Oil getting into new Cobra Upper I/T

[50canuck]

Since getting new Cobra I/T for my 86gt, i've had some idle issues and doesn't seem to make as much power as predicted. Have noticed a lot of oil in upper I/T, and #4 & #8 plugs were oily, cleaned it out and rerouted pcv vac line. next day, still oil in upper. This new cobra has different locations of vac fittings as stock 86 upper or 88 upper that i had been using. With 88 upper all vac lines went to fittings under intake, there were 3 plus the tree, i had brake boost,fuel pres, and small blake line to tree. Pcv, map & a line from air pump canister to 3 fittings under intake. With cobra , it has one fitting under intake, plus tree, and one on driver side of intake. And one on neck of intake near T/B, I've tried a couple of different combos, for the routing of the lined , but still oil in intake. Can any one with 86 gt , or 87 to 88, tell me the proper routing , or my oil is getting in intake. I wasn't having this problem with old set up. Can the oil effect the sensors? thanks for any advice

 

[HISSIN50]

oil can cause detonation if it reaches the chambers.

A catch can or air/oil separator might work for ya. I just installed one (finally) on the 94 GT and it seems to knock down some oil.

Are you forced induction? How much boost and what mods to PCV have been done to accomodate boost, if running a decent amount?

Good luck.

 

[SteveZ]

I have had a Cobra intake manifold for a year and it does the same thing. I installed the intake when the engine was rebuilt. It was bored .030 over and new forged aluminum pistons and rings installed. The car smoked on startup and smoked under hard acceleration since the rebuild. At idle and at a steady state, the smoke cleared and seemed to run clean. I initially attributed it to break-in smoke or worn valve seals or valve guides on the Thumper Performance ported cast iron heads which I purchased from a friend, but as miles started to build the engine kept smoking at startup and when accelerating hard.
I replaced the Thumper Performance ported cast iron heads with new GT40X heads. The Thumper heads were badly oil fouled on the back four cylinders. # 2 and #6 didnt look bad, and #1 and 5looked normal for an engine with 1500-2000 miles. After installation of the new GT40X heads, the car ran clean for about twenty miles and then started smoking on startup and under hard acceleration. I pulled the heads and #4 and #8 are heavily oil fouled and greasy appearing. # 3 and #7 are slightly carboned and the front four cylinders appear normal for a set of heads with 35-40 miles. I have been theorizing and seem to think that the rings are somehow the culprit in the excessive blowby in the PCV and upper intake which left a puddle of oil after I pulled it and set it on the floor. The under side of the Cobra lower intake has a baffle which seems to have a edge cut off and open to the bottom of the PCV screen. I am thinking of constructing a better baffle to slow down the introduction of oil into the main baffle. I currently have the engine at the engine shop being freshened with new rings and bearings. Any one else ever have any experience with a situation like this?

 

[sweet88gt]

Seems to be a common problem. I also had fuel and what I now found out was oil being sucked thru the intake. Ends up being a blow by problem. New heads and uncountable miles. Provide a way to catch the oil or run some type of seperator to slow the problem. Only 2 ways to look at it. 1 run a evac pump to pull a vac in the crankcase. 2 rebuild the motor and hope this solves the problem. Either way a catch can is making its way into my car.

 

[vristang]

There is no reason why a motor that is in otherwise good condition should need an oil seperator to solve this problem. Find out what is causing the oil to accumulate in the intake before buying parts that are most likely unnecessary.


I have had a similar problem with a motor I had just built. At initial startup and until I pulled the motor at about 2,000 miles it smoked constantly. I seemed to always be burning oil. I would find the dipstick pushed from its tube, sometimes hitting the hood, and oil being pumped out of the tube onto the headers. I had pulled one head to investigate and found all four chambers were caked in gooey oil. When I did a leakdown test on the other head, I had 20% leakdown. A normal motor is supposed to get less than 10%, even after a few years of life. Turns out that my stroker kit had come with low tension rings. Blow by was the culprit. Be very specific about what rings you want to buy.

Other things that can cause similar problems are removed baffles (both at the valve cover filler neck and the PCV), and a non functional PCV. If you have removed the valve cover baffle for rocker clearance, then you have to install another baffle. I have done this and could put up pictures if any one cares.

Hope you find the problem, Good Luck

 

[sweet88gt]

I am intrested in the pics for the added baffle. As far as the info I provided it seems in my case to be the culprit of blow by in a otherwise worn motor. I guess I should have said that. I try to only post when I have dealt with the same problems most of which have been recently. But I am still learning and the curve is large. I believe the original post didnt say much about a rebuilt engine and was focused on his post.Sorry for the confusion.

 

[vristang]

I am intrested in the pics for the added baffle. As far as the info I provided it seems in my case to be the culprit of blow by in a otherwise worn motor. I guess I should have said that. I try to only post when I have dealt with the same problems most of which have been recently. But I am still learning and the curve is large. I believe the original post didnt say much about a rebuilt engine and was focused on his post.Sorry for the confusion.

I have them on CD and that drive isn't working. Basically what I did was take a thin sheet of Al. and bond it in place with some JB Weld. Take your time and think about how the oil will flow into the filler neck. Make sure you scuff all bonding surfaces extremely well and get all the oil off the metals.

