Burning oil but need help finding the source!

[jdl902]

I re-installed the oil pan and tightened my filter adapter this spring and thought I had said goodbye to my last oil leak but now that there are no puddles under the car it's obvious the oil missing from the dipstick is going out the pipes! I'm burning enough to see it in the mirror but it's only visible on the passenger side. Looking at the plugs, cylinders 2 and 4 are definitely the worst but I'm not sure these are the only two seeing oil. There was also oil on the washers of many of the plugs (plug pics at bottom).

Setup: 5.0 with dual plane Edelbrock intake and Trickflow Twisted Wedge heads. Less than 2,000 miles on everything since new.

A bit more about the symptoms: Smoke is only visible on the passenger side when under high load, i.e. accelerating medium-hard or more. I don't see anything when I first start the engine or when decelerating.

What I've done:
1. Said "oh shit I need new rings".
2. Compression test with WOT and engine warm says the rings are fine: average 150 psi (+3psi / -5psi) after 5 cycles.
3. Blamed the PCV system; so I plugged the port on the "carb" and installed a breather in the PCV port. Now I have two breathers but still have smoke.
4 Blamed a leak in the intake sucking in oil; so I put a vacuum gauge on the dipstick and ran with the valve covers sealed. Measured positive crankcase pressure at idle so the intake isn't leaking?
5. As an extra check I drove around with the both the PCV and 2-breather setup and the only time crankcase pressure wasn't zero was on hard acceleration, it would hit 1.5 psi. This doesn't seem too high, not that I've ever checked on a healthy engine, to indicate excessive blow-by.

So I'm left baffled; it doesn't seem to be the guides since I don't see smoke on start-up or decel, It doesn't seem to be the rings since compression looks good. I think I eliminated the PCV as a suspect since I disconnected it and installed a second breather. Finally it doesn't look like it's the intake since I have positive crankcase pressure at max manifold vacuum.

What am I missing? Any ideas on what to check next? I don't see how a ring problem could get past the compression check so I'm most suspicious of the heads or intake but am scratching my head on how to check this out further.

Thanks in advance,
Jason

[snapperlr]

Really need to do a leak down test. If it's a problem with rings or that head you will find it.

[Greg_M]

You have 2 compression rings and one oil control ring. Maybe the compression is good because the top rings are OK but the oil control ring is messed up. I've never checked blow-by measuring an essentially open (PCV and breathers) but to me 1.5 seems high. What's the history with the engine? Crate, rebuilt, donor, etc...

Greg

[Venom_Injected]

Valve seals ?

[Greg_M]

Could be but valve seals produce oil smoke on startup and after taking off from a prolonged period of idling. They will definitely cause oil loss over time even if they leak just enough to not smoke visibly.

It might be worth a look under the cover and even pull the springs on #4 and #2 to inspect before tearing into it much further.

Greg

[hotmansweep]

I second oil ring failure or head gasket

[Venom_Injected]

Piston rings out of context maybe (gap relation to each other)

High load, increase in oil PSI, and crankcase pressure..... its got a chance were it could sneak by a compression test.....


I say this assuming its an entirely new motor with wall finish to ring matched and that they were seated properly.....

[2FAST4U]

Originally Posted by Venom_Injected

Valve seals ?

That's my thought too

[DWIGHT]

you did not say what heads you have or the age. Or if the car was in storage for a few years, but

last summer a buddy brought me his new purchased 8 year old Cobra with 11,000 miles on it. 351W with iron heads. It had not run much in a couple of years.

Same problem you have.

I replaced the valve seal with out pulling the heads off. Maybe two hours. I used a special hose screwed into the spark plug hole to blow air into to keep the valve up while I removed the keeper and retainer.
Pulled the old seal off and install the new one. Easy.

Solved the smoking problem.

Then he bought a Keith Craft 525 hp 408 stroker and had me swap motors.

Dwight

P.S. I have a 351W for sale

[Venom_Injected]

Originally Posted by 2FAST4U

That's my thought too

I didnt read too well before and Greg nailed it.... a valve seal leak would be a bit more constant and be on hot idle / long duration idle instances....
(And not on hard accel)
(Not to say this couldn't be it though)


If its bothering you....a leakdown test on the suspects maybe? (To at least disprove the rings and guides)

If you pass a leak down....
V V V V V V V V V V V V V V V
For a cheap trial (vs. pulling the heads) go and buy 4 valve seals for the 2 suspected cylinders (And keepers too).... and apply some PSI in the cylinders to prevent valves dropping in.... pull the springs(get an on-motor puller), replace the seals and give it a twirl... probably the cheapest vs. pulling the heads... (you can also throw one peice nylon rope inside the cylinder and bring to TDC)

TFS valve seals 'CAN' be known for this upon research (which I noticed when I put my tfs1 cam and valve spring kit on my gt40ps) Or so the mustang forums say....

