Oil In Intake

prgt347

Active Member
Jan 16, 2009
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#1
Oil is being sucked into the upper intake manifold from the PCV valve, causing the engine to blow out blue/gray smoke upon startup and heavy acceleration.

92 GT
347 Stroker
Edelbrock Performer Intake
Roush Iron Heads
High volume oil pump
All stock emissions gear attached and working except running O/R H-pipe with no cats

Built the stroker motor about 15 years ago and always had more oil consumption than with the stock motor. Being a 347 I expected a little more consumption and didn't worry about it, just kept the pan full. Haven't driven it much over the past 5 years but it always ran strong, just smoked a little upon startup and heavy acceleration and leaked some oil. Been getting it back into top shape and started fixing all the areas oil was leaking; valve covers were the main problem but also had a little oil around the PCV location. Checked everything - the PCV valve was fine but didn't fit properly in the grommet and the mesh screen below was missing. Installed a new screen, proper sized grommet, new PCV, and new hose to upper intake. Also during this time I replaced several vacuum hoses that had gotten loose over the years. Good news is that it no longer leaks oil. Bad news is that it now burns oil like crazy.

Traced the problem back to the PCV location. Oil is being sucked into the intake from the PCV, pulled into the back 4 intake runners, fouling plugs #3,4,7&8, creating the smoke, and making me really mad.

I've been reading through the forums for ideas and found two threads that seem to contain the most pertinent information.

I tried the method of splitting the hose for two PCVs before bringing into the intake, to hopefully slow down the amount of oil getting to the top (see link below, has pictures) but unfortunately it didn't seem to make any difference.

https://www.stangnet.com/mustang-fo...ke-via-pcv-solved-really.886733/#post-8924767

As a test I left the dual PCV contraption on but removed the line going to the intake. I capped the intake hose but left the hose going to the PCVs open. Started it up and no smoke. Drove it hard, revved it up, etc., and no smoke. No oil is coming out of the open hose either. Car is running better than ever with no oil leaking and no smoke at all. Haven't pulled the plenum to confirm no oil and only checked #8 plug, which was now a nice tan color. However, with the hose to the PCV left open I don't see this as a permanent fix.

Read another thread (see link below) that suggested running a relief hose from the driver's side valve cover to the PCV / intake hose to reduce the amount of pressure to the PCV and still pull out crankcase gases. Sounds like a valid option but before digging through eBay for valve covers or cutting into mine (yikes), I would like more input.

https://www.stangnet.com/mustang-forums/threads/oil-in-upper-intake-from-pcv-hose.701999/

I have not run a compression test yet but by the way it drives with the hose off, it feels 100% with no misses, no hiccups, nothing...idle is even excellent. Hoping for a simple solution to fix this for good.
 
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#2
On one side of the valve cover run a breather. Then on your other side leave it alone. What's happening is it is pulling crank case gas faster than normal, so to counteract this and relieve pressure all you need to do is put a breather on one valve cover. I had the same problem on multiple engines and this was the way I had fixed it
 

Noobz347

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#3
The problem with a "breather" is that you effectively kill the PCV system.

A one way check valve would at least preserve some function.
 

prgt347

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Jan 16, 2009
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#4
Thanks for the replies. From what I’ve read and understand about PCV systems using a breather is a no-no as it eliminates the recirculation of gases back into the engine.

Noobz, please elaborate on your post...by check valve do you mean PCV? What are your thoughts on installing a second PCV in the driver side valve cover and tying it to the main PCV and intake vacuum?
 

Noobz347

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#5
Thanks for the replies. From what I’ve read and understand about PCV systems using a breather is a no-no as it eliminates the recirculation of gases back into the engine.

Noobz, please elaborate on your post...by check valve do you mean PCV? What are your thoughts on installing a second PCV in the driver side valve cover and tying it to the main PCV and intake vacuum?
Something along these lines:

http://www.jegs.com/i/Ford-Racing/3...MIqPTSrbqv2AIVVZV-Ch1BpwC_EAkYBiABEgJAivD_BwE

...and I whole heartedly support adding a second PCV and vacuum source. That will effectively double your flow volume, slow the air in the PCV system, and reduce the amount of oil picked up in the flow.

It will not however, make up for poor ring seal or excessive blow-by.
 

prgt347

Active Member
Jan 16, 2009
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#6
So are you suggesting installing this type of part in the driver side valve cover? Then connecting it to the PCV tubing going to the intake?