I will keep trying to get the pics, but I am not having any luck right now.

 

[50canuck]

oil in upper I/T

I am using a oil seperation system for the pcv vac line, and I'm trying a filtred oil filler cap,and disconnecting the hose from oil filler to T/B. Then will check for oil in I/T, the oil sep, is catching oil, so i assume it must be from oil filler line to T/B. I'f it is a poor baffle in lower of these cobra,s, then I guess I can try and modify it. thanks for replys

 

[ninety15.0]

Whats that filler neck to TB hose doing supposedly? what's its purpose? I have been wondering for a while what to do with it when i drop my motor in...

 

[HISSIN50]

I am using a oil seperation system for the pcv vac line, and I'm trying a filtred oil filler cap,and disconnecting the hose from oil filler to T/B. Then will check for oil in I/T, the oil sep, is catching oil, so i assume it must be from oil filler line to T/B. I'f it is a poor baffle in lower of these cobra,s, then I guess I can try and modify it. thanks for replys

As I am sure you know, you kind of defeated the purpose of having a PCV in the first place. If you are running any breather of any sort (unmetered air), you could just run a breather or 10 on valve covers, etc.

Good luck.

 

[vristang]

Whats that filler neck to TB hose doing supposedly? what's its purpose? I have been wondering for a while what to do with it when i drop my motor in...

That hose vents crankcase pressure to the intake so that the oil vapors are burned, instead of going into the atmosphere.

Too many people (in my opinion) remove this hose when they start finding oil in the intake. The correct answer is to find the reason for excessive crankcase pressure. Removing the tube is a band-aid at best.

As an example, if I had done the knee-jerk solution (cap the filler hose, install an oil seperator, and remove the PCV) I never would have found out that the motor had 20% leakdown. To give you an idea of how bad that is, my static CR is 8.85, and when factoring in all that blow-by the effective CR is 7.08. No wonder the motor never seemed to run right.

Find the real problem!

 

[HISSIN50]

Whats that filler neck to TB hose doing supposedly? what's its purpose? I have been wondering for a while what to do with it when i drop my motor in...

I am going to respectfully disagree with the above-statement.

The TB to oil filler hose is to allow crankcase flow to be bi-directional. In the old days we ran breathers (bi-directional). With a PCV valve, the valve is a check-valve. There needs to be a way to introduce air flow the other way when conditions require it. The TB to oil filler hose allows this - and be it with metered air (on a SD set-up, one could run a breather on the Oil filler bung, for off road purposes, of course since metered air is not an issue).

 

[vristang]

I am going to respectfully disagree with the above-statement.

The TB to oil filler hose is to allow crankcase flow to be bi-directional. In the old days we ran breathers (bi-directional). With a PCV valve, the valve is a check-valve. There needs to be a way to introduce air flow the other way when conditions require it. The TB to oil filler hose allows this - and be it with metered air (on a SD set-up, one could run a breather on the Oil filler bung, for off road purposes, of course since metered air is not an issue).

Boy am I confused. Please help me to understand this.

Why would you want to run fresh air into the crank case? For that matter why would you want to run any air (fresh or otherwise) into the crank case? There is already a constant supply of air from blowby.

Here is how I understand it. Blowby pressurizes the crankcase. The pressurized air increases the chance of gasket and seal failure, and increases aero drag on the crank. I thought this was the reason some extreme motors run vac pumps on the crankcase. The PCV is supposed to let the crankcase pressure vent, but close off in the event of a backfire so that crankcase fumes will not be ignited. Backfires would not be much of an issue for the filler neck tube since it is outside the Throttle Body, so it does not require a one way valve.

Under what conditions do you want airflow into the crankcase?

I hope I have not offended you HISSIN50, I just wish to understand this better.

 

[HISSIN50]

Boy am I confused. Please help me to understand this.

Why would you want to run fresh air into the crank case? For that matter why would you want to run any air (fresh or otherwise) into the crank case? There is already a constant supply of air from blowby.

Here is how I understand it. Blowby pressurizes the crankcase. The pressurized air increases the chance of gasket and seal failure, and increases aero drag on the crank. I thought this was the reason some extreme motors run vac pumps on the crankcase. The PCV is supposed to let the crankcase pressure vent, but close off in the event of a backfire so that crankcase fumes will not be ignited. Backfires would not be much of an issue for the filler neck tube since it is outside the Throttle Body, so it does not require a one way valve.

Under what conditions do you want airflow into the crankcase?

I hope I have not offended you HISSIN50, I just wish to understand this better.

There is not quite always a steady supply of blowby into the crankcase. One does not want a vacuum actually pulled inside the crankcase (during these infrequent times) and this secondary hose (TB to oil filler) keeps things closer to equilibrium.
And under zero-manifold-vac situations, the TB to oil filler hose acts as an additional vent.

But the hose is still there for bi-directionality. As you noted, often people delete that hose as a band aid. Often the PCV screen/valve, etc are clogged (or the system is simply overwhelmed with blowby), so that single TB-to-Oil filler-hose tries to do all the venting, which overwhelms it and allows a decent amount of oil into the TB. So by deleting that hose (depending upon how it is done), can overwhelm the crankcase ventillation even more.