[Luthersnake]

Replace the intake gaskets...bet its sucking oil from the valley....doesn't take much....

[Jack Wojack]

I have what appears to be the same situation on a new FRPP short block (600 miles). Like you I thought I was sucking oil vapor into the manifold through the PCV hose. Re-routed a gutted PCV valve to the filter base however the issue seems to continue. ONLY the Left Side. Now I need to go deeper.


I will follow the above suggestions and watch this post.

Jack

[ROADRACER83]

I really think that you have a couple of oil rings (or more) that have failed to seat properly or a small leak in the intake manifold gaskets. The rings may be installed with all the gaps lined up instead of clocked at 120 degrees like they should be or the gaps are too big. It can happen if the engine builder uses standard rings in an engine with a slight clean up/blueprint overbore.

Those problems will show up in low manifold vacuum conditions like WOT. Oil in the PCV system will usually show up on all cylinders and you will have oil in the hose to the carb base and in the intake manifold runners.

Valve seal leaks almost always show symptoms on high vacuum conditions such as idle or de-acceleration where the oil is sucked down the valve stem. Good readings on a compression test can simply indicate that the compression rings are good or that you have a little oil in all cylinders.

To make sure the rings seat on new or bebuilt engines, some engine builders recommend using a petroleum oil for the first 500 or 1000 miles and then change to synthetic to ensure the rings break in.

Ron

[Greg_M]

So the consensus is the following in order of least difficulty:

1. valve stem seal check
2. instake gasket swap
3. head gasket problem
4. oil control ring problem.

With a possiblity of a PCV problem but not as likely since it should effect all cylinders.

[tirod]

Preparatory to a leak down, do a compression check. If you find weaker cylinders, squirt oil in them, see if it comes up. If it does - rings, if not - valves at the seat.

It may or may not pin point things, it will give more data, it's cheap and "non-invasive."

[jdl902]

Thanks for the thoughts guys; I especially hadn't thought of a bad oil control ring alone. The heads were new and the block had been freshly bored for new pistons and rings.

I'm skeptical of an intake leak because the smoke comes on at WOT (low vacuum) and not idle when vacuum is greatest. I may be missing something here. However since it's easy I'm going to borrow a borescope from work and take a look at the intake/head joint and look for gasket problems or oil puddles. I've learned these Edelbrock intakes are very poorly finished so it could be the intake gasket. I guess while I'm at it I'll see if I can inspect the cylinders for damage (not sure if the scope fits in the plug hole).

After that I'll try to get my hands on a leakdown tester and if that tells me nothing new then I'll try new guide seals for fun since it's cheap and easy. If that fails then I'll have nothing left to do but a teardown (that would be a good excuse to get a stroker kit I suppose).

I think one of the keys is the fact that the bad smoke is on hard aceleration. I'm not sure what exactly that means but once I have this licked it will be obvious

[jdl902]

So a simple test solved the problem by forcing a teardown A peak in the cylinders with a borescope seemed to show some oil on the walls leaking from above, "must be the guide seals". Hoping this was the case since it's the cheapest and simplest option, I bought new seals. Since my new leakdown tester hadn't arrived and I didn't have fittings to pressurize the cylinder I fell back on the tried and true "stuff a rope through the plug hole" to remove the springs. Except when I go to remove the rope, it has somehow knotted itself and will not come out. It's not hanging up on the valves or jammed in a ring landing, I can't slide a tube over it, it's knotted itself!

I've found a few posts on the internet where this fate has befallen others so I guess this week is not my time to buy a lottery ticket. I'll have to pull the head, which gives me an excuse to clean up all the deposits this burning problem has caused. It also forces me to change the intake gasket and while I'm in there, for the price of rod bearings and rings I might as well replace the rings on the two bad cylinders. In the end I'll have addressed nearly every possible issue so I better not have anymore smoke!

I'll be getting the parts tomorrow and will try to remember to post a picture of the knot for anyone who wants to try to replicate my feat.

[convincor]

What intake gaskets used?

[PKingsley]

I just replaced my valve seals and don't see how that rope trick can ever work. I needed the internal pressure to hold the valve up stiff so I could break the spring hat free from the split keepers when compressing the spring. With rope in there the valve would have just squished down with the spring and I'd never get the keepers off. Also with a tee fitting and a few adapters you can rig a standard compression tester to push in air. A little late now for you unfortunately. Looks like you've got your work cut out for you. I'd recommend using viton valve seals. My car smoked like a chimney before I put the new seals in and now it's fine.

[jdl902]

I'm using the 1250S3 intake gasket but have my doubts that this was the source of my problem because I didn't see a vacuum on the dipstick tube and I couldn't see any leaks with a borescope.