Or installing it in another location? Seems I need to leave the passenger side valve cover like it is (stock) so that it doesn’t affect the air going into the throttle body...
 

prgt347

Active Member
Jan 16, 2009
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#7
While trying to decide which way to go I noticed there is no baffle under the PCV screen in my lower intake. Before cutting into the valve cover I'm probably going to install a baffle and see if that eliminates the problem first. Anyone have suggestions for a baffle on an Edelbrock Performer RPM?
 

Dan02gt

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Mar 2, 2003
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#8
Years ago my dad and myself built a little 306 for his 91 GT. The car had GT40 heads and a Chinese Cobra intake. It smoked quite a bit so we thought it was a problem with the short block. So we took the car to the machine shop that did the work on the block and they diagnosed it as pulling tons of oil through the PCV system. They did what you are talking about to fix it. They capped off the PCV in the lower intake and drilled the driver's side valve cover and installed the PCV valve there. I can't say it 100% stopped any oil from being pulled but it greatly reduced it and the car didn't smoke anymore.
 

Noobz347

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#9
So are you suggesting installing this type of part in the driver side valve cover? Then connecting it to the PCV tubing going to the intake?

Or installing it in another location? Seems I need to leave the passenger side valve cover like it is (stock) so that it doesn’t affect the air going into the throttle body...

That air has already been metered. The mistake (if using a closed PCV system) is allowing that air to escape out of anywhere that is not the exhaust.
 

prgt347

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Jan 16, 2009
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#10
Went ahead and drilled into my driver side valve cover over the weekend. Installed some sort of pressure fitting (Home Depot) that screwed into the hole I cut, stuck in a PCV grommet, and a PCV valve. See attached pics. I first tried a T set up, connecting the PCV behind the intake and the new PCV on the valve cover to the manifold vacuum. Still smoked and had a lot of oil in the intake and coming out of the exhaust; I'd say it was less than before but still way too much. Plugged the PCV behind the intake and ran the new PCV straight to the intake vacuum - no more smoke or oil coming out of the exhaust. I only drove it a short distance but no smoking at any point driving, idling, or revving. I haven't opened the intake plenum yet but don't expect to see any oil now. Also need to see how the plugs are looking and run some other tests to see if this will fix the problem, at least for now.

I still think the lack of an oil baffle is a major factor in the oil coming from the stock location. Plan is to buy/build a baffle and see I can reactivate the stock location and possibly run both PCVs together.

I'll put more miles on it and reply back with updates. Thanks for your comments.
 

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7991LXnSHO

5 Year Member
Sep 1, 2010
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#11
The Ford intakes have a large baffle under the intake. I am not near an extra one right now, but I am fairly sure they are for oil control on the way to the pvc valve. Some are big enough to help as a heat shield, but as they are not full "turkey basting pans", I doubt that's a main purpose.
If your Edelbrock intake has no baffle, that's a problem.

Please do a leak down test and compression check. You may have more blowby than a regular system can possibly handle.

As far as a breather, some of the early systems pulled filtered air out of the round, carrbureator top filter housing, into one valve cover, (through the engine), out of the other valve cover where the PCV valve was, then under the carb.
I would probably not want an open filter on one valve cover in an EFI car as it could act like a big vacuum leak and tick off your computer. What if it pulled air from somewhere between the air meter and TB to the first valve cover?
 

monte87

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#12
Do not run a breather on V.C on a non S.C. fuel injected 5.0. You will allow unmetered air into the system, giving you a surging erratic idle. "No good". If anything run a small oil separator, it will prevent oil from going into intake. Plus, make sure the baffle is still under the passenger side valve cover.

Hope this helps
Anthony
 

mikestang63

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Aug 27, 2012
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#13
You either run a
  • closed PCV system with a good TBird PCV or check valve
  • remove the PCV and run breathers to catch cans

Not both
 

prgt347

Active Member
Jan 16, 2009
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#14
Just to follow up...I am still running the closed system through the newly created PCV in the driver side valve cover, with the stock PCV location blocked off. I've put at least 500 miles on the car since doing this and so far everything is working perfectly. No smoke, ever. Oil level is staying full and has nice color. Plugs are all clean. No oil in the intake. I'll still need to install a baffle one of these days but until then this seems to have fixed my issue. Nice to be able to enjoy driving it again. Thanks again for your comments.
 

billison

I like tinted tail
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Feb 27, 2006
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#15
Dunno if this was covered. But do you have the tube from the oil till to the throttle body? Mine was capped and replacing that and adding the mesh filter fixed it.
 

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