I am not even sure we are disagreeing - we just have different takes on the primary reason for that secondary hose. No offense at all taken - we are all here to post and see peoples' opinions as a means to broaden our own (you guys have changed my takes on more than a few things), even if we don't exactly agree word for word (as long as we understand how the systems work and can troubleshoot them, the rest is semantics).

Maybe you can help me: if that secondary hose is to allow vapors to be burned, why is it there? The PCV valve's hose (which injects vapor into the upper intake in most cases) already does that. If they needed a bigger vent (bigger PCV valve, etc) then they would do that rather than use a secondary hose, which happens to not have a check valve. It just seems to me that it is for allowing air to flow bi-directionally.

 

[SteveZ]

I agree with VRISTANG, there is a problem with my engine, and it isn't the PCV. I think it is probably a ring issue.
Either the rings didn't seat, for whatever reason, the ring end gap was too large, or the rings were incorrectly installed/broken. Whatever the reason, I have taken the shortblock to a reputable rebuilder and am currently waiting his diagnosis of the problem and freshening of the shortblock.
I am also going to install a secondary baffle under the lower intake and stop any chance of oil splash being vacuumed past the PCV.

 

[vristang]

There is not quite always a steady supply of blowby into the crankcase. One does not want a vacuum actually pulled inside the crankcase (during these infrequent times) and this secondary hose (TB to oil filler) keeps things closer to equilibrium.
And under zero-manifold-vac situations, the TB to oil filler hose acts as an additional vent.

But the hose is still there for bi-directionality. As you noted, often people delete that hose as a band aid. Often the PCV screen/valve, etc are clogged (or the system is simply overwhelmed with blowby), so that single TB-to-Oil filler-hose tries to do all the venting, which overwhelms it and allows a decent amount of oil into the TB. So by deleting that hose (depending upon how it is done), can overwhelm the crankcase ventillation even more.

I am not even sure we are disagreeing - we just have different takes on the primary reason for that secondary hose. No offense at all taken - we are all here to post and see peoples' opinions as a means to broaden our own (you guys have changed my takes on more than a few things), even if we don't exactly agree word for word (as long as we understand how the systems work and can troubleshoot them, the rest is semantics).

Maybe you can help me: if that secondary hose is to allow vapors to be burned, why is it there? The PCV valve's hose (which injects vapor into the upper intake in most cases) already does that. If they needed a bigger vent (bigger PCV valve, etc) then they would do that rather than use a secondary hose, which happens to not have a check valve. It just seems to me that it is for allowing air to flow bi-directionally.

Thank you for replying. Too often when I question someone they disappear. Makes it tough to expand your understanding. I guess we don't disagree.

I will have to think it over today though as I am a little distracted here at work.

 

[HISSIN50]

Thank you for replying. Too often when I question someone they disappear. Makes it tough to expand your understanding. I guess we don't disagree.

I will have to think it over today though as I am a little distracted here at work.

No biggie. I try and reply to anyone who asks something specifically to me, but I post often and simply miss some threads or replies (if I ever miss something, feel free to PM). I also enjoy looking at things from different people's perspectives, esp smart folks like yourself.

And you helped Steve Z (who agreed with you, which is good because nothing I said was directly related to his interjection on the thread). But seriously that is cool that you helped him out.

 

[vristang]

No biggie. I try and reply to anyone who asks something specifically to me, but I post often and simply miss some threads or replies (if I ever miss something, feel free to PM). I also enjoy looking at things from different people's perspectives, esp smart folks like yourself.

And you helped Steve Z (who agreed with you, which is good because nothing I said was directly related to his interjection on the thread). But seriously that is cool that you helped him out.

Oh stop, you're making me feel all tingly inside. Seriously thanks for the praise. At least my misfortune could help someone else. It sure wasn't as easy for me to find the source of my oil control issues as I made it sound. Maybe my experience can help SteveZ solve his problems quicker.

HISSIN50 I see your point about the redundancy of the secondary TB vent line. I don't understand the need for it unless there was a need to bring fresh intake air into the crankcase.

I guess I will have to hit the books again on this because I can't think of a situation where dragging intake air into the crankcase would be beneficial.

And I thought I was done studying cars when I left school! I guess knowledge really is a journey, and not a destination.

 

[txstang84]

you guys are just too nice-so i should watch out for oil in my intake since i'll be running a cobra when my 331 goes in...1EVIL88VERT also has had problems with that one, when we pulled the upper intake the back four runners were all wet with fresh oil, the hose from the pcv to the plenum was full, and the plenum itself had a more than fair amount of oil in it...we've tried more than one remedy with this one...

i'm seriously thinking about rerouting the hose from the pcv valve to a different location on the intake hoping that maybe that will slow the pull of oil coming from the lifter valley....hopefully

 

[GREG91GT]

I have the same problem with my systemax intake, so i put a clear fuel filter in the vacum hose between the pcv and the intake and i also run a push in breather in my valve cover.