (whoever owned it before me stripped out 3/3 bolt holes that connect the driver side part of the balance bar to the plenum, sigh) So I'm open to doing any tests you can think of, and brainstorming lol. If this does not work I think I am going to take it to the dealer and probably end up giving them my savings to fix it... sigh.

 

You are already two elbows deep into this thing.. why stop now..

I'd get the oil out.. change it with cheep dino oil.. and keep checking things..

IF the oil has gas in it, you do not want to run it in the engine..

1) It will not lubricate properly, and will screw up the internals
2) It MIGHT catch fire..

So get the oil out..

I'm not thinking the Oil will have a Big Impact on the Leak down test..

The loner you work on the car, the more comfortable you will be with all of the guts, and what they do.. AND if you take the car to a shop, you are paying them to learn about your car.. UNLESS thay know Z's inside and out..

Pull the Dipstick.. take it away from the Car, and see if the Oil on the end will Lite off like BBQ Starter Fluid.. If it lites and burns, it's got gas in it.. as reqular oil needs to be REALLY hot to burn, or be 'Wicking' aginst something to provide temps for combustion..

Cap

 

Well, I would not call it BBQ fluid (I have changed the oil once, it's relatively good looking oil now, not the creamy stuff I had before) but one try the bottom of the dipstick caught fire long enough to pop and look like a miniature set of black cat fireworks, the second time (after putting it back in the dipstick tube) it did not catch at all though.

I am very sympathetic to the point of view that taking it to the dealer is paying them to learn about my car, especially considering a major reason I started this project was to learn more about my car, kind of at my wits end though.

 

Hostory Please..

The Car WAS running good untill the intake came off?.. is that right..

Has the car ever run good for you?..

Cap

 

Yeah car was running ok before I took it apart, it needed new injectors but it was running. I took it apart and did the following:

Coolant bypass
New injectors
New valve cover gaskets all around
Replaced all the rubber I could find that was brittle or worn

 

I sent you my Cell Number in a PM..

A Conventional Compression test will give a general health of the engine.. I'm not going to bieleve the Goo on the Cam Lobe has anything to do with this..

Did it ever run good for you?..

Cap

 

Did the fuel system pressure test, not holding pressure at all. Took some pictures to make sure I hooked it up right, I put the pressure gauge right on the fuel rail itself in between it and the second dampener (the one on the passenger side).

ImageShack® - Online Photo and Video Hosting
ImageShack® - Online Photo and Video Hosting

 

Something does not look right with the fuel in/out on the regulators..

See if you can find a picture.. else I can look at mine when I get home..

Is the In and Out Reversed on the Regulators?..

Cap

 

Took a video for more detail:

http://youtu.be/ZndI07AMLSA

 

I made it a little more accurate and slightly less ghetto and installed the pressure gauge at the junction between the two halves of the rail. The system still won't pressurize. I discovered if I crank it over to the "on" position it will basically put another 10psi into the system, but it regardless loses all it's pressure within a few minutes. No leaking from the o-rings though, no idea why it's not holding pressure.

 

Ok, oddly enough I got it to hold 25psi steady *once* then when I tried to turn the key over to "on" once more to hopefully pressurize it 10psi more to double check for o-ring leaks it dropped back down to 0psi.

 

I looked at the Regulators on the Z here.. Same hook up as yours..

Could have a Bad Check Valve in the Fuel Pump.. Or the Pump could be bad..

Should be able to get more than 25 PSI..

Cap