I've used the rope trick in the past and it works, but not so well if you can't get the rope out of the cylinder My compression tester had a swaged on end so it wasn't of any help. I'm going to try Comp Cams seals, seems a few people have had problems with the seals on Trickflow heads.

[jdl902]

I'm knot a happy camper.

[jdl902]

So I'm into the teardown now and the intake and head gaskets look fine. The remaining suspects seem to be valve guides/seals and piston rings. None of the valves are particularly clean, I started tracing my smoke problems by fixing a problem with the PCV sucking oil in a poorly baffled valve cover, but my two oily plugs correspond to the two dirtiest sets of valves. The fact that the intake valve has bad deposits on the face and backside seems to suggest the oil has to be coming in from above

I'm still considering putting new rings on the bad cylinders while everything is apart but I'm also cautious of causing new problems while fixing things that aren't broken. I'm tempted to pull the pistons out of the two bad cylinders (the bores look good for what it's worth) but will a ring problem be visible to inspection? The crosshatch is still visible (only about 3,000 miles since boring over) do I need to run a hone through to break the glaze? Tom Monroe's book suggests this is optional for moly rings. I'm cautious that if I replace perfectly good rings there's a chance the new ones won't set and I may have caused a new problem.

In the meantime I'm going to take the heads to a machine shop to have the valve guides accurately measured.

A bad cylinder




A less bad cylinder (I think the deposits are from my PCV issues).

[CraigS]

It is tempting to cover all bets while the heads are off and rering those two cylinders. But I just don't see rings causing oil buildup on the top side of the intake valves.That oil is either from the guide seals or from the intake.

[canuck1]

I'm not an expert, but I tend to concur with Craig. Your symptoms as well as your earlier compression tests do not point directly to the rings not sealing.

I would not go into the shortblock but get the valves & guides checked, replace seals and reassemble. Our summer is too short to dig any further now anyways .

Once it's back together make sure you double check pushrod length to ensure good valve stem tip to rocker arm sweep/contact. This can be a real valve guide killer if it isn't just right.

Good luck.

Sean

[RET_COP]

I have the same situation. Brand new heads Brodix KC 195s. I noticed a little oil shine on plug inspection. Pulled the carb and noticed oil shine on the plenum. I though Intake Gasket. I pulled the intake and all runners had oil shine. I changed the gasket, even used Ultra blue around the intake ports and the bottom of the gasket. Ran the car for a while and noticed the same thing. I put a oil separator on the pcv line and saw after a week of cruise nights oil had accumulated maybe an ounce or less. hmmm. could this be enough oil? then I hammered the car for a week up and down the rpm range, alot of deceleration and checked the separator. Bingo more oil than before. Anyway I pulled the heads as I wanted to try some thinner gaskets (cometics) when I noticed the back of the intake valves. They looked the same as the pictures in this thread!!! some worse than others. I took the valves out and scraped them and cleaned everything. The black goo was soft so it cleaned real nice but it would have been tough with the heads on the car. Now I believe this was from my pcv problem that was solved but let me ask you this. Could it be that I have too much blow by causing turbulence in the valve covers causing excessive oil to get by the baffles and into the pcv system? This I will investigate further when I get the heads back together . I will post my results to help out with this thread. I believe everyone should have an oil separator in their pcv line, I'm sold on it and will by a better one for my car.
Lou

[jdl902]

Well my machinist said the guides are good and the seals looked good. He pulled half the seals so I guess I'll be replacing those.

While I'm at it he said there should be no problem pulling the pistons for inspection, and if the ring seems to be worn or broken, replacing the rings without honing (they're moly rings and I only have 3,000 miles on since boring). He agreed that if it was an oil control ring the compression test wouldn't have shown it. Also gave me a good tip for checking the pistons; the top should have some soot coverage, if the outer edge of the top face is clean that can be a sign that oil is getting by the rings and washing the top of the piston off.

So I'll probably pull the bad cylinders for a closer look while I'm in there. I also plan to swap the heads from right to left. If I still have oily plugs after all this work I'll see if they are the same cylinder or if they follow the "bad" head.

Our summers are definitely too short! But I want to lick this problem before doing much more driving; cleaning up all of these oil deposits has me wishing that I had paid more attention to the problem when it first started.

[Jack Wojack]

Lou, what engine do you have?

I am of the same belief that a oil separator or a better valve cover baffle under the PCV valve is in order. I am working the baffle route now.

Jack

[RET_COP]

Jack I have a 351w with Cobra aluminum/Black valve covers. There is one rectangular plate over the breather holes in the cover. I wouldn't really call it a good baffle, it just keeps a direst shot of misty oil from going in the pcv system. A real baffle would be great, your on the right track.
Lou